US20190135897A1 - Crystal Structures Comprising Elastin-Like Peptides - Google Patents

Crystal Structures Comprising Elastin-Like Peptides Download PDF

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US20190135897A1
US20190135897A1 US16/089,492 US201716089492A US2019135897A1 US 20190135897 A1 US20190135897 A1 US 20190135897A1 US 201716089492 A US201716089492 A US 201716089492A US 2019135897 A1 US2019135897 A1 US 2019135897A1
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xaa
membrane
vpgig
seq
elp
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Sherif Ahmed Abdelsalam Elsharkawy
Maisoon Al-Jawad
Alvaro Mata Chavarria
Esther Tejeda-Montes
Roxanna Sharon Ramnarine Sanchez
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Mintech V LLC
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Queen Mary University of London
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
    • C07K14/78—Connective tissue peptides, e.g. collagen, elastin, laminin, fibronectin, vitronectin or cold insoluble globulin [CIG]
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/54—Organic compounds
    • C30B29/58—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • C30B7/02—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions by evaporation of the solvent
    • C30B7/04—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions by evaporation of the solvent using aqueous solvents
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides

Definitions

  • the present invention relates to new biomimetic mineralized apatite structures.
  • the present invention also relates to processes for the production of new biomimetic mineralized apatite structures based on natural and synthetic protein scaffolds.
  • Dental enamel has a distinctive hierarchical organization that generates its remarkable toughness, wear resistance, and critical role in tooth function (Boyde, A. Microstructure of enamel. CIBA Foundation Symposia, 18-31 (1997). At the molecular level, enamel is 97% by weight carbonated hydroxyapatite (HAp) (the rest being organic matrix and water) (Elliott, J. C. Structure, crystal chemistry and density of enamel apatites. CIBA Foundation Symposia, 54-72 (1997)) with different ionic substitutions in the lattice according to location (Robinson, C., Weatherell, J. A. & Hallsworth, A.
  • HAp carbonated hydroxyapatite
  • HAp forms well-defined and aligned crystals that are about 70 nm wide, 25 nm thick, and might extend across the full width of enamel (Boyde, A. Microstructure of enamel. CIBA Foundation Symposia, 18-31 (1997). Groups of about 1000 of these crystallites come together to create well-organized microscopic prisms of about 5 ⁇ m in diameter (Elliott, J. C. Structure, crystal chemistry and density of enamel apatites. CIBA Foundation Symposia, 54-72 (1997)).
  • Organic matrices control the biomineralization of dental hard tissues.
  • self-assembling nanospheres of amelogenin act as a structural framework that is thought to precisely guide crystal growth in specific directions (Fincham, A. G. et al. Evidence for amelogenin ‘nanospheres’ as functional components of secretory-stage enamel matrix. Journal of Structural Biology 115, 50-59 (1995)).
  • self-assembling methodologies based on recombinant amelogenin to mimic biomineralization (Ruan, Q., Zhang, Y., Yang, X., Nutt, S. & Moradian-Oldak, J.
  • amelogenin-chitosan matrix promotes assembly of an enamel-like layer with a dense interface.
  • Acta Biomaterialia 9, 7289-7297 (2013) poly(amido amine)-type (PAMAM) dendrimers as analogues to amelogenin (Wu, D. et al. Hydroxyapatite-anchored dendrimer for in situ remineralization of human tooth enamel. Biomaterials 34, 5036-5047 (2013)), peptide amphiphile nanofibres to stimulate cell-based therapies (Huang, Z. et al. Bioactive nanofibers instruct cells to proliferate and differentiate during enamel regeneration.
  • Elastin-like polypeptides have been used as bioactive building-blocks of materials and can easily incorporate bioactive epitopes to provide specific functionality (Panitch, A., Yamaoka, T., Fournier, M. J., Mason, T. L. & Tirrell, D. A. Design and Biosynthesis of Elastin-like Artificial Extracellular Matrix Proteins Containing Periodically Spaced Fibronectin CS5 Domains. Macromolecules 32, 1701-1703 (1999)) such as RGDS to promote cell adhesion (Nicol, A., Gowda, C. & Urry, D. W. Elastic protein-based polymers as cell attachment matrices.
  • statherin-derived peptide DDDEEKFLRRIGRFG to promote mineralisation
  • statherin Dependence on sequence, charge, hydrogen bonding potency, and helical conformation for adsorption to hydroxyapatite and inhibition of mineralization. J Biol Chem 267, 5968-5976 (1992)). While ELPs containing this statherin-derived peptide have been used in fabricating membranes for periosteal regeneration (Tejeda-Montes, E. et al. Mineralization and bone regeneration using a bioactive elastin-like recombinamer membrane. Biomaterials 35, 8339-8347 (2014)) and implant coatings (Li, Y. et al.
  • the present inventors have surprisingly found a novel hybrid organic-inorganic system based on protein scaffold membranes that is able to grow hierarchically-ordered apatite crystalline structures that resemble those found in natural dental enamel, in both hierarchical organization and chemical composition.
  • a synthetic crystal having a hierarchical structure formed on a protein scaffold membrane.
  • a process for producing hierarchically ordered crystal structures comprising the step of contacting a protein scaffold membrane with a solution of mineralizing ions.
  • the contacting step may be performed at physiological pH and temperature.
  • the invention also extends to synthetic crystals obtainable by such methods.
  • a synthetic crystal of the invention for use in medicine, such as for use in the prevention and/or treatment of demineralisation of teeth or dental disease or dental hypersensitivity.
  • a synthetic crystal of the invention for use in the prevention and/or treatment of bone demineralisation, low bone density and/or osteoporosis.
  • a synthetic crystal of the invention for use in the prevention and/or treatment of bone disease.
  • a synthetic crystal of the invention for use in the prevention and/or treatment of a bone defect.
  • a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention of bone demineralisation, low bone density and/or osteoporosis.
  • a method of treatment of or prevention of demineralisation of teeth or dental disease or tooth hypersensitivity in a subject comprising administration to the subject a synthetic crystal of the invention.
  • a method of treatment of or prevention of bone demineralisation, low bone density or osteoporosis in a subject comprising administration to the subject a synthetic crystal of the invention.
  • a method of treatment of or prevention of bone disease in a subject comprising administration to the subject a synthetic crystal of the invention.
  • a method of treatment of or prevention of bone defect comprising administration to the subject a synthetic crystal of the invention.
  • a medical implant such as a dental implant, comprising the synthetic crystal of the invention, and methods for implantation of such devices.
  • a bone implant comprising the synthetic crystal of the invention, and methods for implantation of such devices.
  • FIG. 1 Morphological, mechanical and chemical description of hierarchically-ordered mineralized structures on the surface of the membranes.
  • FIG. 2 Table showing the different ELP molecules along with isoelectric points and molecular weights. Bioactive sequences are shown in red. Schematics at the bottom, illustrating the fabrication and mineralization processes.
  • FIG. 3 SEM images of the crystal morphology on; a) uncoated borosilicate glass showing the characteristic needle-like and ball-like morphology; and borosilicate glass coated with ELPs b) statherin-ELP, and c) RGDS-rich ELP showing flat plate-like crystals. Similarly collagen membranes showed disordered crystal growth (d).
  • FIG. 4 SEM image showing the growth of the hierarchical mineralized structures on both sides of the RGDS-rich ELP membranes. Below images showing a side view of the structures with different heights.
  • FIG. 5 EDX mapping (top) of the structures showing the presence of calcium, phosphorus, and fluoride with atomic ratios similar to stoichiometric apatite crystals and dental hard tissues.
  • Fourier transform infra-red (FTIR) spectroscopy analysis (below) which revealed spectra exhibiting amide peaks before undergoing mineralization (corresponding to the statherin-rich ELP material), while after mineralization they exhibited hydroxyl-free apatite peaks.
  • FTIR Fourier transform infra-red
  • FIG. 6 SEM images of RGDS-ELP membranes, when mineralised without the use of fluoride, showing a similar hierarchical organization with those formed with fluorine. However, the morphology of nanocrystals changed to elongated plate-like due to the different chemistry. We are not restricted in using fluorine to grow the structures; we can grow them in a fluorine free conditions.
  • FIG. 7 a) BSE images showing brighter areas at the centre of the structures that indicate the presence of mineral deep within the membrane. b) FIB sectioning of the hierarchically mineralized structure on RGDS-ELP resolving the deeper mineralized core structures located underneath the centre of the structures. c) Cross-section of the RGDS-ELP membrane after 8 days of mineralization showing the two different morphologies found within the bulk; enamel prism-like (e) and round structures (f) found within the membrane and suggesting the presence of ionic gradient. d) EDX mapping at the same area of the SEM image (c), near the surface of the membrane, calcium, phosphorus, fluoride, and oxygen are abundant representing the enamel prism-like crystalline structures.
  • FIG. 8 3D reconstruction of serial FIB-SEM imaging.
  • the angle of visualization is modified in order to be able look at the structures from within the membrane, which also clearly shows the core structure at the centre (left).
  • Scanning electron microscopy (SEM) using the backscattered electron mode (BSE) and focused ion beam (FIB) revealed that the mineralized structures exhibit a mineralized core deep within the membrane made from similar elongated and aligned nanocrystals (right).
  • FIG. 9 Series of SEM images (1-6) showing the procedures followed to prepare the samples for the TEM liftout using FIB.
  • the lamella is thinned down in order to be transmitting electrons through using the TEM for structural and crystallographic information (7).
  • FIG. 10 SEM images showing the nucleation and crystal growth within the bulk of the organic matrix revealed different structures. Round structures exhibiting a dense pattern of regular granular regions were observed deep within the bulk of the membrane while core structures made from nanocrystals oriented at 102 ⁇ 6° with respect to the surface of the membrane were observed nearer the surface. It is possible that these two types of structures represent different stages of development of the mineralized cores, suggesting the presence of an ionic gradient across the cross-section of the organic matrix.
  • FIG. 11 Closer examination using DDC-SEM and EDX spectral mapping of both of these structures revealed a thin less dense material (green) surrounding a denser (orange) material.
  • the less dense material was found to be rich in carbon, oxygen, and nitrogen, which is commonly found in organic material.
  • the denser material exhibited abundance of calcium and phosphorus, which reflects its inorganic nature.
  • FIG. 12 SEM and BSE images taken simultaneously from same area to allow density-dependent analyses (DDC-SEM). BSE images show clearly the disappearance of the thin coating around the crystals giving an indication of the presence of the less dense material surrounding the crystals. The less dense material is confirmed in to be rich of carbon, nitrogen and oxygen, giving indication of its organic nature according to EDX data ( FIG. 11 ).
  • FIG. 13 a ) Time-lapse microscopy demonstrating the emergence and centripetal growth of the structures by phase contrast imaging. b) DDC-SEM images of day 1, 2, and 8 at different size scales, demonstrating that the structures gain hierarchical definition as a function of time. The accumulation of the less-dense material (green) is clearly observed at the interprismatic areas at the different time-points. c) Graphs showing the increase in volume during the morphogenesis of the hierarchical mineralized structures (left) and the significant improve of the stiffness as a function of time (right).
  • Ion selective electrode (ISE) measurements and SEM images showing the free ion concentration in the system as a function of time with (bottom) or without (top) the use of the BIS-TRIS buffer (top), that controls the pH of the system, the system reaches steady-state conditions earlier under constant pH, and hence more calcium consumption, faster mineralization, and larger mineralized structures (bottom) up to almost 1 mm in diameter.
  • XRD at different timepoints clearly shows the phase transformation. Brushite (B) is observed during the first hour of the mineralization, while it starts to dissolve by time transforming into the more stable phase of Fluorapatite (F) after the first day.
