HYDROXYAPATITE/GELATIN COMPOSITE MATERIAL AND THE USE OF SAME, PARTICULARLY AS ARTIFICIAL IVORY, AND METHOD FOR PRODUCING SAME

Abstract

The invention relates to a method for producing a multi-purpose isotropic hydroxylapatite/gelatine composite material, involving at least the following steps: a) providing a suspension of powdered hydroxylapatite in a liquid medium selected from the group comprising a C1-C10 alcohol, particularly ethanol, another dispersing agent that can be mixed with water, water, and mixtures thereof; b) adding an aqueous solution of gelatine, preferably at a concentration of 5 to 25 wt. % gelatine, to the suspension; c) agitating the mixture at a predefined temperature for a predefined period of time, preferably in the region of 1 to 10 hours, until the liquid medium has been fully or partially evaporated; and d) optionally drying the product obtained in step c). In a specific embodiment, the method is characterised in that the product obtained in step c) or d) is additionally infiltrated with at least one aliphatic polyether in an additional step e1). In another specific embodiment, the method is characterised in that the product obtained in step c), d) or e1) is additionally brought into contact with at least one agent for crosslinking the gelatine chains, in step e2). A further aspect of the invention relates to the composite material produced using the method described above, and the use of same, particularly as artificial ivory.

Claims

1. A method for producing an isotropic hydroxyapatite/gelatin composite material, which comprises at least the following steps: a) providing a suspension of powdery hydroxyapatite in a liquid medium selected from the group consisting of a C.sub.1-C.sub.10 alcohol, another water-miscible dispersant, water and mixtures thereof; b) adding an aqueous solution of gelatin, in a concentration of 1 to 40% by weight of gelatin, to the suspension to provide a mixture; c) agitating/stirring the mixture at a predetermined temperature for a predetermined period of time until partial or complete evaporation of the liquid medium; and d) optionally drying the product obtained in step c).

2. The method according to claim 1, wherein step c) is carried out at a temperature below a boiling point of the liquid medium obtained after step b).

3. The method according to claim 1, wherein a product obtained in step c) or d) is further infiltrated in an additional step e1) with at least one aliphatic polyether.

4. The method according to claim 1, wherein a product obtained in step c) or d) is further contacted in a step e2) with at least one crosslinking agent for crosslinking gelatin chains.

5. The method according to claim 4, wherein the at least one crosslinking agent is selected from the group consisting of complex-forming metal salts, aldehydes, ketones, epoxides, isocyanates, carbodiimide and enzymes.

6. The method according to claim 5, wherein the complexing metal salt is selected from the group consisting of salts of aluminum, chromium, iron, titanium, zirconium, and molybdenum.

7. The method according to claim 3, further comprising at least the following steps: e1a) contacting the product obtained in step c) or d) of claim 1 with a medium containing a mixture of poly ether/water for a predetermined period, and e1b) subsequently exchanging the medium for an anhydrous medium comprising an aliphatic polyether and contacting a product obtained after step e1a) with the aliphatic polyether for a predetermined period of time.

8. The method according to claim 3, wherein the contacting with the polyether is carried out under reduced pressure or under vacuum.

9. The method according to claim 4, wherein the product obtained in step c), or d) is contacted for a predetermined period, with a crosslinking agent and then, optionally after removing the at least one crosslinking agent and washing, the product is dried.

10. The method according to claim 4, wherein only a partial area of the product obtained in step c) or d) is contacted with the at least one crosslinking agent and the gelatin matrix is crosslinked only in the partial area.

11. The method according to claim 10, wherein a superficial contact is effected by repeated application of the at least one crosslinking agent on a surface of the composite material.

12. The method according to claim 3, wherein the at least one aliphatic polyether has a molecular weight in a range from 100 to 10,000,000 g/mol.

13. The method according to claim 3, wherein the at least one aliphatic polyether is a polyethylene glycol.

14. An isotropic hydroxyapatite/gelatin composite material, obtainable by the method according to claim 1, which contains hydroxyapatite particles with dimensions in a nanometer range randomly embedded in an amorphous gelatin matrix.

15. The composite material according to claim 14, wherein the hydroxyapatite particles represent or comprise hydroxyapatite needles with dimensions in the nanometer range.

