Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/40—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
  • A61L27/44—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/36—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix
  • A61L27/3604—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix characterised by the human or animal origin of the biological material, e.g. hair, fascia, fish scales, silk, shellac, pericardium, pleura, renal tissue, amniotic membrane, parenchymal tissue, fetal tissue, muscle tissue, fat tissue, enamel
  • A61L27/3608—Bone, e.g. demineralised bone matrix [DBM], bone powder
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2430/00—Materials or treatment for tissue regeneration
  • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants

Definitions

• the present invention relates to implant matrixes to be used generally in the bone reconstructive surgery field, in orthopaedics and in particular in oral surgery, in dental and maxillo-facial implantology .
• DBM Demineralized Bone Matrixes
• acellularization treatments also called Bone Graft, as for example those produced by Geis- tlich SA, Switzerland and RTIBiologics, USA, etc.
• tissue engineering an approach wherein grafts are used that are made of osteoconductive and osteoinductive materials, such as e.g. some bioglasses
• regenerative medicine where artificial or semi- artificial matrixes are used in order to host and deliver living cells to target area and thus enhance the formation of new resistant bone.
• Choosing an implant material is based on the osteogenesis, osteoinduction and osteoconduction properties of the material thereof.
• the quantity of material available to prepare the implant is limited and moreover the patient must undergo a dual intervention, the first for removing autologous bone and the second for the subsequent implant .
• an alternative way is represented by the usage of homologous tissue, that is the usage of demineralised bone matrix (DBM) .
• DBM demineralised bone matrix
• the DBM is obtainable by a living donor, by a donor corpse or an animal.
• the human cortical derived DBM has the same drawback of the autologous bone, i.e. the quantity of available material appears to be reduced. Further risks exist connected to possible infections, in particular viral and to potential compatibility problems, since the material to be implanted is of a heterologous nature. Moreover, the psychological aspect for the recipient, above all when the material is corpse-derived, represents an unnegligible critical element.
• the DBM may be of animal origin, in particular bovine.
• a microscopic examination can show that the bovine DBM porosity is higher than the cortical-derived human DBM, with a resulting minor compatibility and a reduced predisposition to the cell rooting and the growth of new integrated functional tissue.
• the Applicant has observed that the higher porosity and the chemical structure of the bovine DBM result into a lower mechanical resistance, with a consequent higher weakness thereof.
• Such a weakness is particularly disadvantageous both in the pre- implant step, since shaping the matrix, according to the shape of the bone cavity which will host the matrix itself, with the desired accuracy is not easy, and in the implant in situ positioning step, because of the poor toughness of the matrix itself, which is often subject to a fragile fracture during the clamping steps .
• the shaping step of the matrix currently available in the state of the art such as, for example, demineralised bone matrixes (DBM) , Ac- lularised (bone grafts), bioglasses, bio-ceramics, etc.
• DBM demineralised bone matrixes
• the shaping step takes place just before the implantation and the resulting powders creep up also on the matrix to be implanted.
• Another proposed solution is a composite osteoim- plant described in US2008/0063684.
• Such an osteoim- plant includes a polymer and bone-derived particles. The composite is adapted and constructed to be form- able during or immediately prior to implantation and to be set after final surgical placement.
• US 7.270.813 describes a method for preparing bone-derived composites, wherein the mineral portion of the bone is treated with a coupling agent before being incorporated into a biocompatible polymeric matrix.
• the resulting composite may be used as such that or be further processed to form an osteoimplant .
• Object of the present invention is a matrix for bone implant, comprising a base matrix either treated or to be treated with a mixture containing at least a polymer .
• the bone implant matrix object of the present invention is suitable to be used in the bone reconstructive surgery field in general, in orthopaedics and in particular in the oral surgery, in the max- illo-facial and dental implantology .
• FIG. 1 is an optical microscopy image of the cortical layer of human bone
• FIG. 2 is an optical microscope image of a bovine-derived purified bone
• - Figure 3 is an optical microscope image of a bovine-derived bone reinforced according to a preferred embodiment of the invention
• - Figure 4 is a scanning electronic microscope (SEM) image of a section of a bone implant matrix made according to a preferred embodiment of the invention which subsequently underwent a cell seeding, with chondrocyte-type cells, though the micro-seeding technique. The image was obtained on the third day after the seeding;
• FIG. 5 shows graphs of the monoaxial mechanical crushing strength of a bovine-derived acellular- ised matrix (untreated) and an analogous matrix, treated according to an example of the invention.