  • FIG. 14 The time-dependent mineralisation and growth behaviour of the structures on the membrane surface were traced in real-time using time-lapse phase-contrast optical microscopy and demonstrated an outward radial growth of the structures. As evidenced from the quantitative data, the structure starts to grow after about 5 hours of incubation, and then it passes through a quiescent state (between 5 to 10 hours) until a rapid growth stage takes place after 10 hours (arrow), subsequently growth takes a linear trend as a function of time.
  • FIG. 15 SEM images showing the progression of the centripetal growth of the hierarchical mineralized structures at different developmental stages (left to right).
  • FIG. 16 FIB-SEM analysis of RGDS-ELP revealed that the structures acquired hierarchical definition ( FIG. 3 b ) and volume as a function of time, respectively.
  • FIG. 17 ISE measurements during a) the first hour and b) after 48 hours.
  • a significant drop in the free calcium ion concentration from 10 mM (initial concentration) to about 3.7 mM is observed, while the fluoride concentration remains fairly constant (a slight drop from 2 mM to 1.9 mM).
  • the consumed calcium to fluoride ratio is about 7:0.1, giving an indication that the precipitated phase does not contain fluoride and therefore is not fluorapatite where the Ca:F ratio equals 10:6, rather another intermediate phase.
  • This intermediate phase has been identified as brushite using XRD and FTIR.
  • FIG. 18 FTIR spectra of the mineralizing statherin-ELP membrane at different timepoints (1 hour, 1 day, 2 days, and 8 days). At early timepoints, the spectra exhibit the characteristic sharp peak of HPO4-vibration characteristic to brushite (CaHPO4.2H2O) at 1238 cm-1, and OH stretching peak of water molecule of brushite. As a function of time, the % transmittance of the brushite peaks decrease at the expense of the apatite's phosphate peaks, this confirms that brushite is the intermediate crystalline phase before transformation to fluorapatite.
  • FIG. 19 SEM of images of mineralized membranes at different initial ionic concentrations ranging from 2.5-10.0 mM of Ca2+, 1.6-6.0 mM of PO43-, and 0.5-2.0 of F—, demonstrating that the hierarchical structures form in all conditions independently of the initial ionic strength.
  • FIG. 20 a ) Circular dichroism (CD) of the statherin-ELP molecule at 4, 25, and 37° C.; showing an increase in ⁇ -spiral population at the expense of the random-coils, above its inverse transition temperature. b) Dynamic light scattering showing both the hydrodynamic radii and zeta potential of the statherin-ELP in deionized water (left) and in 10 mM calcium solution (right), evidencing the strong calcium binding to the statherin-ELP polypeptides. c) SEM images of the mineralization of the membranes at different temperatures below (4 and 21° C.) and above the Tt (37° C.). The hierarchical mineralized structures were observed at temperatures above the Tt.
  • CD Circular dichroism
  • FIG. 21 SEM images of mineralized membranes at small increments of temperature to see the effect of the transition temperature of the molecules on the formation of the hierarchy.
  • FIG. 22 SEM images of mineralized membranes at different pH 4, 6, and 8.
  • FIG. 23 a Graphs showing of the stiffness of the unmineralized membranes fabricated with different ELP to crosslinker ratio (left), where a significant increase in the Young's moduli is observed with the highly crosslinked membranes in comparison to the less crosslinked membranes. As a result, the swelling measurements (right) evidence that the higher the stiffness (crosslinking), the lower the diffusion and swelling.
  • FIG. 24 Diffusion coefficients at different crosslinking ratios.
  • FIG. 25 The apatite chemical composition of the different organized structures, remains the same as evidenced by XRD at different crosslinking ratios. Note the increase in the number of the structures at high crosslinking.
  • FIG. 26 a ) Application of the in-situ cross-linked ELP membrane conformed over the rough and uneven surface of exposed human dentine, exhibiting the hierarchical mineralized structures as a coating on top of the native tissue. At closer magnification, the membranes were able to infiltrate, bind, and occlude the open dentinal tubules structures. b) FIB milling of the mineralized coating at different depths to observe the dentine-membrane interface, where the thickness of the coating is about 10 ⁇ m, at which it exhibits infiltration of nanocrystals emerging from the hierarchically organized structures grown from the ELP membrane, and in turn blockage of the dentinal tubules.
  • FIG. 27 XMT showing that the mineralized membrane can not only fill and occlude large cervical defects of teeth that are major cause for dentine hypersensitivity, but also with a high density of mineral.
  • FIG. 28 Effect of microfabricated topography on the growth of the hierarchical structures. Microfabricated topographies were used to tune the directionality of the structures. The structures can be asymmetrical in comparison to the symmetric circular structures on the surfaces. The crystal orientation changes at the 90° and 270°.
  • FIG. 29 Cell viability studies of Human adipose derived stem cells (hADSC) on the mineralized structures SEM images showing the extent of viability, spread, and attachment of the hADSCs on the hierarchical structures grown on SN-RGDS-ELP membrane at day 1 (a-b). At day 7, SEM and live-dead imaging showing the significant amount of viable cells on top of the mineralized structures as seen in confocal microscopy (b-c). e) SEM image that shows that the cells on the unmineralized membranes didn't spread in comparison to the mineralized on at day 7.
  • hADSC Human adipose derived stem cells
  • FIG. 30 Morphological description of hierarchically-ordered mineralized structures.
  • FIB sectioning of the hierarchically mineralized structures resolving the deeper root-like structures located underneath the centre of the circular structures and j) the nanocrystals within the ELP membrane and aligned perpendicular to the surface of the membrane.
  • FIG. 31 Chemical characterization of the highly-ordered mineralized structures.
  • FIG. 32 Growth of the hierarchically-ordered mineralized structures.
  • a,b Time-lapse microscopy demonstrating a) the emergence and centripetal growth of the structures by phase contrast imaging and b) their initial stages of organization at the surface of an ELP membrane by SEM imaging. Outward bursting and growth is evidenced by thickening of the advancing front (arrow).
  • c DDC-SEM images of day 1, 2, 4, and 8 at different size scales, demonstrating that the structures gain hierarchical definition as a function of time. The accumulation of the less-dense material is clearly observed at the interprismatic areas at the different time-points.
  • d Cross-section of an ELP membrane after 8 days of mineralization.
  • FIG. 33 Morphological comparison between the synthetic enamel-like hierarchically-ordered mineralized structures and human dental enamel. SEM images depicting the morphological similarities at different length-scales between the synthetic and natural tissues including a,e) apatite nanocrystals with similar crystal morphology, b-g) prism-like/interprism-like microstructures, and d,h) prism assemblies into macroscopic structures. The synthetic structures exhibit a centripetal pattern rather than the linear pattern that forms human dental enamel.
  • FIG. 34 Application of the hierarchically ordered enamel-like material on enamel and dentine.
  • FIG. 35 SEM images of the crystal morphology on; a) uncoated borosilicate glass showing the characteristic needle-like and ball-like morphology; and borosilicate glass coated with ELPs b) IK, c) SN, and d) RGDS showing flat plate-like crystals. Similarly e-f) collagen membranes showed disordered crystal growth.
  • FIG. 36 XRD at different timepoints clearly show the phase transformation.
  • Brushite (B) is observed during the first hour of the mineralisation, while it starts to dissolve by time transforming into the more stable phase of Fluorapatite (F) after the first day.
  • FIG. 37 FTIR spectra of the mineralising ELP membrane at different timepoints (1 hour, 3 hours, 1 day, 2, 4, and 8 days). At early timepoints, the spectra exhibit the characteristic sharp peak of OH bending of brushite (CaHPO4.2H2O) at 1238 cm-1, and OH stretching peak of water molecule of brushite. As a function of time, the % transmittance of the brushite peaks decrease at the expense of the apatite's phosphate peaks, this confirms that brushite is the intermediate crystalline phase before transformation to fluorapatite.
  • FIG. 38 ISE measurements during a) the first hour and b) after 48 hours.
  • a significant drop in the free calcium ion concentration from 10 mM (initial concentration) to about 3.7 mM is observed, while the fluoride concentration remains fairly constant (a slight drop from 2 mM to 1.9 mM).
  • the consumed calcium to fluoride ratio is about 7:0.1, giving an indication that the precipitated phase does not contain fluoride and therefore is not fluorapatite where the Ca:F ratio equals 10:6, rather another intermediate phase.
  • This intermediate phase has been identified as brushite using XRD and FTIR ( FIGS. 36 and 137 ).
  • FIG. 39 SEM and BSE images taken simultaneously from same area to allow density-dependent analyses (DDC-SEM). BSE images show clearly the disappearance of the thin coating around the crystals giving an indication of the presence of the less dense material surrounding the crystals. The less dense material is confirmed previously ( FIG. 32 ) to be rich of carbon, nitrogen and oxygen, giving indication of its organic nature.
  • a synthetic crystal having a hierarchal structure wherein the structure is formed on a protein scaffold membrane.
  • the synthetic crystals can also be referred to as artificial or synthetic dental enamel or artificial or synthetic bone.
  • a crystal is a homogeneous solid substance having a natural geometrically regular form with symmetrically arranged plane faces.
  • the synthetic crystal having a hierarchal structure is apatite.
  • Apatite refers to a phosphate mineral.
  • Apatites are flexible structures with wide range of optional substitutions that can happen in their lattice at both cation and anion positions; therefore have the general formula A 10 (BO n ) 6 X 2 (alternatively A 5 (BO n ) 3 X).
  • A is a divalent cation selected from the group comprising Ca 2+ , Sr 2+ , Ba 2+ and Pb 2+ .
  • BOn is an anionic complex, such as an anionic complex selected from the group comprising PO 4 3 ⁇ , AsO 4 3 ⁇ , VO 4 3 ⁇ or CO 3 2 .
  • X is generally an anion.
  • X is selected from the group comprising OH, F and Cl.
  • the apatite has the formula Ca 5 (PO 4 ) 3 F.
  • Apatites have hexagonal crystallographic symmetry.
  • the space group of apatites is usually (P6 3 /m) where the 6-fold c-axis is perpendicular to 3 a-axes at 120° to one another with some lower symmetry analogues.
  • the apatite is selected from the group comprising fluroapatite, hydroxyapatite and chlorapatite.
  • the apatite is fluorapatite.
  • Fluroapatite is a phosphate mineral with the general formula Ca 5 (PO 4 ) 3 F. Fluroapatite is alternatively referred to as Ca 10 (PO 4 )F 2 or FAp.
  • the apatite is hydroxyapatite.
  • Hydroxyapatite is a phosphate mineral with the general formula Ca 5 (PO 4 ) 3 (OH).
  • the apatite is chlorapatite.
  • Chlorapatite is a phosphate mineral with the general formula Ca 5 (PO 4 ) 3 Cl.
  • the apatite is flurohydroxyapatite.
  • the apatite is fluorapatite.
  • the scaffold membrane is formed from a material with high mineralizing properties, i.e. the material is able to convert the components of a solution into a mineral.
  • the scaffold membrane is selected from the group consisting of a chitin, gelatine, polyacrylamide, alginate, poly-lactic acid, poly-glycolic acid, poly-lysine polymer, collagen, amelogenin, silk, chitosan, elastin or elastin-like membrane.
  • the membrane is formed of natural elastin.
  • the natural elastin comprises a pentapeptide selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXX, XGXX, XXGXX, XXGX, XXXG), wherein X is any amino acid.
  • the natural elastin comprises at least one pentapeptide selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXX, XGXX, XXGXX, XXXGX, XXXXG), wherein X is any amino acid.
  • the natural elastin comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten pentapepetides selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXXX, XGXX, XXGXX, XXGX, XXXG), wherein X is any amino acid.
  • X is an amino acid selected from the group consisting of V, P, G, S, F and I.