16. An isotropic hydroxyapatite/gelatin composite material, obtainable by the process according to claim 3, which contains an aliphatic polyether embedded in the gelatin matrix and/or crosslinked gelatin chains, wherein acid groups of amino acids in the gelatin chains are crosslinked via metal complexes.

17. The composite material according to claim 16, wherein the aliphatic polyether has a molecular weight in a range from 100 to 10,000,000 g/mol.

18. The composite material according to claim 16, wherein the aliphatic polyether is a polyethylene glycol.

19. The composite material according to claim 15, which has the following composition: 50 to 100% by weight of hydroxyapatite/gelatin matrix with a hydroxyapatite/gelatin ratio of 1:1 to 10:1, 0 to 30% by weight of residual liquid medium, and optionally 0.5 to 50% by weight of polyether.

20. The composite material according to claim 14, which further comprises one or more additives selected from the group consisting of pigments, dyes, phosphors, materials for marking materials, salts, metal particles, polymers, glasses, fibers, and antimicrobial components.

21. The composite material according to claim 14, which is ivory-colored.

22. An artificial ivory comprising the composite material according to claim 14.

23. The composite material according to claim 14, which is configured for use as at least a part of key coverings for keyboards, handles/grip inserts, watches, model components, toys, office utensils, writing utensils, dishes, kitchen appliances, clothing accessories, sanitary items, pharmaceuticals, electronic components, building materials, construction materials, lamps, interiors for cars, jewelry items, coatings, eyeglass frames, a moisture-regulating material and a plastic substitute.

24. The composite material according to claim 14, which has the following composition: 50 to 100% by weight of hydroxyapatite/gelatin matrix with a hydroxyapatite/gelatin ratio of 1:1 to 10:1, 0 to 30% by weight of residual liquid medium, and optionally 0.5 to 50% by weight of polyether.

25. The composite material according to claim 15, which further comprises one or more additives selected from the group consisting of pigments, dyes, phosphors, materials for marking materials, salts, metal particles, polymers, glasses, fibers and antimicrobial components.

26. The composite material according to claim 15, which is configured for use as at least a part of key coverings for keyboards, handles/grip inserts, e.g., for sports equipment, tools and knives, watches, model components, toys, office utensils, writing utensils, dishes, kitchen appliances, clothing accessories, sanitary items, pharmaceuticals, electronic components, building materials, construction materials, lamps, interiors for cars, jewelry items, coatings on wood and other materials such as glass, plastics or metals, e.g., for interior fittings, eyeglass frames, or as a moisture-regulating material and as a plastic substitute.

27. An artificial ivory comprising the composite material according to claim 15.

28. An artificial ivory comprising the composite material according to claim 16.

29. The method according to claim 3, wherein the product obtained in step e1) is further contacted in a step e2) with at least one agent for crosslinking the gelatin chains.

30. The method according to claim 29, wherein the at least one crosslinking agent is selected from the group consisting of complex-forming metal salts, aldehydes, ketones, epoxides, isocyanates, carbodiimide and enzymes.

31. The method according to claim 30, wherein the complexing metal salt is selected from the group consisting of salts of aluminum, chromium, iron, titanium, zirconium and molybdenum.

32. The method according to claim 29, wherein only a partial area of the product obtained in step e1) is contacted with the at least one crosslinking agent and the gelatin matrix is crosslinked only in the partial area.

33. The method according to claim 32, wherein a superficial contact is effected by repeated application of the at least one crosslinking agent on a surface of the composite material.

34. The method according to claim 29, wherein the aliphatic polyether has a molecular weight in a range from 100 to 10,000,000 g/mol.

35. The method according to claim 29, wherein the aliphatic polyether is a polyethylene glycol.

36. The method according to claim 3, wherein a product obtained in step e1) is contacted for a predetermined period with a crosslinking agent, and then, optionally after removing the at least one crosslinking agent and washing, the product is dried.

37. The method according to claim 36, wherein the at least one crosslinking agent is a solution of a complexing metal salt.

38. The method according to claim 1, wherein the C.sub.1-C.sub.10 alcohol is ethanol.

39. The method according to claim 6, wherein the complexing metal salt is an alum.

40. The method according to claim 31, wherein the complexing metal salt is an alum.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0074] FIG. 1 shows photographs of an isotropic composite material according to the invention;

[0075] FIG. 1A shows the hydroxyapatite/gelatin composite raw material after air drying;

[0076] FIG. 1B shows the material after cutting, polishing and PEG infiltration.

