Dense fibrillar collagen matrices for tissue repair and the preparation method thereof

1. A method for preparing a homogeneous collagen-based material, said method comprising the following stages:

a) preparing an acid solution of pure collagen having a concentration between 0.01 and 5 mg/mL in an aqueous solvent,

b) continuously injecting the acid solution of pure collagen by controlled pressure means using a rate of injection comprised between 1 and 15 μl/min which is adapted so that the pressure force on both sides of the membrane is identical, into a dialysis cell having at least one end that is closed by a dialysis membrane with a fixed porosity, said membrane being in contact with a polymer solution in an acid medium, wherein the solvent, as well as acid and ions present in the acid solution of pure collagen, diffuse through said membrane and into the polymer solution in an acid medium, the concentration of which is adapted to the final collagen concentration,

c) optionally interrupting the injection of the acid solution of pure collagen in order to reach equilibrium or have different continuous concentration layers,

d) keeping the acid solution of pure collagen, the dialysis cell and the polymer solution in an acid medium under conditions allowing the selective mass transfer of the solvent, acid, and ions from the collagen in order to concentrate the acid solution of pure collagen and form a pure homogeneous collagen-based material having a collagen concentration of 5 to 1000 mg/ml in the dialysis cell or on the surface of the dialysis membrane, and

e) recovering the dialysis cell in which the homogeneous collagen-based material is contained or of the membrane on the surface of which the homogeneous collagen-based material is fixed, and

f) forming fibrils from the pure homogeneous collagen-based material, before or after stage e) by immersion of the collagen material under ammonia vapor.

2. The method according to claim 1 wherein the ions are mineral phase precursors selected from the group consisting of calcium and phosphate salts.

3. The method according to claim 1 , wherein the polymer is polyethylene glycol the molecular weight of which is greater than 3000 Da.

4. The method according to claim 1 wherein the fibrils are formed by treatment of the material based on homogeneous pure collagen by a gas (basic) or liquid (neutral or basic) phase.

5. The method according to claim 1 , wherein the acid solution of pure collagen used in stage a) has a collagen concentration between 0.5 and 3 mg/mL.

6. The method according to claim 1 wherein the concentration of the pure homogeneous collagen-based material obtained is 5 to 250 mg/mL.

7. A method for preparing a homogeneous collagen-based material, said method comprising the steps of:

continuously injecting using a rate of injection between 1 and 15 μl/min which is adapted so that the pressure force on both sides of the membrane is identical an acid solution of collagen comprising pure collagen, having a concentration between 0.01 and 5 mg/mL acid and an aqueous solvent into a dialysis cell, the dialysis cell comprising at least one membrane surface in contact with a polymer solution comprising a polymer in an acid medium, the at least one membrane surface having a porosity sized to prevent diffusion,

optionally interrupting the injection of the acid solution of pure collagen in order to reach equilibrium or have different continuous concentration layers, of the pure collagen and the polymer across the at least one membrane surface,

maintaining the polymer solution at an osmotic pressure greater than an osmotic pressure of the acid solution of collagen to promote diffusion of the acid and aqueous solvent through the at least one membrane surface into the polymer solution to form, within the dialysis cell, a homogeneous pure collagen-based material having a collagen concentration of 5 to 1000 mg/ml, and

recovering the homogeneous pure collagen-based material having a collagen concentration of 5 to 1000 mg/ml from the dialysis cell, and

forming fibrils in the homogeneous pure collagen-based material having a collagen concentration of 5 to 1000 mg/ml before or after said material is recovered from the dialysis cell by immersion of the collagen material under ammonia vapor.

8. The method according to claim 7 , wherein the acid solution of collagen further comprises mineral phase precursors selected from the group consisting of calcium and phosphate salts, and the mineral phase precursors diffuse through the at least one membrane surface into the polymer solution.