  • the natural elastin comprises a pentapeptide selected from the group consisting of (Gly-X-X-X-X)y, (X-Gly-X-X)y, (X-X-Gly-X-X)y, (X-X-X-Gly-X)y and (X-X-X-X-Gly)y, wherein X is any amino acid and wherein y is the number of repeats. For example, y may be at least 5 or at least 10.
  • the natural elastin comprises the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • the natural elastin comprises at least one tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline. In one embodiment, the natural elastin comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • X is an amino acid selected from the group consisting of V, P, G, S, F and I
  • the natural elastin comprises the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG)y, where X is any amino acid apart from proline and wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • the natural elastin comprises the tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG). In one embodiment, the natural elastin comprises at least one tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG). In one embodiment, the natural elastin comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Pro-Gly-Ile-Pro-Gly (PGIPG).
  • PGIPG tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly
  • the natural elastin comprises the tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • the natural elastin comprises the tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG). In one embodiment, the natural elastin comprises at least one tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG). In one embodiment, the natural elastin comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Pro-Val-Gly-Ser-Gly (PVGSG).
  • the natural elastin comprises the tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • the natural elastin comprises the tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG). In one embodiment, the natural elastin comprises at least one tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG). In one embodiment, the natural elastin comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Val-Gly-Phe-Pro-Gly (VGFPG).
  • the natural elastin comprises the tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • natural elastin membrane is tuneable and can include numerous modifications based on the pentapeptide containing glycine or the pentapeptides (VPGXG), (PGIPG), (PVGSG) and (VGFPG).
  • the membrane is an Elastin-like protein membrane or Elastin-like protein hydrogel.
  • Elastin-like protein membrane can also be a hydrogel.
  • Elastin-like proteins are recombinant polymers that exhibit comparable biological and mechanical properties to natural elastin. These polymers have generated great interest due to their modular structure, biocompatibility, biodegradability, ease of design and production, and capacity to be synthesised with a high level of molecular control and tuneability. ELPs allow for tuneable molecular design.
  • the term elastin-like protein is interchangeable with the term elastin-like polypeptide, elastin-like polymer and elastin-like recombinamers.
  • the membrane is formed of Elastin-like protein membrane or Elastin-like protein hydrogel.
  • the ELP membrane or hydrogel comprises a pentapeptide selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXX, XGXXX, XXGXX, XXGX, XXXG), wherein X is any amino acid.
  • the ELP membrane or hydrogel comprises at least one pentapeptide selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXX, XGXX, XXGXX, XXXGX, XXXXG), wherein X is any amino acid.
  • X is an amino acid selected from the group consisting of V, P, G, S, F and I.
  • the ELP membrane or hydrogel comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten pentapepetides selected from the group consisting of Gly-X-X-X-X, X-Gly-X-X, X-X-Gly-X-X, X-X-X-Gly-X and X-X-X-X-Gly, (GXXXX, XGXX, XXGXX, XXGX, XXXG), wherein X is any amino acid.
  • the ELP membrane or hydrogel comprises a pentapeptide selected from the group consisting of (Gly-X-X-X-X)y, (X-Gly-X-X)y, (X-X-Gly-X-X)y, (X-X-X-Gly-X)y and (X-X-X-X-Gly)y, wherein X is any amino acid and wherein y is the number of repeats.
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • the ELP membrane or hydrogel comprises at least one tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline. In one embodiment, the ELP membrane or hydrogel comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG)y, where X is any amino acid apart from proline and wherein y is the number of repeats.
  • y may be at least 5 or at least 10. In some embodiments, y is 1 or more, in particular when the peptide is cross-linked.
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG). In one embodiment, the ELP membrane or hydrogel comprises at least one tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG). In one embodiment, the ELP membrane or hydrogel comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Pro-Gly-Ile-Pro-Gly (PGIPG).
  • PGIPG tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Pro-Gly-Ile-Pro-Gly (PGIPG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG). In one embodiment, the ELP membrane or hydrogel comprises at least one tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG). In one embodiment, the ELP membrane or hydrogel comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Pro-Val-Gly-Ser-Gly (PVGSG).
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Pro-Val-Gly-Ser-Gly (PVGSG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG). In one embodiment, the ELP membrane or hydrogel comprises at least one tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG). In one embodiment, the ELP membrane or hydrogel comprises at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or at least ten tropoelastin recurrent motifs Val-Gly-Phe-Pro-Gly (VGFPG).
  • the ELP membrane or hydrogel comprises the tropoelastin recurrent motif Val-Gly-Phe-Pro-Gly (VGFPG)y, wherein y is the number of repeats.
  • y may be at least 5 or at least 10.
  • y is 1 or more, in particular when the peptide is cross-linked.
  • an ELP membrane or hydrogel is tuneable and can include numerous modifications based on the pentapeptide containing glycine or the pentapeptides (VPGXG), (PGIPG), (PVGSG) and (VGFPG).
  • ELP membranes are membranes formed of ELPs. ELP membranes can be generated using standard methods, for example as described in Tejeda-Montes et al., 2012.
  • the ELP membrane or hydrogel is cross-linked by a cross-linker.
  • a cross-linker is an inorganic or organic reagent that reacts with either a carboxylic group or an amine group of an ELP membrane or hydrogel, protein, polymer, peptide or amino acid through covalent bonds, or non-covalent bonds such as electrostatic, hydrogen bonds, or Van der Waals.
  • the degree of cross-linking can determine the stiffness of the ELP membrane and can be used to tune the morphology or organisation of the hierarchal structures. By increasing the degree of cross-linking in an ELP membrane, and therefore the stiffness of the ELP membrane, the ELP membranes will exhibit a higher degree of hierarchally organized structures.
  • the ELP membrane or hydrogel can be cross-linked by chemical cross-linking, enzymatic cross-linking by tissue transglutaminase, photoinitiated and/or ⁇ -irradation cross-linking
  • the ELP membrane or hydrogel has a cross linker ratio of greater than about 0.1, about 0.2, or about 0.25. In some emodiments, the cross linker ratio is up to about 50, or up to about 30 or up to about 25, or up to about 20. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of between about 0.25 to 24. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of between about 0.25 to 20.
  • the ELP membrane or hydrogel has a cross linker ratio of about 0.5 to about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of about 6 to 12. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of greater than about 0.25. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of between about 0.25 to 24.
  • the cross-linker ratio is the ratio of the molar concentration of cross-linker to the molar concentration of amine or carboxylic groups of the ELP membrane or hydrogel, protein, polymer, peptide or amino acid.
  • the ELP membrane or hydrogel has a cross linker to lysine ratio of between about 0.25 to 20. In a preferred embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of about 0.5 to about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of about 6 to 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of about 12. In one embodiment the cross-linker is hexamethyl diisocyanate. Young's modulus (or Elastic modulus) values can provide a measure of the stiffness of a solid material. The synthetic crystals of the invention have been found to have higher stiffness, in particular higher Young's modulus values.
  • the synthetic crystals of the invention have a stiffness, in particular Young's modulus values. that are comparable to sapphire. Young's modulus values can be measured using nanoindentation or atomic force microscopy (AFM) nanoindentation.
  • the synthetic crystal has a Young's modulus value of at least about 30, at least about 40, at least about 50, in particular at least about 60, or at least about 70, or at least about 80, or at least about 90, or at least about 100 MPa.
  • the synthetic crystal has a Young's modulus value of up to about 300, up to about 250 or up to about 200 MPa.
  • the synthetic crystal has a Young's modulus value of from 70 to 190 MPa. In one embodiment, the synthetic crystal has a Young's modulus value of from 90 to 170 MPa. In one embodiment, the synthetic crystal has a Young's modulus value of from 110 to 180 MPa. In one embodiment, the synthetic crystal has a Young's modulus value of from 120 to 140 MPa. In one embodiment, the Young's modulus value is measured using AFM nanoindentation. For comparison, the Young's modulus value for enamel is approximately 40 to 50 MPa when using AFM nanoindentation.
  • the synthetic crystal develops a hierarchical structure as a function of time.
  • the synthetic crystal has a Young's modulus value of between 70 and 190 MPa following 6 to 10 days mineralization.
  • the synthetic crystal has a Young's modulus value of between 90 and 170 MPa following 6 to 10 days mineralization.
  • the synthetic crystal has a Young's modulus value of between 110 and 180 MPa following 6 to 10 days mineralization.
  • the synthetic crystal has a Young's modulus value of between 120 and 140 MPa following 6 to 10 days mineralization.
  • the ELP membrane or hydrogel comprises a negatively charged or a neutral charge molecule.
  • the ELP membrane or hydrogel is substantially non-porous. In one embodiment, the ELP membrane or hydrogel comprises pores or micropores. In one embodiment, the ELP membrane of hydrogel comprises pores less than about 30 microns in diameter.
  • the scaffold membrane in particular the ELP membrane or hydrogel, can include various peptide sequences.
  • the peptide sequence is selected from the group consisting of
  • the peptide sequence is MGSSHHHHHHSSGLVPRGSHMESLLP-[VPGIGVPGIGVPGKGVPGIGVPGIGVPGIGVPGIGVPGKGVPGIGVPGIGAVTGRGDSPASSVPGIGVPGIG VPGKGVPGIGVPGIGVPGIGVPGIGVPGKGVPGIGVPGIG]6-V.
  • the scaffold membrane in particular the ELP membrane or hydrogel, can include bioactive sequences.
  • the bioactive sequence is MGSSHHHHHHSSGLVPRGSHMESLLP-[[(VPGIG) 2 (VPGKG)(VPGIG) 2 ] 2 AVTGRGDSPASS[(VPGIG) 2 (VPGKG)(VPGIG) 2 ] 2 ] 6 .
  • the bioactive sequence is RGDS. RGDS promotes cell adhesion.
  • the bioactive sequence is statherin-derived peptide DDDEEKFLRRIGRFG.
  • Statherin is a salivary protein that naturally acts as a chelating agent for calcium ions in order to enhance enamel remineralization during acid attacks.
  • the ELP membrane or hydrogel may comprise a bioactive sequence selected from the group consisting of MGSSHHHHHHSSGLVPRGSHMESLLP-[[(VPGIG) 2 (VPGKG)(VPGIG) 2 ] 2 AVTGRGDSPASS[(VPGIG) 2 (VPGKG)(VPGIG) 2 ] 2 ] 6 , RGDS or DDDEEKFLRRIGRFG.
  • the ELP membrane or hydrogel comprises one or more bioactive sequence.
  • the ELP membrane or hydrogel comprises two or more bioactive sequences. The skilled person would understand other bioactive epitopes can be incorporated into the ELP membrane to provide specific functionality.
  • the ELP membrane or hydrogel comprises a bioactive sequence as defined in Table 1.
  • the ELP membrane or hydrogel comprises collagen, amelogenin, bone sialoprotein, enamelin or phosphorylated serine.
  • the ELP membrane or hydrogel comprises graphene, carbon nanotubules, and/or quantum dots.
  • the ELP membrane or hydrogel comprises sugar, proteins, inorganic particles and/or peptides. The skilled person would understand that a wide range of solvent soluble materials can be incorporated into the ELP membrane.
  • the ELP membrane or hydrogel is biocompatible, i.e—it is not harmful or toxic to living tissue. In one embodiment, the ELP membrane or hydrogel is formed from a flexible material.
  • the ELP membrane or hydrogel has a ⁇ -spiral conformation.
  • the presence of a ⁇ -spiral conformation can be confirmed using circular dichroism (CD) spectroscopy.
  • ELP membranes or hydrogels exhibit reversible-phase behaviour and undergo inverse temperature transition (Urry 1992, 1997).
  • An ELP membrane will be in a disorganised state and will be highly soluble in aqueous solution below the transition temperature.
  • the transition temperature is the temperature at which a substance acquires or loses a distinctive property, for example changing from one crystal state to another.
