Morphological and histological analysis on the in vivo degradation of poly (propylene fumarate)/(calcium sulfate/β-tricalcium phosphate)

Poly (propylene fumarate)/(Calcium sulfate/β-tricalcium phosphate) (PPF/(CaSO₄/β-TCP)) is a kind of biodegradable composite designed for bone tissue engineering. The in vitro degradation behavior of this composite has been investigated in our previous study. The aim of this study was to investigate the effects of PPF molecular weight and CaSO₄/β- TCP molar ratio on the in vivo degradation of PPF/(CaSO₄/β-TCP) composite and the bone tissue response to PPF/(CaSO₄/β-TCP). Total 36 PPF/(CaSO₄/β-TCP) composite samples were implanted into 15.0 mm segmental defects in tibiae of 18 Japanese rabbits, harvested at 2, 4 and 8 weeks after the operation, and analyzed using radiographic and histological analysis to assess the in vivo degradation of the composites as well as tissue response to the implants. The in vivo degradation results show that all the samples maintained their original shape. Tissues penetrated into the pores which formed by the degradation of CaSO₄/β-TCP spheres near the surface of the composites. The rate of in vivo degradation and pore forming increased with a decrease in PPF molecular weight and an increase in CaSO₄/β-TCP molar ratio. No inflammatory reaction was observed after implantation, and the composites are capable of in situ pore forming. In particular, the pore forming rate can be adjusted by varying the composition of the composites. These results may indicate that PPF/(CaSO₄/β- TCP) is a promising osteogenic scaffold for its controllable degradation rate and excellent biocompatibility.