Biodegradable poly(D,L-lactide) coating of implants for continuous releaseof growth factors

Local application of growth factors like insulin like growth factor-I (IGF- I) and transforming growth factor-beta 1 (TGF-beta1) from a biodegradable t hin layer of poly(D,L-lactide) (PDLLA) coated implants could stimulate frac ture healing. A new "cold coating technique" for metallic implants was esta blished to produce a biodegradable coating with a high mechanical stability that provides a continuous release of incorporated growth factors. The pro perties of this bioactive coating were investigated in vitro and in vivo. S canning electron microscope analysis revealed a coating thickness of in ave rage 14.8 mum on titanium and 10.7 mum on steel wires. Intramedullary impla ntation and extraction experiments depicted a loss of PDLLA coating from ti tanium and steel implants of less than 5%, After explantation of the implan ts, the coating displayed a complete and regular layer without any defects of PDLLA uncovering the metallic surface. Smear tests demonstrate that the coating can be performed under sterile conditions. The PDLLA depicted a red uction of about 8% within 6 weeks in vitro and in vivo. The growth factors were incorporated in a stable form and demonstrated a loss of stability of less than 3% within 42 days and less than 5% within one year. In an elution experiment, 54% IGF-I and 48% TGF-beta1 were released within the first 48 h, After 42 days, 76% of IGF-I and 71% of TGF-beta1 were detected in the el ution fluid by ELISA, Comparable results were obtained in the in vive exper iments after 42 days. (C) 2001 John Wiley & Sons, Inc.