  • An ELP membrane will transition to an organised, hierarchal crystal structure comprising ⁇ -spiral conformations above the inverse transition temperature.
  • the skilled person would understand that the inverse transition temperature will vary dependent on the type of membrane or hydrogel.
  • the ELP membrane or hydrogel has a ⁇ -spiral conformation when hierarchical mineralization takes place above the inverse transition temperature of the ELP membrane. The presence of a ⁇ -spiral conformation can be confirmed using circular dichroism (CD) spectroscopy.
  • CD circular dichroism
  • the inverse transition temperature of the ELP membrane is 10° C. to 90° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 33° C. to 41° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 35° C. to 39° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 37° C.
  • the inventors of the present invention are able to tune the directionality of growth of crystals with hierarchical structure using membranes with fabricated topographies.
  • the geometry of the topography can be used to change the directionality and shape of the crystalline structures.
  • the scaffold membrane is a fabricated membrane. In one embodiment, the scaffold membrane is a nanofabricated membrane, a microfabricated membrane or a macrofabricated membrane. In a preferred embodiment, the scaffold membrane is a microfabricated membrane.
  • the fabricated membrane can have a channelled topography (i.e. it comprises channels).
  • the arrangement and direction of the channels can be used to direct growth of the synthetic crystal structure.
  • the channels are co-planar (or substantially co-planar) with the surface of the membrane.
  • the channels of the membrane can comprise one or more ridges.
  • the ridges can comprise a horizontal and vertical section relative to the flat surface of the membrane.
  • the membrane comprises one or more ridges or grooves between ridges of adjacent channels.
  • the angle between horizontal and vertical sections of the channels is from 185° to 355°, 210° to 350°, 210° to 340°, 210° to 330°, 220° to 320°, 240° to 300°, 250° to 290° or 260° to 280°.
  • the scaffold membrane topography comprises channels, grooves, post, holes, hexagons and/or stars.
  • the angle of the star is 20, 36, 60, 108 or 120 degrees.
  • the scaffold membrane topography comprises a combination of channels, grooves, post, holes, hexagons and/or stars.
  • Membranes can be fabricated using known methods, as detailed in Tejeda-Montes et al., 2012.
  • a scaffold membrane is incubated with a mineralizing solution of the invention.
  • the step of incubating comprises nucleation followed by crystal growth.
  • homogenous nucleation mineralization occurs in a bulk solution, does not require a substrate or template, and exhibits a spherical nucleus in order to overcome the free energy barrier.
  • heterogeneous nucleation originates from impurities in the system (i.e. surfaces and matrices) and requires less energy than homogeneous nucleation because the surface energy barrier is lowered by the interfacial energy following the Gibbs free energy equations (Wang, L. & Nancollas, G. H. Calcium orthophosphates: Crystallization and Dissolution. Chemical Reviews 108, 4628-4669 (2008)).
  • ⁇ ⁇ ⁇ G homogenous ( 4 3 ⁇ ⁇ ⁇ ⁇ r 3 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ + 4 ⁇ ⁇ ⁇ ⁇ r 2 ⁇ ⁇ ) ( 1 )
  • ⁇ ⁇ ⁇ G heterogenous ⁇ ⁇ ⁇ G homogenous * ⁇ ⁇ ( 2 )
  • ⁇ G is the free energy barrier of nucleation
  • r is the radius of the nucleus
  • ⁇ is the density of the new phase
  • ⁇ is the difference in chemical potential between the new phase and the existing phase (also known as supersaturation)
  • ⁇ is the surface tension between the nucleus and bulk solution
  • ⁇ is the contact angle between the bulk solution and the substrate in the case of heterogeneous nucleation.
  • methods of the invention comprise heterogeneous nucleation due to the presence of a scaffold membrane. Heterogeneous nucleation gives more control over the nucleation rate, and the crystal orientation, polymorphism, and morphology are influenced by the type of crystal growth mechanism.
  • the membrane can be any membrane as described herein.
  • the membrane is from a material with high mineralizing properties.
  • the membrane is formed of natural elastin.
  • the elastin comprises the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • the membrane is formed of collagen, amelogenin, Elastin-like protein membrane or Elastin-like protein hydrogel.
  • the Elastin-like protein membrane or Elastin-like protein hydrogel can comprise the tropoelastin recurrent motif Val-Pro-Gly-X-Gly (VPGXG), where X is any amino acid apart from proline.
  • the term “hierarchically ordered” refers to the hierarchal ordering of different structures at different length scales. Materials such as bone and enamel have multiple levels of hierarchical structure. The present inventors have, for the first time, generated a synthetic enamel with a hierarchal structure that is similar to natural enamel.
  • the synthetic crystals of the invention comprise an assembly of hierarchically ordered crystallographic, nanostructures, microstructures and macrostructures, as discussed below.
  • the synthetic crystalline structures comprise nanostructures, microstructures and macrostructures assembled in an hierarchal order across multiple length-scales.
  • the length-scales can be crystallographic, nanometre, micrometre, one hundred micrometre and millimetre.
  • the synthetic crystalline structures comprises three levels, preferably at least four levels of hierarchy.
  • the four levels of hierarchy are nanometre, micrometre, one hundred micrometre and millimetre.
  • the five levels of hierarchy are crystallographic, nanometre, micrometre, one hundred micrometre and millimetre.
  • Each level of hierarchy comprises morphologically distinct structures.
  • the hierarchical structure of the synthetic enamel mirrors that found in natural dental enamel. Therefore, the synthetic crystals of the invention have a morphology that approaches or is identical to naturally occurring biological dental enamel.
  • the material is apatite, with a space group, unit cell size, and structural parameters matching apatite values, as reported in the literature (Young, R. A. & Elliott, J. C. Atomic-scale bases for several properties of apatites. Archives of Oral Biology 11, 699-707 (1966)).
  • the structures of the invention exhibit elongated needle shaped nanocrystals or elongated plate-like shaped nanocrystals.
  • the nanocrystals are up to about 200 nm. In one embodiment the nanocrystals are up to about 120 nm. In one embodiment the nanocrystals are up to about 110 nm. In one embodiment the nanocrystals are up to about 100 nm. In one embodiment the needle shaped nanocrystals are about 10 nm to about 200 nm in width. In one embodiment the needle shaped nanocrystals are about 60 to about 110 nm in width. In one embodiment the needle shaped nanocrystals are about 70 to about 100 nm in width.
  • the needle shaped nanocrystals are about 25 to about 120 nm in width, optionally about 85 nm in width. Fluroapatite crystals, in particular, may exhibit such a morphology.
  • the synthetic crystal is fluorapatite and the nanocrystals are elongated needle shaped nanocrystals.
  • the plate-like crystals are considered to be plate-like, for example on the basis of their chemistry. Using the microscope to observe the side of the plate-like crystals, it is possible to measure the thickness of the plate-like crystal.
  • the plate-like shaped nanocrystals are at least 1 nm in thickness, optionally up to about 50 nm in thickness.
  • the plate-like nanocrystals are from about 1 nm to about 40 nm thick.
  • the plate-like shaped nanocrystals are from about 1 nm to about 40 nm thick.
  • the needle shaped nanocrystals are from about 15 to about 25 nm thick.
  • the plate-like shaped nanocrystals are from about 16 to about 17 nm thick. In one embodiment the plate-like shaped nanocrystals are from about 17 nm thick. In one embodiment, the synthetic crystal is hydroxyapatite and the nanocrystals are plate-like nanocrystals. In one embodiment, the synthetic crystal is hydroxyapatite and the nanocrystals are plate-like nanocrystals that are from about 1 nm to about 40 nm thick. In one embodiment, the synthetic crystal is hydroxyapatite and the nanocrystals are from about 15 to about 25 nm thick.
  • the synthetic crystal is hydroxyapatite and the nanocrystals are plate-like nanocrystals that are from about 16 to about 17 nm across the plate.
  • the nanocrystals are organized into about 4 ⁇ m thick prism-shaped microstructures, resembling the prism microstructures observed in natural enamel.
  • a prism is a solid geometric figure whose two ends are similar, equal, and parallel rectilinear figures, and whose sides are parallelograms. The term prism is interchangeable with fingers or micro-rods.
  • the nanocrystals are form about 1 to about 90 ⁇ m, from about 1 to about 0 ⁇ m, from about 1 to about 70 ⁇ m, from about 1 to about 60 ⁇ m, from about 1 to about 50 ⁇ m, from about 1 to about 40 ⁇ m, from about 1 to about 30 ⁇ m, from about 1 to about 20 ⁇ m, from about 1 to about 10 ⁇ m, or from about 1 to about 5 ⁇ m thick prism-shaped microstructures.
  • the nanocrystals form prism-shaped microstructures having a thickness of about 4 ⁇ m.
  • the prism-shaped microstructures are aligned or substantially aligned with one another and/or are adjacent or substantially adjacent to one another. In one embodiment, the prism-shaped microstructures recur along the enamel-like microstructures. In one embodiment, the prism-shaped microstructures recur at approximately 1 ⁇ m intervals, for example they recur at from 0.1 to 10 ⁇ m intervals, or at from 0.5 to 5 ⁇ m intervals.
  • the nanocrystals are organized into circular concentric ring microstructures.
  • the microstructures assemble to form circular structures or asymmetrical structures hundreds of microns in diameter that come together to fill macroscopic areas (i.e the microstructures assemble to form macrostructures).
  • An asymmetrical structure can be oval, elongated in shape, non-circular, substantially circular shaped or other non-symmetrical shape.
  • the microstructures of the synthetic crystal assemble to form a circular structure.
  • the microstructures of the synthetic crystal assemble to form an asymmetrical structure.
  • the synthetic fluorapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five)level hierarchy comprises needle-shaped nanocrystals that are organized into prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic fluorapatite crystalline structure comprises a four (or five)level hierarchy wherein the four (or five) level hierarchy comprises needle-shaped nanocrystals that are organized into prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals that are organized into prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four(or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals that are organized into prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic fluorapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises needle-shaped nanocrystals about 10 nm to about 200 nm in width, optionally about 85 nm in width, that are organized into about 1 to about 90 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic fluorapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises needle-shaped nanocrystals about 10 nm to about 200 nm in width, optionally about 85 nm in width, that are organized into about 1 to about 90 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals about 1 nm to about 40 nm thick, optionally about 17 nm thick, that are organized into about 1 to about 90 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals about 1 nm to about 40 nm thick, optionally about 17 nm thick, that are organized into about 1 to about 90 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic fluorapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises needle-shaped nanocrystals about 25 to about 120 nm in width, optionally about 85 nm in width, that are organized into about 1 to about 5 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic fluorapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises needle-shaped nanocrystals about 25 to about 120 nm in width, optionally about 85 nm in width, that are organized into about 1 to about 5 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals about 1 to about 40 nm thick, optionally about 17 nm thick, that are organized into about 1 to about 5 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise circular structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic hydroxyapatite crystalline structure comprises a four (or five) level hierarchy wherein the four (or five) level hierarchy comprises plate-like shaped nanocrystals about 1 to about 40 nm thick, optionally about 17 nm thick, that are organized into about 1 to about 5 ⁇ m thick prism-like microstructures, and the prism-like microstructures comprise asymmetrical structures hundreds of microns in diameter and can fill macroscopic areas.
  • the synthetic crystals of the invention can beneficially be used to enhance or promote desired cell characteristics. A number of benefits can be achieved at the site of implantation or administration.
  • the synthetic crystals of the invention increase cell adhesion.
  • the synthetic crystals of the invention increase or promote cell growth.
  • the synthetic crystals of the invention increase or promote cell migration.
  • the synthetic crystals of the invention increase or promote cell viability. Cell viability is the cells ability to survive and/or live successfully.