[0077] FIG. 2 shows an SEM image of the material surface with apatite crystals in the gelatin matrix.

[0078] FIG. 3 shows TEM images of the composite material on different scales;

[0079] FIGS. 3A and 3B show embedded hydroxyapatite needles (typical dimension approx. 1050 nm);

[0080] FIG. 3C shows embedded non-acicular hydroxyapatite particles (with sizes up to 1000 nm).

[0081] FIG. 4 shows IR spectra of the raw material (1), treated with PEG-400/water (2) or with PEG/potassium alum (3).

[0082] FIG. 5 shows X-ray powder diffractograms of the raw material (1), treated with PEG-400/water (2) or with PEG/potassium alum (3).

[0083] FIG. 6 shows the Raman data of a comparison of natural ivory (1) and the composite material (2) according to the invention.

[0084] The following examples are intended to explain the invention in greater detail, but without restricting it to the respective particular parameters and conditions.

EXAMPLE 1

Preparation of a Hydroxyapatite/Gelatin Composite Material

[0085] An aqueous gelatin solution (10 g in 75 ml deionized H.sub.2O) was added to 30 g of hydroxyapatite, suspended in 75 ml of ethanol or water, and concentrated in a beaker while agitating/stirring at approx. 50 C. The mass was then completely dried in air.

[0086] FIG. 1A shows the hydroxyapatite/gelatin composite raw material obtained as above after drying in air.

EXAMPLE 2

Preparation of a Hydroxyapatite/Gelatin Composite Material with Embedded PEG

[0087] 27 g of gelatin were introduced into 200 g of deionized water and left to stand (swell) overnight (16 hours). This mass was then heated to 55 C. in a water bath, whereby it becomes completely liquid. In a second beaker, 90 g of hydroxyapatite were suspended in 210 g of ethanol at 55 C. The aqueous gelatin solution was then slowly added to this suspension with stirring and concentrated at 55 C. for 5 hours. The white mass was poured into a plastic container, air dried for about 3 hours and was then removed from the container. The product was then further dried first in air (5 days between perforated plates) and then in an oven for 24 hours at 100 C. The material obtained can be machined.

[0088] The white product was then infiltrated first with a mixture (1:1) of PEG-400/H.sub.2O for 2 days and then with pure PEG-400 for 6 days. The ivory-colored material obtained in this way was then cut and polished accordingly.

[0089] FIG. 1B shows the material after cutting, polishing and PEG infiltration.

[0090] The process steps for the storage of PEG are independent of the raw material production and can be freely combined.

[0091] The direct infiltration of PEG-400 into still moist raw material also provided a stable product. This process variant offers the advantage of faster implementation.

EXAMPLE 3

Treatment of a Hydroxyapatite/Gelatin Composite with a Crosslinking Agent

[0092] In various process variants of the treatment with a crosslinking agent (e.g., cut/polished) hydroxyapatite/gelatin composite material was placed in a 1% aqueous potassium alum solution, a 1:1 mixture consisting of PEG-400 and 1% aqueous potassium alum solution, a 1% aqueous glyoxal solution, or a 1:1 mixture consisting of PEG-400 and 1% aqueous glyoxal solution for 2 days and then dried in air.

[0093] The process steps for crosslinking are independent of the raw material preparation or already effected infiltration and can be freely combined.

EXAMPLE 4

Preparation of Pigmented Hydroxyapatite/Gelatin Composite Materials

[0094] The respective composite material was produced analogously to Example 1 or 2. In deviation from the protocol there, either 0.3 g of solid FeCl.sub.2, 0.1 g of dioxazine violet (pigment violet 37, C.sub.40H.sub.34N.sub.6O.sub.8), 0.4 g of phthalocyanine green (heliogen green PG7, CuC.sub.32Cl.sub.16-nH.sub.nN.sub.8), 1 g of HAN-Blue (BaCuSi.sub.4O.sub.10), or 0.5 g nano-Ag (20-40 nm) were added to the hydroxyapatite suspension.

