Adhesion-Preventive Biomaterials

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Postoperative adhesion of tissues sometimes cause severe problems. Therefore, several techniques have been attempted to prevent tissue adhesion, for instance, by applying viscous aqueous solutions of polymer to protect the tissue. Our method is to insert a bioabsorbable sheet between the tissues where adhesion will possibly take place. For this purpose, a soft, flexible sheet was prepared from a copolymer of D,L-lactide and <epsilon> -caprolactone. The caprolactone monomer was copolymerized so as to reduce the softening temperature of the sheet. The biodegradation rate of the sheet is important in addition to the flexibility. L-Lactide-caprolactone copolymers of 65:35 and 88:12 (by mole) showed 100 % weight loss after 20 and 24 weeks, respectively, when immersed in PBS at 37 C. To examine the effectiveness of our bioabsorbable sheet in vivo, the pericardium and the parietal pleura of the same dog was partially ablated and the bioabsorbable sheet (D,L-lactide-caprolactone 80:20, copolymer) with a size of 4 x 8 <cm^2> was fixed in between. Inspection at 3rd month postoperation revealed no inflammation and no symptom of adhesion of the surrounding tissues. Also, a study was undertaken to examine the possibility of prevention of the scar formation after lumbar laminectomy by use of poly-D,L-lactide sheet containing elastase that would prevent the growth of collagen fibrils. Experiments on rabbits showed that the sheet containing elastase more effectively suppressed the scar formation than the sheet without elastase.