DE19811900A1 - Biocompatible composite material useful for making bone or tooth prostheses, for coating metal, ceramic, silicon or polymer implants, or for coating textile fabrics - Google Patents

Abstract

Biocompatible composite material comprises one or more scleroproteins or their hydrolysis products and/or glycosaminoglycans homogeneously embedded in an inorganic gel. An Independent claim is also included for the production of the composite material by preparing a sol by hydrolysis of metal oxides or halides, adding scleroproteins or their hydrolysis products and/or glycosaminoglycans, and gelling the sol.

Description

The invention relates to a biocompatible composite material the basis of an inorganic gel. The composite material is bioactive and as a material for bones or teeth set, for coating implants made of metals, ceramics, Silicon or polymers and for coating textile fabrics suitable.

It is generally known that load-bearing implants (spec hip prostheses) can be equipped with covers to the Improve the biocompatibility of prostheses. Important requirement of the coatings are that they are not absorbable, are physiologically safe and bioactive, d. H. the existence Overgrowth with surrounding tissue is possible. Still is it is necessary that the coatings in the stress situation about are resistant to abrasion for several years and in their mechanical ver hold between bone and implant. This requirement conditions from previous coating materials are only too sufficiently fulfilled.

It is currently possible to electroplate implant surfaces to coat chemical processes or vacuum processes. Elec Trochemical processes require conductive substrates substance-specific and do not allow integration of biopoly meren (DE 44 31 862 C2, DE 195 04 386 A1). Vacuum process ge do not allow embedding of biopolymers and require one high technical and energy expenditure (EP 0 029 787 B1, US 4,818,512).  

A known alternative is coating by the sol-gel process with subsequent sintering. Calcium phosphate phases (WO 95/13101), TiO ₂ (WO 93/21969), ZrO ₂ and SiO ₂ gel layers (JP 95-308284, 951 031) can be deposited on implant materials. The creation of metal oxide layers with the sol-gel process is limited to the formation of bio-inert materials, ie materials without biologically active constituents, since the sintering necessary for sufficient substrate adhesion drives biologically active components or the best organic from the layers. In addition to providing adequate adhesion, the sintering of the conventional metal oxide layers also strives for sterility of the coatings.

A decisive disadvantage of the previously known methods is that due to the high excitation energies (CVD and PVD ver drive), sintering temperatures (sol-gel process) or the high substance specificity (electrochemical processes) an inte Gration of biopolymers is not possible and thus the bio layer activity is insufficient. In addition, through the purely inorganic character of the layers is too brittle Material behavior and reduced strength observed.

The object of the invention is to provide an improved composite material to indicate that an integration of biopolymers be provides and as a bone or denture material or Implant coating is suitable. The object of the invention it is also a method of manufacturing such Specify composite material.

A composite material and a Ver drive to its manufacture with the features according to  Claims 1 and 11 solved. Advantageous execution forms of the invention result from the dependent Claims.

Surprisingly, the task was accomplished with simple means can be solved in particular by scleroproteins or their hydrolysis products and / or glycosaminoglycans with Ver application of the sol-gel technique as a bioactive component in Metal oxide gels are embedded. When choosing suitable together Stable composites are created with the help of settings and technologies high hardness, wear resistance and adhesive strength, the bio are active and not absorbable. For a heat treatment to improve the physical-mechanical properties can be dispensed with entirely or at least partially. A be particular advantage of the invention is that Embedding biopolymers in an organic matrix of egg a material similar to the natural bone material a mate rial with high mechanical stability and high bioactivity provided.

Deviating from the previous sol-gel process, the Invention for the first time achieved the following special advantages become. The biocompatible materials of interest are relatively difficult to dissolve. Nevertheless, according to the invention an excellent coating quality with a homogeneous Distribution of biocompatible materials can be achieved. The biocompatible materials fulfill several functions simultaneously nen. First, they provide the bioactive desired Properties ready. In addition, education becomes clearer, trans Parente coatings of great hardness and uniformity even in ge wrestling thickness ranges. Finally, the promote bioactive materials the liability of an inventive Composite material on the respective substrate.  

The invention thus relates to a biocompatible compo sit material that contains a metal oxide gel and one or more homo gene embedded scleroproteins or glycosaminoglycans and / or hydrolysis products of these proteins, and the Use of such a composite material. The composite material favors the deposition of basic calcium phosphate Phases and is as a material for bone or dentures or for coating implants made of metals, ceramics, Silicon or polymers and for coating textile fabrics suitable. The invention also relates to a method for Production of such a biocompatible composite material.