• a bone implant matrix comprises: a) a base matrix treated or to be treated with b) a reinforcing mixture containing at least a polymer .
• base matrix a substantially solid tri-dimensional body is meant, intended, typically porous, after a treatment described herein below, to be implanted in bone cavities.
• the base matrix may be synthetic or natural.
• the synthetic base matrixes may be, for example, polymeric, metallic, ceramic, bio-ceramic, bio-glass matrixes.
• the natural base matrixes may be se- lected, for example, from demineralised bone, non- demineralised bone, acellularised bone, natural polymeric, mineral matrixes.
• the acellularised bone matrixes are non-demineralised matrixes completely (or substantially) devoid of the donor's cellular material.
• the human corpse-derived bone matrixes are preferred and the animal-derived demineralised, non-demineralised, acellularised bone matrixes are particularly preferred, in particular, preferably, bovine.
• polymeric type synthetic base matrix are preferred, in particular of bio-compatible polymers .
• the bone implant matrixes may have different shapes and dimensions, such as to be adapted according to the shape and the dimensions of the bone cavities, where said matrixes can be implanted.
• such bone matrixes may be parallelepiped-shaped, in particular cube-shaped.
• the dimensions of the bone implant matrixes can vary from a few mm till some dm of maximum length.
• Basic matrixes are usually porous.
• the base matrix and the polymer (s) of the reinforcing mixture are advantageously bio-compatible.
• the base matrix and/or the polymer of the reinforcing mixture are preferably bio- integrable, in order to better assist the growth of the new bone integrated with the surrounding tissue.
• the expression "reinforcing mixture” it is meant a mixture comprising at least a polymer, i.e. which comprises only one polymer or, alternatively, it may be multi-polymeric, i.e. may comprise more than one polymer at the same time.
• reinforcing mixture it is meant a mixture, wherein the synthetic or natural, and advantageously bio-compatible, polymer or polymers, are finely dispersed.
• a reinforcing mixture obtained starting from two solutions, each of them made of a soluble polymer and an agent promoting the cell engraftment, growth and proliferation, and the tissue integration, respectively, immiscible to each other, but made partially miscible by adding an alcohol or another proper solvent in each of them; in order to obtain a fine and homogeneous molecular dispersion of the components, which, during the solvent evaporation step creates a homogeneous coating, finely dispersed on the whole surface of the porous bone matrix, i.e. coating it also in the inner cavities, without closing them, though.
• the polymer of the reinforcing mixture may be selected, for example, from the group comprising biodegradable polymers, non-biodegradable polymers, copolymers of the biodegradable polymers, co-polymers of the non-biodegradable polymers, co-polymers of the biodegradable and non-biodegradable polymers.
• the biodegradable polymers are selected from poly (arylates) , poly (acrylates) , poly (anhydrides) , poli (hydroxyacids) , polyesters, poly (orthoesters) , polycarbonates, poly (propylene fu- marates) , poly (amide esters), poly (amide carbonates), polyamides, polyaminoacids, polyacetals, polylac- tides, polyglycolides, poly (dioxanones) , polyhydroxy- butyrate, polyhydroxyvalerate, polyvinyl pyrrolidone, polycyanoacrylates, polyurethanes, polyalkylene oxides, polyamino carbonates, polyester amides, polyester imides, aminoacid polyarylates, aminoacid polycarbonates, polysaccharides, poly-ethylene-glycole and tyrosine-based polymers, comprising polyarilates, polyacrylates and polycarbonates.
• polyesters are preferred, in particular polylactic acid (PLA) , poly- glycolic acid (PGA), polycaprolactone (PCL) and copolymers thereof, such as for example polycaprolac- tone-polylactic (PLA/PCL) co-polymers, poly (L- lactide-co- ⁇ -capcolactone) co-polymers .