  • the synthetic crystals of the invention increase or promote tissue regeneration.
  • the cell is selected from the group consisting of stem cells, odontoblasts, dental stem cells, osteoclasts and osteoblasts.
  • the synthetic crystals of the invention are acid-resistant. In one embodiment, the synthetic crystals of the invention are resistant to acid attack. Acid attack is the exposure of an object to acid (i.e. having a pH less than 7).
  • the synthetic crystals of the invention include those obtained or obtainable by the methods and processes of the present invention.
  • a process for producing hierarchically ordered mineralized structure comprises the step of contacting a protein-scaffold membrane with a mineralizing solution.
  • the mineralizing solution is a supersaturated solution of Ca 2+ and PO 4 3 ⁇ .
  • the mineralizing solution is a supersaturated solution of Ca 2+ , PO 4 3 ⁇ , and F.
  • the contacting step is performed at physiological pH and temperature.
  • the step of contacting comprises the terms submerging and/or incubating the scaffold membrane in the mineralizing solution.
  • the process of the invention comprises the step of contacting a protein-scaffold membrane with a mineralizing solution.
  • the ELP membrane or hydrogel can be cross-linked.
  • the ELP membrane or hydrogel can be cross-linked by chemical cross-linking, enzymatic cross-linking by tissue transglutaminase, photoinitiated and/or ⁇ -irradation cross-linking.
  • the ELP membrane or hydrogel has a cross linker ratio of greater than about 0.25.
  • the ELP membrane or hydrogel has a cross linker ratio of between about 0.25 to 24.
  • the ELP membrane or hydrogel has a cross linker ratio of between about 0.25 to 20.
  • the ELP membrane or hydrogel has a cross linker ratio of about 0.5 to about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of about 6 to 12. In one embodiment, the ELP membrane or hydrogel has a cross linker ratio of about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of greater than about 0.25. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of between about 0.25 to 24. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of between about 0.25 to 20.
  • the ELP membrane or hydrogel has a cross linker to lysine ratio of about 0.5 to about 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of about 6 to 12. In one embodiment, the ELP membrane or hydrogel has a cross linker to lysine ratio of about 12.
  • the cross-linker ratio is the ratio of the molar concentration of cross-linker to the molar concentration of amine or carboxylic groups of the ELP membrane or hydrogel, protein, polymer, peptide or amino acid. In one embodiment the cross-linker is hexamethyl diisocyanate.
  • the step of cross-linking can occur in vivo.
  • the cross-linking solution can be added to the in vivo location, for example to the tooth or bone of a patient.
  • the process of the invention comprises the step of contacting a protein-scaffold membrane with a mineralizing solution. Altering the ionic content of the mineralizing solution changes the chemistry of the resulting apatite. Generally, the mineralizing solution is aqueous.
  • the mineralizing solution comprises calcium. In one embodiment, the mineralizing solution contains from about 0.1 mM to about 1M Ca 2+ . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 800 mM Ca 2+ . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 600 mM Ca 2+ . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 400 mM Ca 2+ . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 200 mM Ca 2+ . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 100 mM Ca 2+ .
  • the mineralizing solution contains about 0.5 to about 10 mM Ca 2+ . In one embodiment, the supersaturated solution comprises about 9 to about 11 mM Ca 2+. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM Ca 2+.
  • the supersaturated solution contains from about 0.1 mM to about 1M PO 4 3 . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 800 mM PO 4 3 . In one embodiment, the supersaturated solution contains about from 0.1 mM to about 600 mM PO 4 3 . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 400 mM PO 4 3 . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 200 mM PO 4 3. . In one embodiment, the supersaturated solution contains from about 0.1 mM to about 100 mM PO 4 3. .
  • the supersaturated solution contains from about 1 mM to about 10 mM PO 4 3. . In one embodiment, the supersaturated solution contains from about 4 to about 8 mM PO 4 3. . In one embodiment, the supersaturated solution contains from about 5 to about 7 mM PO 4 3 ⁇ . In one embodiment, the supersaturated solution contains from about 5.5 to about 6.5mM PO 4 3 ⁇ . In a preferred embodiment the ration of calcium to phosphate is about 1.67 mM. In this embodiment the resulting crystalline structure is apatite.
  • the mineralizing solution comprises from about 0.01 mM to about 1M F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.01 mM to about 800 mM F ⁇ . In one embodiment, the mineralizing solution comprises a from bout 0.01 mM to about 600 mM F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.01 mM to about 400 mM F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.01 mM to about 200 mM F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.01 mM to about 100 mM F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.01 mM to about 50 mM F ⁇ .
  • the mineralizing solution comprises from about 0.1 mM to about 5 mM F ⁇ . In one embodiment, the mineralizing solution comprises from about 0.1 to about 4 mM F ⁇ . In one embodiment, the supersaturated solution comprises from about 1 to about 3 mM F ⁇ . In one embodiment, the supersaturated solution comprises from about 1.5 to about 2.5 mM F ⁇ . In another embodiment the mineralizing solution does not comprise F ⁇ . In such an embodiment, the resulting crystalline structure is hydroxyapatite.
  • the mineralizing solution comprises strontium. In one embodiment, the mineralizing solution contains from about 0.5 to about 10 mM strontium. In one embodiment, the supersaturated solution comprises from about 9 to about 11 mM strontium. In a preferred embodiment, the supersaturated solution comprises from about 2.5 to about 10 mM strontium.
  • the mineralizing solution comprises zinc. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM zinc. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM zinc. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM zinc.
  • the mineralizing solution comprises silver. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM silver. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM silver. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM silver.
  • the mineralizing solution comprises barium. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM barium. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM barium. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM barium.
  • the mineralizing solution comprises carbonate. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM carbonate. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM carbonate. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM carbonate.
  • the mineralizing solution comprises magnesium. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM magnesium. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM magnesium. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM magnesium.
  • the mineralizing solution comprises potassium. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM potassium. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM potassium. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM potassium.
  • the mineralizing solution comprises iron. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM iron. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM iron. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM iron.
  • the mineralizing solution comprises lead. In one embodiment, the mineralizing solution contains about 0.5 to about 10 mM lead. In one embodiment, the supersaturated solution comprises about 9 to about 11 mM lead. In a preferred embodiment, the supersaturated solution comprises about 2.5 to about 10 mM lead.
  • the supersaturated solution comprises about 8 to about 12 mM Ca 2+ , about 4 to about 8 mM PO 4 3 , optionally further comprising about 0.1 to about 4 mM F ⁇ .
  • the supersaturated solution comprises about 10 mM Ca 2+ , and about 6 mM PO 4 3 ⁇ , optionally further comprising about 2 mM F ⁇ .
  • the mineralizing is solution is a bodily fluid.
  • the bodily fluid is saliva, blood, interstitial fluid, serum or plasma.
  • the step of contacting an elastin-like polypeptide membrane or hydrogel with a solution of calcium and phosphate ions is an in vivo step.
  • the in vivo step occurs in a mouth, on a bone or on a human tissue.
  • the protein-scaffold membrane is contacted with solution, in particular a supersaturated solution, having a specific pH value.
  • the pH is from about 2 to about 11.
  • the pH is from about 3 to about 8.
  • the pH is from 4 to 8.
  • the pH is from about 4 to about 7.
  • the pH is from about 5 to about 7.
  • the pH is about 6.
  • the protein-scaffold membrane is contacted with a supersaturated solution at physiological pH.
  • physiological pH is from about 2 to about 11.
  • pH is from about 3 to 9.
  • pH is from about 4 to 8.
  • the pH is from about 5 to 8.
  • the pH is from about 6 to 7.
  • the pH is 7.4.
  • the supersaturated solution comprises about 8 to about 12 mM Ca 2+ and about 4 to about 8 mM PO 4 3 , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 5 to about 7.
  • the supersaturated solution comprises about 10 mM Ca 2+ and about 6 mM PO 4 3 , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6.
  • the supersaturated solution comprises about 8 to about 12 mM Ca 2+ , about 4 to about 8 mM PO 4 3 and about 0.1 to about 4 mM F ⁇ , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6 to about 7.
  • the supersaturated solution comprises about 10 mM Ca 2+ , about 6 mM PO 4 3 ⁇ and about 2 mM F ⁇ , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6.
  • two solutions having different pH values can be used.
  • two different solutions having different pH values can be used. Reducing the pH during mineralization of the ELP membrane can control the size of the hierarchically-ordered crystalline structures.
  • the hierarchically-ordered crystalline structures are up to 70 ⁇ m in height and 350 ⁇ m in diameter when the starting pH of the solution is set to 6.0 and drops to 3.7 during mineralization.
  • the protein-scaffold membrane is contacted with a supersaturated solution at a first pH and then contacted at a second, lower pH.
  • the first pH is about 5.5 to about 6.5.
  • the second lower pH is about 3.0 to about 4.0.
  • the first pH is about 5.5 to about 6.5 and the second lower pH is about 3.0 to about 4.0.
  • the first pH is about 6.0 and the second lower pH is about 3.7.
  • the ELP membrane is contacted with a supersaturated solution at a first pH and then contacted at a second lower pH.
  • the first pH is about 5.5 to about 6.5.
  • the second, lower pH is 3.0 to 4.0.
  • the first pH is about 5.5 to about 6.5 and the second lower pH is about 3.0 to about 4.0.
  • the first pH is about 6.0 and the second lower pH is about 3.7.
  • Much larger structures can be grown with diameters up to 1 mm when the pH is controlled throughout the mineralization process, for example using BIS-TRIS buffer, in particular where the pH drops from 6.0 to 5.7.
  • the protein-scaffold membrane is contacted with a supersaturated solution at a first pH and then contacted with a second lower pH.
  • the first pH is about 5.5 to about 6.5.
  • the second lower pH is about 3.0 to about 5.7.
  • the second lower pH is about 3.0 to about 4.0.
  • the first pH is about 5.5 to about 6.5 and the second lower pH is about 3.0 to about 4.0.
  • the first pH is about 6.0 and the second lower pH is about 5.7.
  • the ELP membrane or hydrogel is contacted with a supersaturated solution at a first pH and then contacted with a second lower pH.
  • the first pH is about 5.5 to about 6.5.
  • the second lower pH is about 3.0 to about 5.7. In one embodiment the second lower pH is about 3.0 to about 4.0. In a preferred embodiment the first pH is about 5.5 to about 6.5 and the second lower pH is about 3.0 to about 4.0. In a preferred embodiment the first pH is about 6.0 and the second lower pH is about 5.7.
  • the method may comprise a step of washing the membrane before contacting the membrane with the second pH.
  • the pH may be adjusted in situ.
  • the time spent at each pH can vary according to requirements.
  • the scaffold membrane will be incubated for at least 8 hours, at least 10 hours, at least 1 day, at least 4 days and more preferably at least 7 days at each pH.
  • the scaffold membrane is incubated for at least 8 hours in each pH solution.
  • the protein-scaffold membrane is contacted with a supersaturated solution at a temperature of from about 15° C. to about 90° C.
  • the temperature is from about 30° C. to about 60° C.
  • the temperature is from about 35° C. to about 55° C.
  • the temperature is from about 36.5° C. to about 37.5° C., in particular about 37° C.
  • the ELP membrane or hydrogel is contacted with a supersaturated solution at a temperature of from about 15° C. to about 90° C.
  • the temperature is from about 30° C. to about 60° C.
  • the temperature is from about 35° C. to about 55° C.
  • the temperature is from about 36.5° C. to about 37.5° C., in particular about 37° C.
  • the ELP membrane or hydrogel is contacted with a supersaturated solution at or above the inverse transition temperature of the ELP membrane.
  • An ELP membrane will transition to an organised, hierarchal crystal structure comprising ⁇ -spiral conformations above the inverse transition temperature.