The scleroproteins used include a group of Pro complex that support functions in biological organisms to practice. The scleroproteins are also called fibrillar proteins or linear fiber proteins. Examples of sclerotherapy Proteins are the keratins of hair, nails, feathers, wool and the like, the silk fibroin, collagen of the support and bin degewebes, the skin, the bones and cartilage that are in the connective tissue Weaving elastins and chitin-protein compounds such as B. the Conchagene.

Metal oxides of elements of II.-IV. Main and sub-group of the periodic table such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , B ₂ O ₃ , ZnO, CaO, P ₂ O ₅ or mixtures thereof, which can be used by a sol-gel process , e.g. B. by hydrolysis of the corresponding metal alkoxides according to Eq. (1), on the corresponding metal oxide sols and subsequent gel formation by neutralization, heating or concentration, is obtained, cf. JC Brinker, GW Scherer, Sol-Gel Science, Academic Press, London 1990. To modify the sol-gel layer properties, the hydrolysis process of the metal alkoxides in the presence of admixed alkyl trialkoxysilanes R-Si (OR ') ₃ and / or dialkoxysilanes R ₂ -Si (OR ') _{2 are} carried out, whereby modified metal oxide gels are formed which, based on 1 part by weight of metal oxide gel, contain 0 to 1 part by weight of R-SiO _3/2 and / or R ₂ -SiO. R is an organic alkyl radical which can contain amino, hydroxyl or alkoxy groups. R 'is an alkyl radical, primarily with 1-4 carbon atoms. With this modification, e.g. B. the elasticity and the adhesive behavior of the gel layers can be specifically improved.

The biocompatible composite material is produced in the following steps:

(1) Sol production

Production of the metal oxide sol by acidic or basic hydrolysis of metal alkoxides (including silicon compounds) or metal halides to the corresponding sols.

M (OR) _n + n / 2 H ₂ O → (MO _{n / 2} ) _Sol + n ROH (1)

M = z. B. Si, Al, Ti, Zr, Ti, B, Zn, Ca, P or mixtures thereof
R '= alkyl radical with 1-4 carbon atoms.

To modify the metal oxide sols, alkyl trialkoxysilanes P-Si (OR ') ₃ and / or dialkoxysilanes R ₂ -Si (OR') ₂ can be added before the sol formation. The hydrolysis of the corresponding metal alkoxides is preferably carried out in an aqueous, organic or mixed solvent, if appropriate with the addition of dilute mineral acid, aqueous alkali, fluoride or tertiary amines as the hydrolysis catalyst. Ethanol, acetone or dioxane is preferably used as the organic solvent. The resulting metal oxide sols are water-clear solutions with solids contents of 3-20% by weight.

(2) Formation of biocomposite sols

Add the biocomponent (one or more homogeneously embedded scleroproteins or their hydrolysis products and / or glycosaminoglycans) in dissolved or solid form to the metal oxide sol. The biocomponent can also be mixed in before or during the hydrolytic formation of the metal oxide brine if it is stable to the hydrolysis conditions (pH and solvent milieu).

(MO _{n / 2} ) _sol + biocomponent → (MO _{n / 2} + biocomponent) _sol (2).

For protein components, it is recommended the proportion keep organic solvents in the metal oxide sol low, to avoid denaturation. This can be done e.g. B. easy by removing the organic solvent by distillation with simultaneous addition of the volume-equivalent quantities Reach water. In this way you get enough stable, purely aqueous modified metal oxide brine, which with the proteinic biocomponents correspond to homogeneous biocomposite sols corresponding (2). The proportion of the biocomponent can vary Purpose 1-50% by weight based on the entire composite amount. For numerous applications, approx. 20 wt .-% biocomponent in the composite as particularly advantageous.

(3) Formation of the biocomposite gels

Bulk or volume products are produced by gelling the biocomposite sols after heating or neutralizing and then drying. Thin coatings are produced by concentrating on a support during a coating process. The gelation process results in a homogeneous embedding of the biocomponent in the inorganic gel and an effective immobilization:

(MO _{n / 2} + biocomponent) _sol → (MO _{n / 2} + biocomponent) _gel (3).

The production of layered composites can be done by conventional means Coating techniques such as dip coating, spraying ("Spray coating"), spinning ("spin coating"), brushing or Watering done. The layer thicknesses are typically in a range of 0.08. . . 2 µm. Anyone can act as a layer support substrates made of metals, Kera, which are common in medical technology mic, silicon or polymers can be used. Besides, is the impregnation of textile fabrics e.g. B. of medical Ver band material, easily possible.

