GALATIK ANTONIN (CZ)
| WO1999047188A1 | 1999-09-23 |
| US20020013627A1 | 2002-01-31 |
P A T E N T C L A I M S
1. Procedure for the manufacture of a structured multilayer membrane applicable to surgical reconstruction of dental, bone, cartilage, or ligament tissue, the membrane consisting of a minimum of one closed structural layer - barrier - and/or one porous open layer, characterized in that a collagen suspension accommodated in a flat bed is frozen into plates, which are then vacuum-dried at a temperature lower than their freezing temperature, and the sponge-like membranes are wetted by controlled application of a limited amount of water which is less than sufficient for the hydration of the whole membrane thickness, and the wetted membrane is conveniently allowed to rest at a reduced temperature of 0 0 C to 10° C for the moisture to equilibrate inside the structure, mechanical pressure is applied in order to modify the thickness of the plate as appropriate, one side is conveniently discriminated from the other by applying a tread pattern or dye, the plate is re-frozen and dried at a reduced pressure, the drying procedure being such that at a later stage the temperature of the material is increased to above the thawing temperature in a controlled manner, whereby a closed structure is attained by drying in that part of the membrane which is still wet.
2. Procedure under Claim 1 characterized in that the collagen is collagen I and is obtained from animal tissue by purification.
3. Procedure under Claim 1 or Claim 2 characterized in that the collagen is freed from telopeptides, partly at least.
4. Procedure under Claims 1 to 3 characterized in that the collagen is cross-linked and contains glycosaminoglycan bonded by metallo-complex bonding.
5. Procedure under any of Claims 1 to 3 characterized in that the sponge-like membrane is impregnated with chondrocytes during the wetting step.
6. Procedure under any of Claims 1 to 4 characterized in that the sponge-like membrane is impregnated with glycosaminoglycan during the wetting step.
7. Procedure under any of Claims 1 to 6 characterized in that it involves chondronectin, laminin, fibronectin, calcium alginate, anchorin, bacteriostatics, pharmacologically active substances, growth factors and/or morphogenetic bone factors.
8. A multistructural layered membrane manufactured by a procedure under any of Claims 1 to 7.
9. The use of a multistructural layered membrane under Claim 8 in the manufacture of implants, promoting guided tissue and/or bone regeneration. |
Procedure for the manufacture of a structured multilayer membrane, the structured multilayer membrane and its uses
Scope of technology
The invention is a procedure for the manufacture of a structured multilayer membrane for controlled cartilage, tissue or bone regeneration or repair in vivo.
Present status of technology
It is now generally accepted that reconstruction of tissue requires the provision of a matrix to serve as a guide orienting and, on the other hand, limiting the direction of cell growth during the healing process. In a procedure described in international patent application WO-A-96/25961 , a structurally homogeneous single-layer matrix consisting of natural membranes formed by collagen Il is used. Such membranes, however, fail to regenerate cartilage tissues to a sufficient extent. Therefore, a multilayer membrane consisting of a membrane made of collagen Il and connected by sewing to another layer consisting of a porous matrix made of collagen I and allowing cell ingrowth, was devised as described in patent application WO-A-96/24310. A next improvement was brought about by a procedure described by patent application WO 1999/019005, where instead of by sewing, a reasonably strong bonding between the layers is achieved through adhesion of the collagen gel, which can be enhanced by the effect of chemical or physico-chemical cross-linking. In order to reduce pyrogenicity of the collagen implants, CS 297 205 patent describes a procedure using atelocollagen, a modification of collagen from which the terminal telopeptides containing antigenic determinants have been removed (partly at least). An extension of the time of membrane absorption, accompanied by a controlled release of pharmaceutically active components (if present) via metallo-complex networking and collagen grafting with hyaluronan is the core of a procedure described by Czech patent application PV 2006-409.
