A novel surgical material made from collagen with high mechanical strength: a collagen sandwich membrane.

We have developed a novel collagen membrane with excellent mechanical properties using a new method and examined its breaking strength, microstructure, and absorption behavior in vivo. Types I and III atelopeptide collagen extracted from porcine skin by treatment with pepsin were used. One volume percent collagen hydrochloride solution, pH 3.0, was frozen in a cast, then freeze-dried and pressed. Both surfaces of the resulting membrane were coated with 2% w/v collagen hydrochloride solution, pH 3.0, and dried. This procedure was then repeated 10 times, and the membrane was finally heated in vacuo. Microstructural observation showed that the inner part of the membrane consisted of piles of thin collagen nonwoven fabric layers, whereas the coated surface consisted of an amorphous collagen layer. The breaking strength of this membrane with a thickness of 0.5 mm was 73.5 N/cm in dry conditions. The mechanical strength of the membrane was 3.4 to 10.8 times greater than that of control membranes that had not been subjected to coating procedures. The absorption of this membrane was investigated by an implantation test in rabbits. The absorption rate of the membrane in vivo was similar to that of the noncoated control material, and only minimal tissue reaction was evident. Because the mechanical properties of this membrane, made from only collagen, are adequate for suturing without reinforcement by other materials, and its absorption in vivo has so far been equal to that of collagen membranes, the membrane is potentially applicable for various surgical uses such as replacement of tissue defects.