Dense collagen membrane matrices for medical uses

A method of making a dense collagen membranous matrix material which when wetted with water is translucent and non-slippery comprising the steps of:

• a) forming an aqueous dispersion containing insoluble Type I collagen;
• b) freezing the aqueous dispersion;
• c) subjecting the frozen dispersion to freeze-drying conditions to remove frozen water and form a collagen sponge matrix;
• d) subjecting the collagen membranous matrix to humidification conditions for a time period of about 10 to about 65 minutes, such that the collagen membranous matrix absorbs about 10% to about 30% water by weight based on the weight of the collagen membranous prior to the humidification step;
• e) compressing the humidified collagen membranous matrix;
• f) cross-linking the compressed collagen matrix in either a liquid or vapor phase by treatment with a cross-linking agent selected from the group consisting of chromium sulfate, formaldehyde, glutaraldehyde, carbodiimide and adipyl dichloride, by immersing the collagen matrix in a solution of the cross-linking agent and then substantially removing the cross-linking agent;
• g) refreezing the cross-linked collagen matrix;
• h) resubjecting the frozen collagen matrix to freeze-drying conditions to remove frozen water;
• i) resubjecting the dried cross-linked collagen matrix to humidification conditions comprising a for a time period of about 5 to about 30 minutes;
• and then
• j) further compressing the humidified, collagen matrix to form the dense collagen membrane matrix material.