Silicic acid condensates having a low degree of cross-linking in a polymer matrix

Abstract

A material or biomaterial comprising silicic acid condensates having a low degree of cross-linking, and methods for its production are subject-matter of the invention. A method for the production of silicic acid structures having a low degree of cross-linking is disclosed, wherein a sol is produced, wherein further condensation is prevented when specific cross-linking of the silicic acid is reached, wherein, preferably, structures having a size of 0.5-1000 nm are produced, e.g. polyhedral structures or aggregates of the same. Further condensation can be prevented by means of mixing with a polymer. In one embodiment, this comprises nano-structured, silicon dioxide (SiO.sub.2) having a low degree of cross-linking that is embedded in a polymer matrix. The material can be used in medicine for therapeutic purposes, and can enter into direct contact with biological tissue of the body in this connection. This material herein enters into chemical, physical, and biological interactions with the corresponding biological systems. It can herein be decomposed, and can act as a supplier for the silicic acid required for metabolism. Furthermore, it can have a supportive or shielding effect. It can be present as a granulate, microparticles, fiber, and as a woven or nonwoven fabric produced therefrom, or as a layer on implants or wound dressings. The material can be used as a medical device or as a nutritional supplement.

Claims

1. A biomaterial, composed of SiO.sub.2 structures having a low degree of cross-linking, wherein said SiO.sub.2 structures have a size of 0.5 nm to 1000 nm, and are distributed in a polymer matrix, wherein SiO.sub.2 and polymer are present in a mass ratio of 0.5/99.5 (SiO.sub.2/polymer) up to 50/50, but not including 50/50, wherein the polymer is polyvinylpyrrolidone.

2. The biomaterial according to claim 1, wherein said biomaterial is a hydrogel composed of SiO.sub.2 polyhedral structures having a size of 0.5 nm to 4 nm, and a water-soluble polymer, wherein polymer and SiO.sub.2 polyhedral structures are homogeneously distributed.

3. The biomaterial according to claim 1, wherein said biomaterial is present as threads, as a film, or as a sponge.

4. The biomaterial according to claim 1, which, together with granulates that can be used as bone replacement material, forms a mass for filling of bone defects (putty).

5. The biomaterial according to claim 1, for use as a medical device having a supporting or shielding function.

6. The biomaterial according to claim 1, for use for the treatment of wounds or scars or for cosmetic applications.

7. The biomaterial according to claim 1, wherein the biomaterial is made by a method for the production of silicic acid structures having a low degree of cross-linking in a polymer matrix, comprising: a) producing a SiO.sub.2 sol in a solvent, wherein the sol particles have a size of 0.5 nm to 1000 nm, b) producing a solution of a polymer in a solvent, c) mixing the solution and the sol homogeneously, wherein SiO.sub.2 and polymer are present in a mass ratio of 0.5/99.5 (SiO.sub.2/polymer) up to 50/50, but not including 50/50.

8. A medical device or a nutritional supplement comprising the biomaterial according to claim 1.

9. A method for the production of a formable bone replacement material (putty), comprising a) moistening a granulate that can be used as a bone replacement material with an aqueous solution, and b) mixing the granulate that can be used as bone replacement material with a biomaterial according to claim 1.

10. The method according to claim 9, wherein the granulate that can be used as a bone replacement material comprises porous material.

11. The method according to claim 9, wherein the granulate that can be used as a bone replacement material comprises a calcium phosphate.

12. The method according to claim 9, wherein the granulate that can be used as a bone replacement material is of bovine origin.

13. The method according to claim 9, wherein the granulate that can be used as a bone replacement material comprises hydroxyl apatite ceramic.

14. The method according to claim 9, comprising freeze-drying the formable bone replacement material (putty).

15. The method according to claim 9, comprising subjecting the formable bone replacement material (putty) to gamma irradiation.

16. A formable bone replacement material (putty), comprising a granulate that can be used as a bone replacement material and a biomaterial according to claim 1.

17. The biomaterial according to claim 5, wherein said polyvinylpyrrolidone is polyvinylpyrrolidone K90.

18. The biomaterial according to claim 3, wherein said threads form a nonwoven or woven fabric.

19. The method according to claim 15, wherein the formable bone replacement material is subjected to gamma irradiation at 25-40 kGray.

Description

FIGURE LEGENDS

(1) The FIGURE shows, in various enlargements, scanning electron microscopy images of the sponge produced in Example 1 from polyvinylpyrrolidone and SiO.sub.2 nanoparticles. A: scale=200 m, B: scale=40 m, C: scale=9 m.