Finally, to stabilize the composite material Solvent from the solidified biogel by a Drying process are removed and so-called. Xerogels are obtained in the form of bulk products or films. The aging in space temperature, heat treatment or chemical hardening may increase lead to further improvement in material properties.

For the production of biocompatible composite materials as a scleroprotein component, preferably collagen I, elastin, Fibroine or mixtures thereof are used. Alternatively or be the addition of the glycosaminoglycan component is possible Lich. Except hyaluronic acid, its derivatives and hydrolysis Products can be chondroitin sulfate, keratin sulfate or others Representatives of the substance class or mixtures are added. As Hydrolysates are preferred gelatin solutions, collagen hydro lysates or mixtures thereof. Gaining the Pro The clay component can be obtained from native sources or through genetic engineering cal production.

The addition of protein brings about a decisive improvement in Biocompatibility and mechanical properties of the first  biocompatible composite material. The cell adhesion will improved. The mechanical behavior also improves compared to known coating materials for Implan tate because by varying the composition of the composite sol Fracture toughness, modulus of elasticity, bending strength, compressive strength, Substrate adhesion and wear parameters of the resulting bio compatible composite material can be optimized.

A modification of the biocompatible composite material can using chemical hardening agents. These are bi- or polyfunctional connections with side chains of the amino acids of scleroproteins react so that a intermolecular networking takes place. Typically this is Share of the crosslinking agent used less than 1% by weight of the biocompatible composite material. It can anor ganic crosslinkers (e.g. chrome and aluminum salts) or organic crosslinking agents (e.g. diimides, diisocyanates, Epoxides, formaldehyde or dialdehydes) can be used. The chemical hardening leads to increased stability of the com posits in physiological media, to improved mechanical Properties and prevents the metabolism of the compo sits. Further property modifications of the biocompatible Composite material can be bioactive by adding special Receive active ingredients or active ingredient mixtures for the composite sol become. Additions of up to 5% by weight (based on the solids content of the composite). Under bioactive effect broad-spectrum antibiotics (e.g. gentamycin, Erythromycin or colistin). Through the antimicro The biological effects of the antibiotics reduce the risk of infection in the Connection with implantation reduced. Under bioactive Active substances are also to be understood as substances that are the one can accelerate the growth of the implant in bone tissue. For this, e.g. B. hormones, growth factors, cytokines or Signal peptide sequences can be used. The most famous Active substances of the substance classes include TGF β, BMP-2,  RGD peptides or calcitonin. Simple verbs are included such as O-phosphoserine, aspartic acid, glycine, arginine or their derivatives. The improved ingrowth favors the Healing process and leads to that earlier with rehabilitation measures can be started after the operation.

By adding calcium salts, phosphates or basic Calcium phosphate suspensions in concentrations up to 30% by weight can further modify the biocompatible composite material become. In this way, mechanical properties can ver improves and the bioactivity of the composite material continues be raised.

The composite material according to the invention is a material for the bone or dentures. The xerogel can follow Mills are pressed as granules into molded parts, which as Im plantate suitable for repairing bones and tooth defects are.

In addition, the biocompatible composite material is advantageous adheres to the coating of implants made of metal or other materials. It is typically used as Coating on load-bearing implants made of titanium and NEN alloys, e.g. B. hip prostheses, orthodontic Im implants or prosthetic knees. It is characteristic that the Ver Using the material as a coating the bioactivity of the metallic material significantly improved. The biocompa Compatible material induces the Ab in vitro or in vivo separation of basic calcium phosphates. Due to the high proportion protein adhesion improves cell adhesion on the Material. Due to the good substrate adhesion on difference This is suitable for substrates (e.g. glass, titanium, silicon) biocompatible composite material also as coating on other non-resorbable implants.  

The biocompatible composite material is also suitable for Impregnation of textile fabrics, e.g. B. of medical Ver band material. The impregnation leads to good skin tolerance improved mechanical stability and a controllable water absorption depending on the protein content Fabric.

