POROUS-COATED TITANIUM IMPLANT IMPREGNATED WITH A BIODEGRADABLE PROTEIN DELIVERY SYSTEM

Tissue ingrowth into porous-coated orthopedic and dental implants is c ommonly used as a means to achieve long-term fixation of these prosthe ses. However, the degree of tissue ingrowth is often inadequate and in consistent. if the pores of these implants are impregnated with a cont rolled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present stud y introduces such a system based on biodegradable polymers and investi gates its protein release profile and polymer degradation characterist ics. Porous coated titanium implants were impregnated with a mixture o f a 50%-50% polylactic acid-polyglycolic acid copolymer and a model pr otein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degr adation in phosphate buffered saline at 37 degrees C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weigh t of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant di fference in the polymer degradation characteristics between the contro l and test implants, which might be the result of some complex polymer -protein interactions. (C) 1997 John Wiley & Sons, Inc.