IN-VITRO DEGRADATION AND RELEASE CHARACTERISTICS OF BIODEGRADABLE IMPLANTS CONTAINING TRYPSIN-INHIBITOR

The use of a biodegradable implant system that provides a steady, cont rolled release of drugs or bioactive factors can be an attractive deli very vehicle of substances that can enhance repair processes in the mu sculoskeletal system. The present in vitro study examined the degradat ive characteristics and release kinetics of a 50 to 50 polylactic acid /polyglycolic acid implant, used as a carrier of trypsin inhibitor, du ring a 10-week period. Morphological and scanning electron microscopic examinations demonstrated that the implant degraded in a gradual, ext ended fashion such that by 10 weeks the implant was completely dissolv ed. It also was shown that the protein was released from the implant i n a sigmoidal fashion with increased release between 3 and 7 weeks. Mo re than 95% of the trypsin inhibitor originally incorporated in the im plants was released during the 10-week test period. To describe furthe r the degradation process of the implant, temporal changes in its mole cular weight and surface axial strain were determined also. It was sho wn that in the initial 4 weeks, there was a marked decrease in molecul ar weight of the implants. Axial strain decreased and then increased o ver time, suggesting an initial period of stiffening followed by a per iod of degradative softening.