EXAMPLES

Example 1

(2) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 6% SiO.sub.2 content is formed. 200 g of this sol are homogeneously mixed with 200 g of a twelve-percent PVP solution. For this purpose, ultrasound homogenization is used. Subsequently, the pH is adjusted to 7.4 with NaOH solution. The gel is placed in molds, for example with a size of 100 mm100 mm8 mm, and freeze-dried. Scanning electron microscopy images are shown in FIG. 1.

Example 2

(3) Water-Soluble Nonwoven Fabric for Covering Wounds

(4) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 0.66% SiO.sub.2 content is formed. 200 g of this sol are homogeneously mixed with 200 g of an aqueous 1.34% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. The gel is placed in molds with, for example, a size of 100 mm100 mm8 mm, and freeze-dried. A nonwoven fabric for wound covering is formed.

Example 3

(5) Water-Insoluble Nonwoven Fabric for Wound Covering

(6) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 0.66% SiO.sub.2 content is formed. 200 g of this sol are homogeneously mixed with 200 g of an aqueous 1.34% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. The gel is placed in molds with, for example, a size of 100 mm100 mm8 mm, and freeze-dried. Afterward, the nonwoven fabric that has formed is exposed to saturated steam until it has absorbed 10% of its weight in water (swelling). Subsequent gamma irradiation (25-40 KGray) ensures cross-linking of the PVP in the nonwoven fabric. A nonwoven fabric for wound covering is formed.

Example 4

(7) Gel-Like Wound Covering

(8) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 6% SiO.sub.2 content is formed. 200 g of this sol are homogeneously mixed with 200 g of an aqueous 12% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. The gel is placed in molds with, for example, a size of 100 mm100 mm8 mm, and subjected to gamma irradiation of 25-40 kGray. A gel-like moist wound covering is formed.

Example 5

(9) Bone Replacement Material Putty

(10) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 6% SiO.sub.2 content is formed. 50 g of this sol are homogeneously mixed with 50 g of an aqueous 12% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. 62 g of a highly porous bone replacement material granulate (produced according to patent EP 1 624 904) are mixed with as much water that the internal pores are filled (in this case with 44 g water). The silica/PVP mixture and the moist granulate are homogeneously mixed. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. The mass is filled into typical applicators for bone replacement and sterilized in an autoclave.

Example 6

(11) Bone Replacement Material Putty for Mixing with Commercially Available Antibiotic Solutions

(12) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 6% SiO.sub.2 content is formed. 50 g of this sol are homogeneously mixed with 50 g of an aqueous 12% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. 62 g of a highly porous bone replacement material granulate (produced as described in European Patent EP 1 624 904) are mixed with as much water that the internal pores are filled (in this case with 44 g water). The silica/PVP mixture and the moist granulate are homogeneously mixed. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. Cylinders are formed from the mass (10 mm diameter, 30 mm length). These cylinders are freeze-dried. Sponge-like dry elements are formed, which are introduced into applicators having an inside diameter of 10 mm. Steam-tight packaging in commercially available aluminum peel bags and gamma sterilization take place subsequently. For use, as much antibiotic solution is added to the sponge-like elements in the applicator that there is no air in the applicator (e.g. 1.5 ml Gentamicin-ratiopharm 40 SF injection solution). The sponge-like cylinder swells and yields a kneadable mass (putty) for filling of bone defects.

Example 7

(13) Elastic Molded Element of Bone Replacement Material

(14) With a cation exchanger (e.g. LEWATIT), the sodium ions are removed from sodium silicate solution having a SiO.sub.2 content of 7%. A sol with a pH of approximately 2.4 is formed. After a determination of the content of solids, water is added until a sol having a 6% SiO.sub.2 content is formed. 50 g of this sol are homogeneously mixed with 50 g of an aqueous 12% PVP K 90 solution (PVPpolyvinylpyrrolidone). For mixing, a stirrer is used at 1000 rpm. 62 g of a highly porous bone replacement material granulate (produced as described in European Patent EP 1 624 904) are mixed with as much water that the internal pores are filled (in this case with 44 g water). The silica/PVP mixture and the moist granulate are homogeneously mixed. Subsequently, the pH is adjusted to 7.40.5 with NaOH solution. The mass is placed into molds (blister packs 15105 mm.sup.3). Steam-tight packaging in commercially available aluminum peel bags and gamma sterilization at preferably 25-40 kGray follow. Elastic blocks that are used for bone augmentation form.