Method for preparing neutralized matrix of non-antigenic collagenous material

Abstract

The present invention relates to a method for preparing a neutralized matrix of non-antigenic collagenous material comprising the steps of: a) preparing an acidic solution of non-antigenic collagenous material, b) pouring the solution of a) into a mold in order to form a layer, c) lyophilizing the layer of b) in order to obtain an acidic matrix of non-antigenic collagenous material, d) sterilizing the acidic matrix obtained in c) with ethylene oxide in order to obtain a neutralized matrix of non-antigenic collagenous material. The invention also relates to the matrices obtained and to surgical implants comprising such matrices.

Claims

1. A method for preparing a neutralized matrix of non-antigenic collagenous material comprising: a) preparing an acidic solution of non-antigenic collagenous material, wherein a pH of said acidic solution is adjusted to a value ranging from about 2.0 to about 4.0, b) pouring said acidic solution of a) into a mold in order to form a layer, c) lyophilizing said layer of b) in order to obtain an acidic matrix of non-antigenic collagenous material, d) sterilizing said acidic matrix obtained in c) with ethylene oxide in order to obtain a neutralized matrix of non-antigenic collagenous material.

2. The method according to claim 1, wherein said acidic solution of step a) is a solution of non-antigenic collagenous material in acidic water, said non-antigenic collagenous material concentration in said acidic solution ranging from 0.1 to 10% by weight, relative to a total weight of said acidic solution.

3. The method according to claim 2, wherein said non-antigenic collagenous material concentration in said acidic solution ranges from 0.5% to 3% by weight, relative to a total weight of said acidic solution.

4. The method according to claim 2, wherein said non-antigenic collagenous material concentration in said acidic solution is 1% by weight, relative to a total weight of said acidic solution.

5. The method according to claim 1, wherein said pH of said acidic solution in a) is adjusted to a value ranging from about 3.0 to about 3.5.

6. The method according to claim 1, wherein said pH of said acidic solution in a) is adjusted to a value of about 3.4.

7. The method according to claim 1, further comprising adding chlorohydric or acetic acid to said acidic solution of step a).

8. The method according to claim 1, wherein said acidic solution of step a) is free of any other polymer than the non-antigenic collagenous material.

9. The method according to claim 1, wherein said lyophilizing of said layer in c) comprises freezing said layer during a time ranging from 3 to 15 hours to form a frozen layer.

10. The method according to claim 9, wherein said frozen layer is primarily dried during a time ranging from 7 to 15 hours.

11. The method according to claim 1, wherein said sterilizing the acidic matrix in d) comprises exposing said acidic matrix to ethylene oxide for a time ranging from about 10 to about 11 hours.

12. The method according to claim 1, wherein said ethylene oxide is injected at a pressure ranging from 70000 Pa to 78000 Pa.

13. A surgical implant comprising at least one neutralized matrix of non-antigenic collagenous material obtained by the method of claim 1.

14. The surgical implant according to claim 13, wherein the at least one neutralized matrix of non-antigenic collagenous material comprises a tensile strength at least two times greater than that of a non-sterilized matrix of non-antigenic collagenous material.

15. The surgical implant according to claim 14, wherein said tensile strength is about three times greater than that of a non-sterilized matrix of non-antigenic collagenous material.

16. The surgical implant according to claim 13, wherein the surgical implant is a hernia repair implant.

17. The surgical implant according to claim 13, wherein the surgical implant is a haemostat.

18. The surgical implant according to claim 13, wherein the at least one neutralized matrix of non-antigenic collagenous material comprises a tensile strength of 0.5 N.

Description

(1) The invention and the advantages thereof will emerge more clearly from the example below and the appended FIGURE in which:

(2) FIG. 1 is a graph comparing the tensile strengths of a matrix obtained with the method of the invention and of two other matrices not obtained with the method of the invention.

EXAMPLE 1

(3) Non-antigenic collagenous material, similar to that described at example 5 of U.S. Pat. No. 6,936,271, except for the crosslinking step, is provided, under the form of powder.

(4) A solution of non-antigenic collagenous material at 1% (w/w) in water is prepared and adjusted to about pH 4.0 by addition of HCl.

(5) 121 g of this solution is poured into a rectangular mould of dimensions of 12 cm17 cm, so as to form a layer of the solution.

(6) The layer is lyophilised for about 24 hours, with a freezing step of 4 hours, and a primary drying step of 8 hours.

(7) A matrix of non-antigenic collagenous material is obtained. This matrix is acidic, i.e. this matrix has an extractible pH of about 5.2.

(8) The matrix is then sterilized with ethylene oxide according to the following process.