The advantages of the biocompatible composite material according to the invention exist over the previous coatings

• 1. in the combination of high biocompatibility with good ones mechanical properties both in bulk products as well for coatings,
• 2. Load-bearing in the improved mechanical adjustment Implants (e.g. hip prosthesis) by applying the material as an intermediate layer between prosthesis and bone tissue,
• 3. less thermal pretreatment of the material, which involve the embedding of thermally unstable scleroproteins and the associated high biocompatibility of the composite material enables
• 4. Possibility of changing proteins and recipe Active substances (e.g. antibiotics or interleukins) in the Be being able to embed layering,
• 5. good adhesion to different implant mats rialien and high wear resistance of the modified upper planes,
• 6. in the possibility of varying the proportions between inorganic sol and scleroprotein mechanical Adapt properties to the later application,
• 7. in terms of device technology, energy and time Expenditure for the production of the composite material,
• 8. in the creation of non-brittle, deformable composite materials rials, the appearance of long-term loosening symptoms counteracts bone or dentures, and
• 9. in favor of the deposition of basic calcium powders phases.

The biocompatible composite material according to the invention is suitable therefore particularly as a material for the bone or tooth replacement, for coating metal implants, Kera mic, silicon or polymers as well as for the impregnation of textiles Tissue.

Embodiments example 1

10 ml of tetraethoxysilane, 40 ml of 1,4-dioxane and 20 ml of 0.01 M hydrochloric acid are stirred at room temperature for 20 h. A stable SiO ₂ sol A is obtained (solids content approx. 4.2% in 70% 1,4-dioxane, pH approx. 2.0).

7 ml of Sol A are mixed with 7 ml of water, 2.3 ml of a commercial aqueous 10% ZrO ₂ sol (MERCK KGaA, Darmstadt) and 10 g Collapur solution (1% collagen I solution, Grünau Illertissen GmbH , Illertissen) mixed. A clear sol is created. The dip coating of a titanium test specimen 1 × 4.4 cm ² (drawing speed 30 cm / min) after drying in air gives a transparent coating of approx. 1 µm thickness, which contains approx. 16% collagen by weight.

The mechanical testing of the coating revealed that Vickers hardness HV 0.0008 a value of 44 (nanoindenter SHIMADZU DUH-202, 0.08 p test load, penetration depth: 126-381 nm). The layer wears itself at a test load of 122 g not after 2000 friction cycles (oscillating spherical tribometer, Ball diameter 5 mm, movement frequency 3 Hz).

The immersion of the coated test object in a simulated Blood fluid resulted in the separation of basic Cal after 12 h ciumphosphate on the layer surface. (Test according to S. Li, Q. Liu, J. de Wijn, K. de Groot, B. Zhou J. Materials Sci. Lett. 15 (1996) 1882 ff.).  

The test subject was also involved in cell culture tests Cell line L 929 (lung fibroblast mouse) for cell adhesion checked within 24 hours. The quantitative comparison was made after MTT test, i. H. Synthesis of a formazan dye by Akti vity of cellular succinate dehydrogenase (cf. E. Winter mantel, S. Ha "Biocompatible materials and construction methods", Sprin ger Verlag 1996, pp. 68-80.). The evaluation of cell growth resulted in an increase to 111% (uncoated for comparison 100% glass).

Example 2

100 ml of tetraethoxysilane, 400 ml of ethanol and 200 ml of 0.25% ammonia solution are stirred at room temperature for 20 h. A stable SiO ₂ sol B is obtained (solids content 4.2% in 70% ethanol, pH = 9.2).

A solution of 1.3 g of the collagen hydrolyzate Nutrilan I-50 (Grünau Illertissen GmbH, Iller Tissen) in 5 ml of 0.1 M NH ₄ Cl / NH ₃ buffer is carefully added dropwise to 200 ml of sol B. A clear, slightly yellowish sol is formed (viscosity at 20 C = 3.5 mPas). The dip coating of a 2.5 × 7.5 cm ² glass plate (drawing speed 30 cm / min) after drying in air gives a transparent coating of approximately 0.4 μm thickness, which contains approximately 7.1% by weight of biopolymer.

The mechanical testing of the coating revealed that Vickers hardness HV 0.0008 a value of 21.

The immersion of the coated test object in a simulated Blood fluid resulted in the separation of basic Cal after 12 h ciumphosphate on the layer surface.

Example 3

80 ml of tetraethoxysilane, 20 ml of 3-glycidyloxypropyl trimethoxysilane (GLYMO), 400 ml of 1,4-dioxane and 200 ml of 0.01 N hydrochloric acid are mixed and stirred for 20 hours at room temperature. A stable SiO ₂ sol C (approx. 5.0% solids content) is obtained.

4 g of inert gelatin (FEW Wolfen) are dissolved in 96 ml of 0.01 N HCl solution solution and adjusted to pH 4.0 with 1 N HCl solution. 80 ml of the gelatin solution are added dropwise to 120 ml of Sol C. It a clear composite sol is created.

