Novel injectable porous poly(γ-benzyl-L-glutamate) microspheres for cartilage tissue engineering: preparation and evaluation

In search of an injectable cellular delivery vehicle for tissue regeneration, porous microspheres fabricated from the synthetic polypeptide of poly(gamma-benzyl-L-glutamate) (PBLG) were developed. The structural and morphological characteristics of the microspheres could be adjusted by changing the amounts of the gelatin porogen. PBLG microspheres fabricated from 6.5% gelatin content exhibited an average pore diameter of 50.9 +/- 10.3 mu m and a porosity of 86.58 +/- 2.37%. Degradation in vitro of the microspheres could be well controlled by adjusting the molecular weight of PBLG, and the degradability in vivo showed a satisfactory degradation time range from 8 to 12 weeks. Articular chondrocytes, which were seeded within the PBLG porous microspheres, exhibited progressive proliferation and deposition of the cartilaginous extracellular matrix. After cultivation for 2 days in vitro, the PBLG porous microspheres loaded with chondrocytes were injected subcutaneously into nude mice. At 4, 8 and 12 weeks postinjection, neo-generated tissue was harvested for histological observations, which showed a typical cartilage structure and cartilaginous matrix accumulation. A gradual increase of GAG and COL II content in neo-generated tissue was detected by biochemical analysis. These results indicate that the fabricated porous microspheres showing controllable degradation properties, good biocompatibility and cytocompatibility are potentially useful as an injectable vehicle for cartilage tissue engineering.