  • the skilled person would understand that the inverse transition temperature will vary dependent on the type of membrane or hydrogel.
  • the ELP membrane or hydrogel has a ⁇ -spiral conformation when hierarchical mineralization takes place above the inverse transition temperature. The presence of a ⁇ -spiral conformation can be confirmed using circular dichroism (CD) spectroscopy.
  • CD circular dichroism
  • the inverse transition temperature of the ELP membrane is about 10° C. to 80° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 33° C. to 41° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 35° C. to 39° C. In one embodiment, the inverse transition temperature of the ELP membrane is about 37° C.
  • the supersaturated solution comprises about 8 to about 12 mM Ca 2+ and about 4 to about 8 mM PO 4 3
  • the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 5 to about 7 and at a temperature of about 36.5° C. to about 37.5° C.
  • the supersaturated solution comprises about 10 mM Ca 2+ and about 6 mM PO 4 3 ⁇
  • the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6 and at a temperature of about 36.5° C. to about 37.5° C.
  • the supersaturated solution comprises about 8 to about 12 mM Ca 2+ , about 4 to about 8 mM PO 4 3 ⁇ and about 0.1 to about 4 mM F ⁇ , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6 to about 7 and at a temperature of about 36.5° C. to about 37.5° C.
  • the supersaturated solution comprises about 10 mM Ca 2+ , about 6 mM PO 4 3 ⁇ and about 2 mM F ⁇ , and the protein-scaffold membrane is contacted with a supersaturated solution having a pH value of about 6 and at a temperature of about 36.5° C. to about 37.5° C.
  • the protein-scaffold membrane is contacted with a supersaturated solution for about 8 to about 12 hours. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for about 10 hours. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 10 hours. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for about 1 to about 20 days. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for about 5 to about 15 days. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for about 5 to about 10 days.
  • the protein-scaffold membrane is contacted with a supersaturated solution for about 7 to about 9 days. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 1 day. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 5 days. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 6 days. In one embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 7 days. In a preferred embodiment the protein-scaffold membrane is contacted with a supersaturated solution for at least about 8 days.
  • the ELP membrane or hydrogel is contacted with a supersaturated solution for about 1 to about 20 days. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for about 5 to about 15 days. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for about 5 to about 10 days. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for about 7 to about 9 days. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for at least about 1 day. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for at least about 5 days.
  • the ELP membrane or hydrogel is contacted with a supersaturated solution for at least about 6 days. In one embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for at least about 7 days. In a preferred embodiment the ELP membrane or hydrogel is contacted with a supersaturated solution for at least about 8 days.
  • the ELP membrane or solution is formed by dissolving an ELP in solvent.
  • the ELP concentration in solvent is from about 1 to about 20% by weight, more particularly from about 1 to about 15% by weight, preferably at least 1% or at least 2%, or at least 3%, or at least 4%, or at least 5% by weight.
  • the pH is changed during the step of contacting the ELP membrane or hydrogel with a supersaturated solution.
  • a supersaturated solution using published methods, for example, Chen, H. et al. Synthesis of Fluorapatite Nanorods and Nanowires by Direct Precipitation from Solution. Cryst Growth Des 6, 1504-1508, doi:10.1021/cg0600086 (2006).
  • the solution of the invention is supersaturated.
  • the methods of the invention are performed in vitro.
  • the synthetic crystals of the invention can be used as dental restorative materials, dental enamel, metallic implants, cements, and ceramics. In one aspect of the invention, the synthetic crystals of the invention can be used in conjunction with dental restorative materials, dental enamel, metallic implants, cements, and ceramics. There is therefore provided dental implants comprising the synthetic crystal of the invention.
  • a method for growing a hierarchical crystalline structure on a dental implant comprises contacting a dental implant comprising a protein-scaffold membrane with a mineralizing solution of the invention.
  • protein-scaffold membrane is an ELP membrane or an ELP hydrogel.
  • the crystalline structure is apatite.
  • the crystalline structure is fluroapatite.
  • the crystalline structure is hydroxyapatite.
  • the synthetic crystal is used in a method of coating a medical implant or dental implant.
  • the surface may be partially or fully covered with the synthetic crystal.
  • the coating can be chemically bonded to the implant surface.
  • the synthetic crystals of the invention can be used as a medical implant, synthetic graft, coating, prosthesis, orthosis, paste, malleable putty or film.
  • the synthetic crystals of the invention can be used in conjunction with medical implant, synthetic graft, coating, prosthesis, orthosis, paste, malleable putty or film.
  • a method for growing a hierarchical crystalline structure on a medical implant, synthetic graft, prosthesis, orthosis, paste, malleable putty or film.
  • the method comprises contacting a medical implant, synthetic graft, prosthesis, orthosis, paste, malleable putty or film comprising a protein-scaffold membrane with a mineralizing solution of the invention.
  • protein-scaffold membrane is an ELP membrane or an ELP hydrogel.
  • the crystalline structure is apatite.
  • the crystalline structure is fluroapatite.
  • the crystalline structure is hydroxyapatite.
  • the synthetic crystal is used in a method of coating a medical device, medical implant, synthetic graft, prosthesis or orthosis.
  • the surface may be partially or fully covered with the synthetic crystal.
  • the coating can be chemically bonded to the implant surface.
  • the synthetic crystals of the invention have numerous advantages properties for a wide variety of uses.
  • the acid-resistance property of the synthetic crystals allows them to be used as a protective coating for a number of surfaces.
  • a coating comprising synthetic crystals of the invention is provided.
  • a acid-resistant coating comprising synthetic crystals of the invention is provided.
  • a coating comprising synthetic crystals of the invention for use with protective clothing and equipment, military equipment and clothing is provided.
  • the synthetic crystal or dental implant of the invention may be provided for use in the prevention and/or treatment of dental disease.
  • the dental disease may be dental caries, dental erosion, alveolar bone erosion, periodontitis, peri-implantitis or dental pulp disease.
  • the synthetic crystal of the invention may be administered in combination with one or more pharmaceutically active agents.
  • the dental disease may be dental caries, dental erosion, alveolar bone erosion, periodontitis, peri-implantitis or dental pulp disease.
  • the invention may be seen as providing the use of a synthetic crystal or dental implant of the invention in the preparation of a medicament or dental implant for the treatment and/or prevention of dental disease.
  • the dental disease may be dental caries, dental erosion, alveolar bone erosion, periodontitis, peri-implantitis or dental pulp disease.
  • the synthetic crystal of the invention may be provided for use in the prevention and/or treatment of dental hypersensitivity.
  • synthetic crystal may be administered in combination with one or more pharmaceutically active agents.
  • This aspect of the invention therefore also extends to a method of treatment of or prevention of dental hypersensitivity in a subject, comprising administration to the subject a synthetic crystal of the invention.
  • the invention may be seen as providing the use of a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention of dental hypersensitivity.
  • the synthetic crystal of the invention may be provided for use in the prevention and/or treatment of demineralisation of teeth.
  • Demineralisation of teeth may be defined as a loss of hydroxyapatite from the teeth.
  • synthetic crystal may be administered in combination with one or more pharmaceutically active agents. Preparation and formulation of such compositions would be known by the skilled person.
  • This aspect of the invention therefore also extends to a method of treatment of or prevention of demineralisation of teeth, comprising administration to the subject a synthetic crystal of the invention.
  • the invention may be seen as providing the use of a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention of demineralisation of teeth.
  • the synthetic crystals of the present invention may be employed alone or in conjunction with other compounds, such as therapeutic compounds, e.g. anti-inflammatory drugs, cytotoxic agents, cytostatic agents or antibiotics.
  • therapeutic compounds e.g. anti-inflammatory drugs, cytotoxic agents, cytostatic agents or antibiotics.
  • the synthetic crystal of the invention may be provided for use in the prevention and/or treatment of bone demineralisation, low bone density or osteoporosis.
  • the use of the crystal structures of the invention for increasing bone density is interchangeable with low bone mass and osteopenia.
  • Low bone density can be considered as bone density that is below the average bone density of a health human.
  • Low bone density can be defined as a T-score of below ⁇ 1.0 when using the central dual energy x-ray absorptiometry (DXA or DEXA) bone density test.
  • BMD bone mineral density
  • PBM peak bone mass
  • a T-score of below ⁇ 2.5 when using the central dual energy x-ray absorptiometry (DXA or DEXA) bone density test is defined as osteoporosis.
  • Bone demineralization is the loss, decrease or removal of the mineral constituents of bone.
  • This aspect of the invention therefore also extends to a method of treatment of or prevention of bone demineralisation, low bone density or osteoporosis in a subject, comprising administration to, or implantation into, the subject a synthetic crystal of the invention.
  • a method of increasing bone density is provided
  • the invention may be seen as providing the use of a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention of bone demineralisation, low bone density or osteoporosis.
  • the synthetic crystal of the invention may be provided for use in the prevention and/or treatment of bone disease.
  • the bone disease is osteoporosis, osteoarthritis, osteosclerosis, osteogenesis imperfecta, Paget's disease of bone, metabolic bone disease, osteomalacia, osteopenia, arthritis or sarcoma.
  • synthetic crystal may be administered in combination with one or more pharmaceutically active agents.
  • This aspect of the invention therefore also extends to a method of treatment of or prevention of bone disease in a subject, comprising administration to the subject a synthetic crystal of the invention.
  • the bone disease is osteoporosis, osteoarthritis, osteosclerosis, osteogenesis imperfecta, Paget's disease of bone, metabolic bone disease, osteomalacia, osteopenia, arthritis or sarcoma.
  • the invention may be seen as providing the use of a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention bone disease.
  • the bone disease is osteoporosis, osteoarthritis, osteosclerosis, osteogenesis imperfecta, Paget's disease of bone, metabolic bone disease, osteomalacia, osteopenia, arthritis or sarcoma.
  • the synthetic crystal of the invention may be provided for use in the prevention and/or treatment of a bone defect.
  • the bone defect is a bone fracture, bone fracture associated with trauma, bone injury, bone cavity or bone lesion.
  • the synthetic crystals of the invention may be useful in treating bone defects associated with the interface of bone with connective tissues such as cartilage, ligaments and tendons.
  • the bone defect is damage to the bone-cartilage interface, bone-ligament interface or a bone-tendon interface.
  • synthetic crystal may be administered in combination with one or more pharmaceutically active agents. Preparation and formulation of such compositions would be known by the skilled person.
  • the bone defect is a bone fracture, bone fracture associated with trauma, bone injury, bone cavity or bone lesion.
  • the bone defect is damage to the bone-cartilage interface, bone-ligament interface or a bone-tendon interface.
  • the invention may be seen as providing the use of a synthetic crystal of the invention in the preparation of a medicament for the treatment and/or prevention of bone defect.
  • the bone defect is a bone fracture, bone fracture associated with trauma, bone injury, bone cavity or bone lesion.
  • the bone defect is damage to the bone-cartilage interface, bone-ligament interface or a bone-tendon interface.
  • the synthetic crystals of the present invention may be employed alone or in conjunction with other compounds, such as therapeutic compounds, e.g. anti-inflammatory drugs, cytotoxic agents, cytostatic agents or antibiotics.
  • therapeutic compounds e.g. anti-inflammatory drugs, cytotoxic agents, cytostatic agents or antibiotics.
  • a method comprising contacting an elastin-like polypeptide membrane or hydrogel with a solution of calcium and phosphate ions in vivo.
  • the solution may further comprises fluoride ions, and or other components as described herein.
  • the concentrations of the various ions are discussed elsewhere, and apply equally to this aspect of the invention.
  • the method comprises the step of administered the membrane or hydrogel to a patient, in particular the surface of a patient, such as a tooth or bone. After contact the membrane or hydrogel with the solution, the ELP membrane or hydrogel and the ions form a synthetic crystal having a hierarchical structure formed on the membrane or hydrogel scaffold. In this way, the crystal structures of the invention can be formed in vivo.