• PLA polylactic acid
• PGA poly- glycolic acid
• PCL polycaprolactone
• copolymers thereof such as for example polycaprolac- tone-polylactic (PLA/PCL) co-polymers, poly (L- lactide-co- ⁇ -capcolactone) co-polymers .
• non-biodegradable polymers these may be selected from polypyrrole, polyanilines, polythiophene and derivates thereof, polystyrene, polyurethanes, polyureas, poly (ethylenevinylacetate) , polypropylene, polymethacrylate, polyethylene, poly (ethylene oxide) .
• the polymer may be selected from the group comprising starch, poly (caprolactones) , poly (L-lactide) , poly (D, L- lactide-co-glycolide) , poly (L-lactide-co-D, L- lactide) , their enantiomers, their co-polymers and mixtures thereof.
• the reinforcing mixture may comprise, beside the polymer or the polymers, at least an additional component selected from cell nutrients, cell-growth promoters, cell-adhesion promoters, osteoinductors, os- teointegrators, "friendliness to cell”.
• the expression “friendliness to cell” it is meant a substance, which is able to promote the cell- rooting and the cell growth, by stimulating cell proliferation and tissue integration.
• the “friendliness to cell” may be selected from the group consisting of glycosaminoglycanes; polysaccharides comprising agarose, dextrane, chitosane; fibrin, fibrinogen and derivates thereof; collagen of any kind and derivates thereof; hyaluronic acid and derivates thereof; vitamins, such as vitamin D; soya- isoflators comprising genestein; drugs, which reduce the bone destruction and stimulate the bone reconstruction, for example drugs used in treating the osteoporosis comprising strontium ranelate and the use of gelatine, in particular hydrolysed, as “friendliness to cell” is particularly preferred.
• the presence of at least one “friendliness to cell” assists the cell rooting and growth, since the cell proliferation and the tissue integration are promoted and this is an important advantage in respect to
• the solvents used to prepare the reinforcing mixture are commonly known in the state of the art and may be, for instance, dichloromethane, tetrahydrofu- ran, isopropanol, etc., and their specific use results from the kind of polymer/s used, according to the well-known laws of chemistry.
• a particularly preferred embodiment of the bone implant matrix comprises a base matrix, which is a bovine demineralised bone matrix treated with a reinforcing mixture comprising a biodegradable polyester- based co-polymer, such as, for example, a poly- caprolactone-polylactide co-polymer (PLA/PCL) and, preferably hydrolysed, gelatine.
• a base matrix which is a bovine demineralised bone matrix treated with a reinforcing mixture comprising a biodegradable polyester- based co-polymer, such as, for example, a poly- caprolactone-polylactide co-polymer (PLA/PCL) and, preferably hydrolysed, gelatine.
• PLA/PCL poly- caprolactone-polylactide co-polymer
• the bone implant matrix comprises a base matrix, which is a bovine non-demineralised accellu- larised bone matrix, treated with a reinforcing mixture comprising a biodegradable polyester-based copolymer, such as, for example, a poly (L-lactide-co- ⁇ - caprolactone) , and preferably hydrolysed, gelatine.
• a base matrix which is a bovine non-demineralised accellu- larised bone matrix, treated with a reinforcing mixture comprising a biodegradable polyester-based copolymer, such as, for example, a poly (L-lactide-co- ⁇ - caprolactone) , and preferably hydrolysed, gelatine.
• the reinforcing mixture comprises at least a biodegradable polyester and at least a "friendliness to cell".
• a kit comprising the reinforcing mixture in a proper separate container and the base matrix to be treated.
• the bone implant matrixes described above may be used in the orthopedic, oral surgery, the bone reconstructive surgery and implantology .
• Said bone implant matrixes are particularly suitable to be used in oral surgery, in maxillo-facial and dental bone reconstructive surgery, in particular to reconstruct and consolidate the bone structures before carrying out the insertion of dental implants.
• said bone implant matrixes are particularly suitable in the bone reconstructive surgery, following the decrease in the bone mass in patients affected by osteoporosis.
• said bone implant matrixes may be used also in oral and dental applications, dentistry, as bone "chips”, as support matrixes for cell housing and in cellular therapies.
• the bone implant matrixes may be used for both human and veterinary use.
