A biodegradable polymer as a cytokine delivery system for inducing bone formation

Bone morphogenetic proteins (BMPs) that have the potential to elicit new bo ne in vivo have been used in a tissue-engineering approach for the repair o f bone injuries and bone defects. Although it is now possible to generate l arge amounts of recombinant human (rh) BMPs for medical use, the major chal lenge remains in the development of optimal local delivery systems for thes e proteins. Here we describe the development of a synthetic biodegradable p olymer, poly-D,L-lactic acid-p-dioxanone-polyethylene glycol block copolyme r (PLA-DX-PEG). This polymer exhibits promising degradation characteristics for BMP delivery systems and good biocompatibility under test conditions. PLA-DX-PEG/rhBMP-2 composite implants induced ectopic new bone formation ef fectively when tested in vivo, and can repair large bone defects orthotopic ally. This polymeric delivery system represents an advance in the technolog y for the enhancement of bone repair.