  • the solution comprising the ions may be an exogenous solution.
  • the method may further comprise the step of administering the exogenous solution before, concurrently or after administration of the membrane or hydrogel.
  • the solution of ions is an endogenous solution.
  • Such an endogenous solution may be a bodily fluid, for example saliva, interstitial fluid, blood or plasma.
  • the method further comprises the step of cross-linking in vivo.
  • the cross linker may be added after the membrane or hydrogel is added to the solution (and after the mineralising solution is added, if an exogenous solution is being used).
  • the method is a method of treatment and/or prevention.
  • Forming the crystal structures in vivo allows the formation of the crystals directly at the site of application, i.e. the site where the biomimetic structures are required.
  • the method may be a method of treatment and/or prevention of a dental disease or bone disease or a bone defect.
  • the dental disease may be demineralisation of teeth or dental hypersensitivity.
  • the bone disease may be low bone density or osteoporosis, bone disease.
  • the present invention is also useful in increasing bone density and tooth enamel density.
  • the term “treatment” includes any regime that can benefit a human or a non-human animal.
  • the treatment of “non-human animals” extends to the treatment of domestic animals, including horses and companion animals (e.g. cats and dogs) and farm/agricultural animals including members of the ovine, caprine, porcine, bovine and equine families.
  • the treatment of “non-human” animals extends to the treatment of any animal with teeth.
  • the treatment may be in respect of any existing condition or disorder, or may be prophylactic (preventive treatment).
  • the treatment may be of an inherited or an acquired disease.
  • the treatment may be of an acute or chronic condition.
  • the treatment is of a condition/disorder associated with inflammation.
  • the present invention may also find application in veterinary medicine for treatment/prophylaxis of domestic animals including horses and companion animals (e.g. cats and dogs) and farm animals which may include members of the ovine, porcine, caprine, bovine and equine families.
  • horses and companion animals e.g. cats and dogs
  • farm animals which may include members of the ovine, porcine, caprine, bovine and equine families.
  • a pharmaceutical composition comprising a synthetic crystal of the invention.
  • the pharmaceutical composition may be formulated for oral administration or for topical administration in the mouth cavity or on the teeth or gums by way of a coating.
  • the pharmaceutical composition may be an artificial saliva, a mouth wash (buccal wash), tooth paste or cream, moisturiser, chewing gum, drink or other oral healthcare preparation.
  • compositions in accordance with this aspect of the invention may comprise other pharmaceutically active substances, such as anti-bacterial, anti-viral, anti-fungal, analgesic substances.
  • the composition may also comprise pharmacologically acceptable salts such as fluoride salts or phosphate salts, for example a fluoride salt or a phosphate with an alkali metal or an alkaline earth metal, e.g. sodium fluoride (NaF).
  • the pharmaceutical composition may be formulated using any convenient adjuvant and/or physiologically acceptable diluents.
  • compositions such as sorbitol, xanthan gum, guar gum, and/or cellulose derivatives such as hydroxypropylmethylcellulose (HPMC), sodium carboxymethyl cellulose etc.
  • HPMC hydroxypropylmethylcellulose
  • a kit comprising an ELP membrane or hydrogel of the invention and a mineralising solution of the invention.
  • the mineralising solution can be contacted with the ELP membrane or hydrogel of the invention in vivo.
  • the mineralising solution may be as described above.
  • a kit is provided comprising an ELP membrane or hydrogel of the invention, a mineralising solution of the invention and a therapeutically active agent.
  • a kit is provided comprising a synthetic crystal of the invention or a pharmaceutical composition comprising the synthetic crystal of the invention and a therapeutically active agent.
  • the kit further comprises a cross-linker. Details of the possible cross-linkers that may be included are discussed above.
  • the kit further comprises instructions for use.
  • a major goal in materials science is to develop bioinspired functional materials that can offer precise control of molecular building-blocks across multiple length-scales.
  • the present inventors have discovered they can grow hierarchically-ordered crystal structures, in particular apatite structures, that resemble those found in human dental enamel to a level previously unreported.
  • the structures exhibit elongated needle-like fluorapatite nanocrystals of about 85 nm thick that are organized into approximately 4 ⁇ m thick prism-like microstructures, which assemble to form circular structures hundreds of microns in diameter that come together to fill macroscopic areas.
  • the method comprises the step of contacting an ELP membrane with a solution of calcium, phosphate and fluoride mineralizing ions wherein the contacting step is performed at about pH 6 to 7 and about 35° C. to 40° C.
  • Membranes were fabricated using a recently published method, and as detailed further below (Tejeda-Montes, E. et al. Engineering membrane scaffolds with both physical and biomolecular signaling. Acta Biomaterialia 8, 998-1009 (2012)) and with systematic processing variations in order to control, where different ELP molecules as shown in Table 2 were dissolved in anhydrous dimethylformamide (DMF) at room temperature in a low-humidity conditions (less than 20%) inside a polymer glove box.
  • DMF dimethylformamide
  • the general process of membrane fabrication is a drop-casting technique that includes four steps:
  • the ELPs were dissolved in anhydrous dimethylformamide (Sigma-Aldrich, Germany) at room temperature at a concentration of 5% (50 mg/ml).
  • the ELP solution was then mixed with hexamethyl diisocyanate (HDI) (Sigma-Aldrich, Germany) at a ratio of available lysine side chains to HDI molecules of 2:3, thus providing an excess of cross-linker.
  • the crosslinker ratio can be varied from 1:0.25, 1:0.5, 1:1, 1:3, 1:6, 1:12, 1:24.
  • the cross-linking reaction was left to proceed under a nitrogen atmosphere using a polymer glovebox (Cleaver Scientific, Wolf Laboratories Ltd., UK).
  • Different volumes of the cross-linked polymer solution were added to the surface of pieces of polydimethylsiloxane (PDMS) (Sylgard 184, Dow Corning, USA) or bare or photopatterned resist on a (1 1 1)-oriented silicon wafer (Siltronix, France).
  • PDMS polydimethylsiloxane
  • the solution was allowed to air-dry on top of the substrates either statically or while spinning constantly on a spin-coater (Ws-650Sz, Laurell Technologies, USA) to allow solvent evaporation, ELP assembly, and a precise and reproducible membrane thickness. Finally, the membrane was released from the substrate.
  • the membranes were washed over a period of 7 days with various substances. First, they were placed in a Buchner funnel, where 20 ml of 100% dimethylsulfoxide (DMSO) was added drop-wise to the top of each membrane, which caused them to swell considerably. They were then left overnight immersed in 10% DMSO in water. This was followed by soaking in cold (below the Tt) MilliQ water, with several exchanges over a 24 h period.
  • DMSO dimethylsulfoxide
  • the membranes were then submerged in a cold 0.03 M solution of Tween 20 in water with constant agitation for 15 min and rinsed thoroughly with MilliQ water for 48 h. Following this, a 0.15% solution of glycine in water was used to deactivate any residual cross-linker by reacting with any isocyanate groups still present. Further washing in cold MilliQ water was then carried out for 48 h.
  • Extracted human non-carious teeth (with approval from Queen Mary Research Ethics Committee QMREC2008/57) were stored at 4° C. in deionized water refreshed every 7 days until needed. Each tooth was carefully mounted on a holder and placed inside the diamond cut-off machine (Accutom-5, Struers A/S, Ballerup, Denmark) by aid of a compound material, the required X and Y starting positions along with Y stop position were selected and saved. Teeth were cut along their cross sections into discs, the thickness of each disk comprising both dental enamel and dentine was 500 ⁇ m.
  • the tooth sections were carefully polished using a polishing unit (Kent 4, automatic lapping and polishing unit) by aid of silicon carbide (SiC) grinding papers (CarbiMetTM) from coarse to fine as follows (P600, P1000, P2500, P4000). Subsequently, the samples were polished using polishing cloth and diamond suspension waterbase (MetprepTM) as follows (3, 1, 0.25 ⁇ m). Finally, the discs were acid etched using 6% citric acid for 2 minutes, however, enamel samples (longitudinal sections) that were used as controls for SEM images were etched using 38% phosphoric acid for 30 seconds. Fabrication of the ELP membranes in situ on dental discs was performed as described above (Membrane fabrication and ELP glass coating).
  • Samples were mounted after being dried on aluminum stubs via self-adhesive tape and were coated by auto sputter coating machine with a conductive material. Samples were analyzed using an FEI Inspect F (Hillsboro, Oreg., USA). Their surface topography was observed using a secondary electron detector. A backscattered electron (BSE) detector was used to assess the variation in density within each sample. Furthermore, the elemental analysis was carried out using INCA software. Point and mapping spectra collection at areas of interest were carried out using an EDX detector (INCA x-act, Oxford Instruments) at an accelerating voltage of 10 kV. In other instances, samples were investigated using SEM (Gemini 1525 FEGSEM), operated at 10 kV.
  • SEM Garnier 1525 FEGSEM
  • the instrument was equipped with both an inlens detector that recorded secondary electrons, and a backscatter electron detector.
  • the DDC-SEM images were obtained by imaging the same region with both intens mode and backscatter mode. Using ImageJ software, both images were stacked and the intens image was assigned to the green channel whereas the backscatter image was assigned to the red channel (Bertazzo, S. et al. Nano-analytical electron microscopy reveals fundamental insights into human cardiovascular tissue calcification. Nature Materials 12, 576-583 (2013)).
  • FIB-SEM Focused ion beam-scanning electron microscopy
  • FTIR analysis was conducted using the FTIR Spectrum GX (PerkinElmer®, Waltham, Mass., USA). Membranes before and after mineralization were placed over the IR window without any grinding but covered, then scanned. The program was set to take the average of thirty scans after subtracting the background, and were analyzed at a wavenumber of 4000 cm ⁇ 1 to 450 cm ⁇ 1 in respect to % of transmittance. The data were normalized from 500 to 1800 cm ⁇ 1 . Human non-carious dental enamel powder (kindly supplied by Prof. Colin Robinson, University of Leeds) was also analyzed for comparison purposes.
  • Powder diffraction was conducted at room temperature to elucidate the phase composition of the mineralized membrane, using an X'Pert Pro X-ray diffractometer (PANalytical, B. V., Almelo, Netherlands) with flat plate ⁇ / ⁇ geometry and Ni-filtered Cu—Ka radiation at 45 kV and 40 mA, where Ka1 and Ka2 equal 1.540598 and 1.5444260 A respectively.
  • the 20 range of the diffraction pattern was taken from 5-70° with a step size 0.0334° and data was collected continuously with an equivalent step time of 1600 seconds using a PANalytical X'Celerator solid-state RIMS detector. Rietveld refinement was performed using GSAS software40.
  • the 19 F chemical shift scale was calibrated using the ⁇ 120 ppm peak of 1M of NaF solution along with trichloro-fluoro-methane (CFCl 3 ), as a second reference. Spectra were acquired for 4 hours with accumulation of 240 scans, while for the protein membranes there was an accumulation of 4 runs each for 4 hours.
  • Live timelapse microscopy was performed using Zeiss Axiovert 200M microscope (motorized epi-fluorescence inverted microscope) equipped with a temperature-controlled chamber for live imaging. Imaging setup and acquisition was controlled by AxioVision software with a temporal resolution of 15 minutes with Zeiss AxioCam MRm camera. The objective used for the imaging was an LD Aplan 20x/0.3 Ph1 as required for phase contrast. The images were then compiled into a video for visualization. Moreover, the images were segmented using Avizo software (FEI) to allow quantitative analysis of the growth as a function of time.
