The osteoinductive effect of controlled BMP-2 release is location-dependent

The main challenge in BMP-2 based application lies in finding strategies that prolong its effective period, as it has a short biological half-life. Several BMP-2 release profiles have shown to enhance bone formation at various application sites. However, it remains to be determined which BMP-2 release profile best augments bone formation and whether this effect is location-dependent. Therefore, the aim of this study was to investigate the effect of BMP-2 release from oligo[(polyethylene glycol) fumarate] bis(2-(methacryloyloxy)ethyl) phosphate (OPF-BP) composites on the osteoinductive efficacy at ectopic versus orthotopic application. By varying the BMP-2 loading method, three different OPF-BP composites were created with varied release profiles. The composites were compared to unloaded OPF-BP as negative control, and to the clinically used Infuse® absorbable collagen sponge (ACS) as positive control. Bone formation was assessed by micro-computed tomography after 9 weeks of subcutaneous implantation and 3, 6, and 9 weeks of orthotopic implantation in rats (n=48). Whereas a BMP-2 burst release of >49% generated significantly more bone compared to sustained release (burst release