EXAMPLE 5

Preparation of a Black Hydroxyapatite/Gelatin Composite Material

[0095] 60 g of hydroxyapatite and 36 g of bone black (Kremer pigments, Germany) were suspended in 180 g of ethanol at 60 C. An aqueous gelatin solution heated to 60 C. (30 g in 230 g deionized H.sub.2O) was then added and the mixture was concentrated in a beaker with stirring at approx. 60 C. for 6 hours. The black mass was poured off and then dried completely in air. The product was then tempered at 100 C. for a further 14 hours and then processed as desired.

[0096] By pouring different colored masses together after concentrating in a mold, colored patterns/grains/inlays were also obtained.

EXAMPLE 6

Characterization of a Hydroxyapatite/Gelatin Composite Material According to the Invention

[0097] Hydroxyapatite/gelatin composite material obtained according to Example 1, 2 or 3 was characterized in more detail using various microscopic and spectroscopic examination methods.

[0098] A. Scanning Electron Microscopy (SEM)

[0099] The scanning electron microscope image was taken on a flat sample of the composite material using a DSM 982 Gemini microscope from Zeiss (Germany) in a high vacuum (secondary electron detector, 24,500 magnification, see scale).

[0100] FIG. 2 shows an SEM image of the material surface of the raw material: the apatite crystals in the gelatin matrix are visible.

[0101] B. Transmission Electron Microscopy (TEM)

[0102] The high-resolution transmission electron microscopy images were taken on a sample of the composite material that had been ultrasonically thinned out using a JEOL device ARM200F at 200 kV (JEOL Co. Ltd) equipped with a cold field emission gun and CETOR image correction (CEOS Co, Ltd.) in high vacuum. The length scale is given in the images.

[0103] FIG. 3 shows TEM images with parts of the raw material in different magnifications: Apatite crystals are visible isotropically embedded in an amorphous gelatin matrix. 3A and 3B show embedded hydroxyapatite needles (typical dimension approx. 1050 nm) and FIG. 3C shows non-needle-shaped hydroxyapatite particles with sizes up to 1000 nm.

[0104] C. Infrared Spectroscopy (IR)

[0105] The IR spectra were recorded on a flat sample of the composite material using a Perkin Elmer spectrometer BX II FT-IR from Perkin Elmer (USA) equipped with an ATR unit (Smith Detection Dura-Sample IIR diamond). The transmission spectra in the range of the wave number from 400 to 4000 cm.sup.1 have a resolution of 1 cm.sup.1 and their intensities have been scaled.

[0106] FIG. 4 shows IR spectra of the raw material (1), treated with PEG-400/water (2) or with PEG/potassium alum (3). The bands of the raw material as well as the bands of the corresponding infiltrated components are visible in all cases.

[0107] D. X-Ray Powder Diffractometry

[0108] The X-ray powder diffractograms were recorded on a flat sample of the composite material with a diffractometer in Bragg-Brentano geometry (Cu-K radiation) in reflection with a PIXcel 3D detector from PANalytical (Netherlands). The diffractograms were measured in the diffraction angle range from 10 to 90 in 2-theta and their intensities were scaled.

[0109] FIG. 5 shows X-ray powder diffractograms of the raw material (1), treated with PEG-400/water (2) or with PEG/potassium alum (3). In all cases, the reflections of the hydroxyapatite are visible as well as for sample 3 additionally those of potassium alum.

[0110] E. Raman Spectroscopy

[0111] The Raman spectra were recorded with a laser microscope Raman spectrometer (iHR 550 spectrometer; BXFM microscope) from HORIBA (Germany) with confocal geometry. The laser beam (wavelength 532 nm, power: 10 mW) was focused on a flat sample in air using an objective (100).

[0112] FIG. 6 shows the corresponding Raman data: lower curve: natural ivory (1), upper curve raw material hydroxylapatite/gelatin composite (2).

[0113] This comparison demonstrates that the Raman spectra of both materials are almost identical.

[0114] The preferred embodiments and features of the invention described in the present application can be combined with one another.

[0115] Although the invention has been described with reference to certain embodiments, it will be apparent to those skilled in the art that various changes can be made and equivalents can be used as substitutes without departing from the scope of the invention. Accordingly, the invention is not intended to be limited to the exemplary embodiments disclosed, but is intended to include all exemplary embodiments that fall within the scope of the appended claims. In particular, the invention also claims protection for the subject and the features of the subclaims independently of the claims referred to.