  • FEI Avizo software
  • the sensitivity of cantilevers was determined before measurements by measuring the slope of the force-distance curve in the AFM software on an empty region of a petri dish. Indentation was carried out with an approach speed of 5 ⁇ m/s and a maximum set force of 1 nN. Measurements were taken multiple times per region and in multiple regions per sample. The Young's modulus was calculated by fitting the contact region of the approach curve with the Hertz Contact model (Harris, A. R. & Charras, G. T. Experimental validation of atomic force microscopy-based cell elasticity measurements. Nanotechnology 22, (2011)) using the JPK software, using the above constants and calibrated cantilever sensitivity. Graphs were plotted with GraphPad Prism software, using a P value of 0.05.
  • Spectra were recorded using a Chirascan spectropolarimeter (Applied Photophysics, UK). ELR samples were dissolved in an optimized concentration of 0.01% w/v in 0.01 mm thick cuvette. Spectra are presented with a 0.5 nm step, 1 nm bandwidth, and 0.5 second collection time per step at 4, 25, and 37° C. The post-acquisition smoothing tool from Chirascan software was used to remove random noise elements from the averaged spectra. The CD signal from the water was subtracted from the CD data of the peptide solutions.
  • Dynamic light scattering using a Zetasizer (Nano-ZS ZEN 3600, Malvern Instruments, UK) was used to measure both zeta potential ( ⁇ ) and hydrodynamic radii of the statherin-ELR molecules to investigate the charge and size respectively, at constant pH of 6.0, while varying calcium concentration whether 0 mM or 10 mM in order to investigate its calcium binding affinity at different temperatures (4, 25, 37° C.). Samples were incubated for 5 minutes at the desired temperature before measurements.
  • Membranes were fabricated as detailed above using three different ELPs comprising a statherin-derived peptide (SN), RGDS, or no bioactive segment (IK), where the only molecular difference is the presence of the bioactive sequence (Table 2).
  • SN membranes have been shown to enhance mineralisation and therefore were used as the main experimental group in this study, while RGDS membranes were used for comparison, and IK membranes and borosilicate glass substrates coated with the different ELP molecules were used as controls.
  • SN membranes have been shown to enhance mineralisation and therefore were used as the main experimental group in this study, while RGDS membranes were used for comparison, and IK membranes and borosilicate glass substrates coated with the different ELP molecules were used as controls.
  • IK membranes and borosilicate glass substrates coated with the different ELP molecules were used as controls.
  • FIG. 30 a - c distinctive hierarchically mineralized structures
  • FIG. 30 b distinctive hierarchically mineralized structures
  • FIG. 35 a - d distinctive hierarchically mineralized structures
  • the results were verified by repeating the experiments and including RGDS-containing ELP membranes and collagen membranes, and observing that the hierarchically mineralized structures formed only on ELP membranes, confirming that the ELP sequence, and not the bioactive components, is responsible for the formation of the hierarchically mineralized structures ( FIG. 35 e - f ).
  • the hierarchically-ordered crystalline structures are up to 70 ⁇ m in height and 350 ⁇ m in diameter ( FIG. 30 b - c ) when the starting pH of the solution is set to 6.0 and drops to 3.7 during mineralization.
  • much larger structures can be grown with diameters up to 1 mm when the pH is controlled throughout the mineralization process using BIS-TRIS buffer, where the pH drops from 6.0 to 5.7. It is possible that this increased growth takes place as a result of the system reaching steady-state conditions earlier under controlled pH, and therefore enabling more calcium consumption as evidenced by ion-selective electrode (ISE) measurements ( FIG. 13 d ).
  • ISE ion-selective electrode
  • the material is apatite ( FIG. 31 ) in the form of elongated needle-like nanocrystals of about 85 ⁇ 22 nm thick.
  • these crystals are organized further into enamel prism-like microstructures of about 3.8 ⁇ 0.9 ⁇ m thick and tens of microns long. These microstructures radiate outward forming the macroscopic circular structures ( FIG. 30 c - f , 33 a - d ).
  • the enamel-like structures display a remarkable periodicity of approximately 1 ⁇ m intervals ( FIG. 30 f ) along the prism-like structures, incidentally mimicking the daily incremental lines of dental hard tissues (Boyde, A. Microstructure of enamel. CIBA Foundation Symposia, 18-31 (1997)).
  • Scanning electron microscopy using the backscattered electron mode (BSE) ( FIG. 30 g - h ) and focused ion beam-scanning electron microscope (FIB-SEM) ( FIG. 30 i ) revealed that the mineralized material is present deep within the membrane in a root-like formation with a similar elongated crystallite/prism architecture, located directly below the centre of the circular macrostructures.
  • the orientation of the nanocrystals and the prism-like microstructures changed from being parallel to the surface when located on the surface of the membrane ( FIG. 30 j ) to perpendicular to the surface within the root-like structures ( FIG. 8 ).
  • the unit cell therefore has a volume of 524.1 (1) cubic Angstroms.
  • FTIR Fourier transform infra-red
  • Hierarchical CaCO 3 structures have been generated on surfaces using organic hydrogels that facilitate diffusion through the gel and the formation of an optimal ionic concentration/environment (Sakamoto, T. et al. Three-dimensional relief structures of CaCO3 crystal assemblies formed by spontaneous two-step crystal growth on a polymer thin film. Crystal Growth and Design 9 (2009)).
  • Hierarchical architecture and real structure in a biomimetic nano-composite of fluorapatite with gelatine A model system for steps in dentino- And osteogenesis? Journal of Materials Chemistry 15, 4992-4996 (2005)), synthetic hierarchical apatite structures have not been achieved.
  • the mineralized hierarchical structures reported here are the first synthetically generated material that resembles enamel in nano- and micro-morphology and chemical composition. Like enamel, the structures exhibit aligned crystallites at the nanoscale ( FIG. 33 a ), aligned prism-like and interprism-like regions with incremental lines at the microscale ( FIG. 33 c - g ), and macroscopic growth. Chemically, the structures consist of FAp rather than HAp ( FIG. 31 ), which could improve resistance to acid environments that increase during dental caries and erosion. Finally, the structures are grown on a flexible, transparent, and robust biocompatible membrane, which facilitates both its formation and functionality.
  • the structures exhibit high spatial organization at multiple length scales beginning from well-defined elongated needle-like FAp nanocrystals that come together into adjacent enamel prism-like geometries, which are organized in circular structures hundreds of microns in diameter that collectively assemble to cover macroscopic areas.
  • the structures are grown on a biocompatible, transparent, flexible, and robust ELP-based membrane, which facilitates its application.
  • Direct write laser lithograpy was used to fabricate a silicon chrome photomask.
  • a (111)-oriented silicon wafer was coated with an 8 um thick layer of SU8-10 photoresist, soft baked (65 C for 2 minutes and 950 C for 5 minutes), and then exposed through the silicon chrome photomask (30 mWcm-2 for 3.3 seconds). It was subsequently post-exposure baked (65 C for 1 min and 950 C for 5 min) and developed using SU8 developer for 30 s. Topographies were transferred to polydimethylsiloxane (PDMS) using a standard soft lithography process. The PDMS prepolymer was poured on top of the patterned master, degassed under vacuum for 7 min, and then cured at 650 C for 2 hours. The resulting topographically patterned mold was subsequently used to create membranes with the different structural components using similar dropcasting method as mentioned for the smooth membranes.
  • PDMS polydimethylsiloxane
  • FIG. 14 shows the preferential nucleation and growth of fluorapatite crystals on a channel-containing a microfabricated ELP-based membrane.
  • the membrane was fabricated according to the method described in Tejeda-Montes et al., 2012 (Tejeda-Montes, E. et al. Engineering membrane scaffolds with both physical and biomolecular signaling. Acta Biomaterialia 8, 998-1009 (2012)) and as detailed above.
  • the apatite crystals grew and arranged preferentially along the ridges of the channels and were absent in the channel grooves. Moreover, more crystals were observed to be present in areas where the horizontal and vertical sections of the channels would meet creating a 270° angle compared to flat surfaces, which could be due to reduction of the energy barrier.
  • the biomineralization system takes place within the bulk of a transparent ELP membrane ( FIG. 1 b ) when combined with a supersaturated solution in respect to apatite at physiological ionic concentrations and environmental conditions.
  • the ELP molecule used is a 32 kDa molecular weight ELP comprising a main hydrophobic framework (VPGIG) and the highly-acidic hydroxyapatite-binding statherin-derived peptide DDDEEKFLRRIGRFG ( FIG. 2 ).
  • VPGIG main hydrophobic framework
  • statherin-derived peptide DDDEEKFLRRIGRFG
  • FIG. 2 Upon incubation in the supersaturated solution as described in the methodology section, a mineralization process develops within the bulk of the ELP membrane ( FIG. 2 ), which results in the growth of a distinctive hierarchically-ordered mineralized structure ( FIG. 1 a - d - e - f - g ) on both sides of the membrane ( FIG. 20 ).
  • the structures were not observed on the collagen membrane controls ( FIG. 3 d ) while the ELP-coated glass surfaces only exhibited flat platelet-like crystals ( FIG. 3 b - c ).
  • the control ELP membranes exhibited similar hierarchical structures but less in number compared to membranes made with the statherin-derived ELP.
  • an optimum physicochemical environment within the membrane is of fundamental importance.
  • the mineralized structures exhibit a distinctive hierarchical architecture that mimics natural enamel at several lengthscales ( FIG. 1 a ).
  • the material is apatitic ( FIG. 1 h ) in the form of elongated nanocrystals of on average 85 ⁇ 22 nm thick ( FIG. 1 a ).
  • these crystals are organized further into enamel prism-like microstructures of on average 3.8 ⁇ 0.9 ⁇ m thick and tens of microns long ( FIG. 1 a ).
  • These microstructures grow radially and assemble into circular structures that can reach up to 1 mm ( FIG. 1 d ) in diameter and 70 ⁇ m in height ( FIG. 20 ), while coming together, interlocking ( FIG.
  • XRD X-ray diffraction
  • the ELP molecules exhibit a reversible-phase behavior, known as inverse transition temperature (Tt), where below its Tt, the molecules are well-solvated, surrounded by highly-ordered water structures, and possess a random coil conformation. Above the Tt, the ELP chain aggregates due to a hydrophobic collapse disturbing the ordered water molecules and gaining a ⁇ -spiral conformation. This behavior provides an opportunity when designing and modulating a 3D organic matrix environment for biomineralization (Weiner, S. & Addadi, L. Design strategies in mineralized biological materials. Journal of Materials Chemistry 7, 689-702 (1997)).
  • Dental enamel exhibits outstanding hardness and resistance to various masticatory forces and harsh intra-oral conditions thanks to its unique well-defined hierarchical mineralized structure (Boyde, A. Microstructure of enamel. CIBA Foundation Symposia, 18-31 (1997)). However, once lost, enamel cannot regenerate nor be healed clinically (Galler, K. M., D'Souza, R. N. & Hartgerink, J. D. Biomaterials and their potential applications for dental tissue engineering. Journal of Materials Chemistry 20, 8730-8746 (2010)). This situation leads to exposure of the dentinal tissue and consequently dentine hypersensitivity, a painful condition affecting 52% of the world population (Taani, D. Q. & Awartani, F.
  • Membranes were fabricated directly on both etched and rough surfaces of human dentine ( FIG. 26 a ) and mineralized for 8 days. SEM observations confirmed that the hierarchically mineralized membranes grew, adhered, and conformed to the surface of the etched dental tissues ( FIG. 26 a - b ). Integration between the hierarchical structures and the dental tissues was enhanced by decreasing membrane thickness to less than 20 m, as observed by FIB milling of the mineralized coating at dentine-membrane interface ( FIG. 26 b ). This behavior was particularly clear when growing the hierarchically mineralized coating on dentine tissue, where the growing aligned nanocrystals were observed to infiltrate and block dentinal tubules ( FIG. 26 a - b ).

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