We found that cartilage and/or bone tissue can be also reconstructed by using single-component membranes whose structure comprises horizontally arranged layers with different material densities. The density of a layer is determined by the number and size of pores or capillary channels they contain. While a layer possessing a dense structure acts as a barrier preventing the penetration of chondrocytes and other cells, another membrane layer possesses an open and porous structure allowing cell ingrowth. The transition between the two structures can be smooth, without any sharp boundary between them.
Subject of the invention
The invention provides a procedure for the manufacture of a structured multilayer membrane, well suited to tissue, cartilage or bone reconstruction, that (i) consists of one collagen type, conveniently collagen I, from which telopeptides have been removed (partly at least) and which can be cross-linked
and can contain pharmacologically active substances, particularly glycosaminoglycans, (ii) contains at least one structural layer closed to cell ingrowth, and (iii) contains at least one porous structural layer open to cell ingrowth. The procedure consists of steps where a homogeneous porous membrane is created by freeze-drying of plates of frozen collagen gel and the membrane is then wetted by controlled application of a mixture of water and additives, if any, to one or both surfaces and the material is allowed to hydrate for a period of time, conveniently at a reduced temperature. The thickness of the wetted membranes is then modified as appropriate by application of pressure, and the structure obtained is stabilized by rapid freezing. A non-porous structure of the membrane layer is formed during a process where final drying is conducted at a reduced pressure, the temperature of the plates being allowed to increase to above the freezing point within a pre-tested phase. The thickness and density of the non-porous structure in the membranes can be controlled by varying the length of the period of drying at temperatures above the freezing point and the total water content of the membrane.
Membranes so prepared are not prone to decomposition into the layers during the healing process and exhibit improved apyrogenicity, owing to the fact that a collagen type - conveniently atelocollagen modified by lowering of its telopeptide content - is used, whereby the total amount of antigenic determinants in the implanted membranes is reduced.
A membrane so prepared constitutes a suitable medium for the ingrowth of natural chondrocytes and thus to the regeneration of the cartilage. The recovery process can be additionally promoted by impregnating the membrane with chondrocytes or other pharmacologically active substances, either prior to its implantation or after implantation, by the injection route.
The membrane collagen material can conveniently consist of pure non-denatured and insoluble collagen and can be prepared, for instance, by procedures described in patent document CS 276 891 or in Czech patent application PV 2006-409.
Examples of application of the invention
Example 1
Connective tissue of bovine tendons from young cattle is mechanically freed from fat and from the connective tissue capsule, ground, rinsed under running water, and extracted triply with a 10% sodium chloride solution for 24 hours and then at least triply with a half-saturated solution of calcium hydroxide for 24 hours until its non-collagen protein content has decreased to below 1%. Subsequently, the material is neutralized with acetic acid, washed with water, dehydrated with ethanol, and freed from residual fat by extraction with benzine. The resulting fibrous material is dispersed in demineralized water, freed from telopeptides by an enzymatic process, washed with demineralized water, and dissolved by acidification to pH 3,5. A gel-like suspension containing 10 g of atelocollagen in a litre is
thus obtained. A homogeneous porous membrane is then formed by freeze-drying of collagen gel plates obtained by freezing in flat beds at -15°C. The membrane is wetted by controlled application of water to one or both surfaces so that the amount of water does not exceed 20% of the membrane weight, and the material is allowed to hydrate at 0 0 C to 5°C for 5 hours. Pressure is applied to a compression plate to attain a suitable thickness of the wet membranes, usually between 3 mm and 0.1 mm, and the structure achieved is stabilized by rapid freezing. The frozen membranes are dried at a reduced pressure to the final state, the temperature of the plates being allowed to increase to 3°C - 5°C during a pre-tested phase.
Example 2
A membrane is prepared as in Example 1, only an aqueous solution containing 0.15% hyaluronan, 0,001% magnesium chloride, and 5 mg/l joint cartilage chondrocytes is used in place of water in the wetting step. The ensuing procedure is identical with that described in Example 1.