The dip coating of a 2.5 × 7.5 cm ² glass plate (drawing speed 30 cm / min) gives, after drying in air, a transparent coating of approx. 1 µm thickness, which contains approx. 35% by weight of biopolymer.

The immersion of the coated test object in a simulated Blood fluid resulted in the separation of basic Cal after 12 h ciumphosphate on the layer surface.

Furthermore, the biocomposite sol described above, which was obtained by mixing the sol C with 4% gelatin solution, was used to coat a technical polyamide fabric (two-roll pad, 0.5 m / min roll speed). After the samples had been dried at 4 h / 60 ° C., tensile strength tests were carried out on 2 × 6 cm ² strips, the strips being stretched in the longitudinal direction until they broke. The maximum tensile force was as follows: 1170 N for untreated strips, 1320 N for the strip impregnated with biocomposite sol.

Example 4

100 ml of tetraethoxysilane, 400 ml of ethanol and 200 ml of 0.01 M hydrochloric acid are stirred at room temperature for 20 h. 600 ml of the sol thus obtained are mixed with 420 ml of water. The mixture is heated in a distillation apparatus on the boiling water bath and 420 ml of ethanol are distilled off. After cooling, a stable aqueous SiO ₂ sol D (solids content 4.2% in water, pH = 2.3) is obtained.

25 ml of Sol D are mixed with 1,357 g of 1% hyaluronic acid solution (GfN, production of Naturextrakte GmbH, Wald-Michelbach) mixed. A clear, viscous sol (viscosity = 51.7 mPas at 20 ° C).

The dip coating of a 2.5 × 7.5 cm ² glass plate (drawing speed 15 cm / min) results in a transparent coating of approx. 1 µm thickness after drying in air.

The mechanical testing of the coating revealed that Vickers hardness HV 0.0008 a value of 76. The layer ver wears at a test load of 222 g even after 2000 rubs don't cycle.

The immersion of the coated test object in a simulated Blood fluid resulted in the deposition of more basic after 12 h Calcium phosphates on the layer surface.

Claims (14)

1. Biocompatible composite material consisting of an anorga niche gel and a bioactive component, one or more homogeneously embedded scleroproteins or their hydrolysis pro products and / or glycosaminoglycans. 2. Biocompatible composite material according to claim 1, characterized characterized in that the inorganic gel oxides of elements the II.-IV. Main and subgroup of the periodic table ent holds. 3. Biocompatible composite material according to claim 1 and 2, characterized in that the inorganic gel by Hydro lysis products of trialkoxysilanes and / or dialkoxysilanes mo is differentiated. 4. Biocompatible composite material according to one of claims 1 to 3, in which the scleroproteins collagen, elastin and / or Fibroin include. 5. Biocompatible composite material according to one of the previously going claims, characterized in that as hydrolysis products of the scleroproteins collagen hydrolyzates, gelatin or Amino acid combinations from glycine, arginine, aspartic acid or O-phosphoserine can be used. 6. Biocompatible composite material according to one of the previously going claims, characterized in that as Glycosaminoglycane hyaluronic acid or chondroitin derivatives be used.   7. Biocompatible composite material according to one of the previously going claims, characterized in that the proportion of Scleroproteins or their hydrolysis products and / or the Glycosaminoglycans 1-50 wt .-% based on the composite is. 8. Biocompatible composite material according to one of the previously claims, characterized in that antibiotics, Cytokines, hormones or signal peptides in concentrations up to 5% by weight based on the composite are included. 9. Biocompatible composite material according to one of the previously going claims, characterized in that the composite 1-30 wt .-% based on the composite calcium phosphate or contains their precursors in dissolved or dispersed form. 10. Biocompatible composite material according to one of the previously outgoing claims, characterized in that the material favors the deposition of basic calcium phosphate phases and as a material for bone or dentures or for Coating of implants made of metals, ceramics, silicon or polymers or suitable for coating textile fabrics is. 11. Process for making a biocompatible composite terials according to one of claims 1 to 10, wherein an anor ganic sol by hydrolysis of metal alkoxides or metal halides produced and the inorganic sol for formation of a biocomposite sol the bioactive component in the form of Scleroproteins, their hydrolysis products and / or the Glycosaminoglycane added and then the Biokompositsol ge is gated.   12. The method of claim 11, wherein the gelling a heat change, neutralize and / or dry the biocomposite sol sums up. 13. The method according to claim 11 or 12, wherein the biocompo sitsol is applied in layers on a substrate and is gelled there. 14. The method according to claim 11 or 12, wherein the biocompo sitsol is gelled in volume form.