(9) In a first stage, the matrix is put in a cell and is exposed during 8-15 hours to a warm and humid environment with the following parameters: Temperature: 28-32 C. Relative humidity: 50-80%

(10) In a second stage, the cell is evacuated and the ethylene oxide is introduced. The matrix is exposed to ethylene oxide for approximately 10-11 hours. During this time, 1.6 to 2 kg of ethylene oxide is injected. The ethylene oxide injection pressure ranges from 70000 to 78000 Pa. The temperature and relative humidity are the same as in the first stage.

(11) In a third stage, ethylene oxide is removed.

(12) The sterilized matrix obtained shows an extractible pH of about 7.0. As a consequence, the sterilization of the matrix with ethylene oxide has led to an increase of the extractible pH of the matrix from about 5.2 to about 7.0.

(13) The sterilized matrix of non-antigenic collagenous material is therefore neutralized. Such a matrix may be used for the manufacture of a surgical implant such as an abdominal reinforcement or a haemostatic patch with no risk that the matrix dissolves or collapses at the contact of a neutral medium such as the biological fluid.

(14) In addition, the sterilized and neutralized matrix obtained shows very good tensile strength. In particular, the sterilized matrix shows a higher tensile strength than the non sterilized matrix.

(15) Comparative Tests:

(16) The tensile strengths of the matrix of the present example before sterilization (comparative referenced N/A), after sterilization with ethylene oxide (invention referenced EtO), and of a matrix of same composition of that of the present example but neutralized with ammonia (comparative reference Ammonia) have been measured according to the test described in standard ASTM D0638-03 with type IV specimen.

(17) With reference to FIG. 1, are shown: the tensile strength of the matrix of the present example before sterilization (reference N/A on the graph), the tensile strength of the matrix of the present example after sterilization with ethylene oxide (referenced EtO on the graph), and the tensile strength of a matrix of same composition of that of the present example but neutralized with ammonia (referenced Ammonia).

(18) The results are collected in the following table:

(19) TABLE-US-00001 N/A Ammonia Sample (comparative) EtO (invention) (comparative) Tensile strength 0.15 0.50 0.28 in Newton

(20) As shown on this graph, the tensile strength of the matrix obtained by the method of the invention is at least two times, and is even about three times, greater than that of the non sterilized matrix. In addition, the tensile strength of the matrix obtained by the method of the invention is about twice greater than that of a matrix neutralized by Ammonia.

EXAMPLE 2

(21) Non-antigenic collagenous material, similar to that described at example 5 of U.S. Pat. No. 6,936,271, except for the crosslinking step, is provided, under the form of powder.

(22) A solution of non-antigenic collagenous material at 1% (w/w) in water is prepared and adjusted to about pH 3.4 by addition of CH.sub.3COOH.

(23) 121 g of this solution is poured into a rectangular mould of dimensions of 12 cm17 cm, so as to form a layer of the solution.

(24) The layer is lyophilised for about 24 hours, with a freezing step of 4 hours, and a primary drying step of 8 hours.

(25) A matrix of non-antigenic collagenous material is obtained. This matrix is acidic, i.e. this matrix has an extractible pH of about 5.1.

(26) The matrix is then sterilized with ethylene oxide according to the following process.

(27) In a first stage, the matrix is put in a cell and is exposed during 8-15 hours to a warm and humid environment with the following parameters: Temperature: 28-32 C. Relative humidity: 50-80%

(28) In a second stage, the cell is evacuated and the ethylene oxide is introduced. The matrix is exposed to ethylene oxide for approximately 10-11 hours. During this time, 1.6 to 2 kg of ethylene oxide is injected. The ethylene oxide injection pressure ranges from 70000 to 78000 Pa. The temperature and relative humidity are the same as in the first stage.

(29) In a third stage, ethylene oxide is removed.

(30) The sterilized matrix obtained shows an extractible pH of about 7.0-7.4. As a consequence, the sterilization of the matrix with ethylene oxide has led to an increase of the extractible pH of the matrix from about 5.1 to about 7.0-7.4.

(31) The sterilized matrix of non-antigenic collagenous material is therefore neutralized. Such a matrix may be used for the manufacture of a surgical implant such as an abdominal reinforcement or a haemostatic patch with no risk that the matrix dissolves or collapses at the contact of a neutral medium such as the biological fluid.

(32) The tensile strengths of the matrix of the present example before sterilization and after sterilization with ethylene oxide have been measured according to the test described in standard ASTM D0638-03 with type IV specimen.

(33) The results are collected in the following table:

(34) TABLE-US-00002 Matrix (before Matrix (after EtO Sample sterilization) sterilization) Tensile strength 0.28 0.78 in Newton

(35) As shown on this graph, the tensile strength of the matrix obtained by the method of the invention is at least twice, and is even about 2.8 times, greater than that of the non sterilized matrix.