• a method for preparing the bone implant matrixes comprises the following steps: a) preparing a solution of a reinforcing mixture containing at least a polymer, b) immersing a base matrix into the reinforcing mixture made according to step a) , c) drying and degassing the matrix made according to step b) , preferably in a vacuum furnace at 37 0 C ( ⁇ 2°C) for 24 hours, for removing possible solvent residues (for example in air or preferably in a vacuum furnace) . Drying and degassing the bone implant matrix usually take place contemporarily.
• Such a method may optionally be followed by a post-treatment step, which comprises for example heating, conditioning in a inert atmosphere the bone implant matrixes and degassing to remove completely the possible residues of solvents used in the preparation process.
• a post-treatment step comprises for example heating, conditioning in a inert atmosphere the bone implant matrixes and degassing to remove completely the possible residues of solvents used in the preparation process.
• the bone implant matrix preparation process may be followed by a packaging method which comprises the steps of: d) packaging in a sterile and inert atmosphere, e) sterilization (preferably through either gamma-ray or beta-ray irradiation) .
• the matrixes known in the state of the art and commonly used in the orthopaedic surgery have poor mechanical resistance, poor fixing resistance, fragility and little ductility characteristics.
• the Applicant has surprisingly found that, by treating a base matrix with a reinforcing mixture containing at least a polymer, as described above, it is possible to obtain bone implant matrixes, which have such ductility characteristics as to make easier shaping, in the pre-implant step, the bone implant matrix, with the desired accuracy, in relation to the bone cavity, which will host the matrix itself.
• the mechanical resistance of the bone implant matrixes determines a reduced trend to the fragile fracture of the matrixes themselves, this is particularly advantageous both in the implant in situ positioning step and in the positioning and insertion of clamping elements (for example screws), of such a matrix.
• Figure 5 depicts two graphs of monoaxial mechanical crushing strength: the curve "untreated” refers to a bovine-derived acellularised matrix and the curve “treated” refers to an analogue acellularised matrix, treated with a reinforcing mixture, containing at least one polymer, as previously disclosed.
• the clear comparison indicates how the previously disclosed treatment allows the matrix to be stiffer (increased modulus of elasticity, or Young's modulus) and have a higher load resistance (maximum effort, in MPa) .
• the bone implant matrixes may be subject, during the pre-implant step, to a possible cell-seeding process .
• the cells can be seeded by using seeding techniques known in the state of the art, preferably with micro-seeding technique after the matrix has been brought to a temperature of 37 0 C (preferably in an incubator) .
• the seeded bone implant matrix is then covered with a proper culturing medium and kept inside the incubator according to the techniques commonly required by the cell type used.
• the cell optimal load is about 300000-500000 cell/cm 3 .
• Figure 4 shows how the bone implant matrix according to an embodiment of the invention allows the cell rooting, due to the porosity characteristics, in terms of both dimensions and available spaces.
• EMBODIMENT EXiAMPLE 2B Method for preparing a bone implant matrix.
• EMBODIMENT EXAMPLE 2C Method for preparing a bone implant: matrix.
• Figure 1 shows an image obtained by the optical microscope of a human bone cortical layer, which presents the desirable porosity and mechanical resistance characteristics.
• Figure 2 shows an image obtained by an optical microscope of a bovine demineralised bone matrix.
• Figure 1 shows an image obtained by an optical microscope of a bovine demineralised bone matrix.
• the bovine demineralised bone matrix in figure 2 which represents a "base matrix” according to an embodiment of the invention, underwent a treatment with a reinforcing mixture containing at least a polymer, in particular containing a polycaprolactone- polylactic co-polymer (PLA/PCL) and hydrolysed gelatine .
• a reinforcing mixture containing at least a polymer, in particular containing a polycaprolactone- polylactic co-polymer (PLA/PCL) and hydrolysed gelatine .
• PLA/PCL polycaprolactone- polylactic co-polymer
• the microscopic structure of the bone implant matrix in figure 3 obtained according to an embodiment of the invention shows strong similarity to the human bone cortical layer.
• the porosity which appears completely comparable in terms of both dimensions and available spaces for the cell rooting.

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• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Oral & Maxillofacial Surgery (AREA)
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• 2008
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