A new growth factor controlled drug release system to promote healing of bone fractures: nanospheres of recombinant human bone morphogenetic-2 and polylactic acid.

To prepare a new drug control release system, which can markedly promote the healing of bone fractures. Optimized water-in-oil-in-water multiple emulsion evaporation method, prepared nanospheres of recombinant human bone morphogenetic-2 and polylactic acid (rhBMP-2-PLA-Ns). Its physical character was determined by the enzyme linked immunosorbent assay method. Its bioactivity was measured with the microculture tetrazolium test immunohistochemical analyses, alizarin red staining and western blot analysis. rhBMP-2-PLA-Ns exhibited an even and uniform spherical appearance without adhesion, with a particle size distribution between 35 and 65 nm, and a mean size of 45 nm. The drug loading volume and encapsulation efficiency reached ([124.73 +/- 0.41] x 10(-3))% and (90.54 +/- 1.32)%, respectively. The drug release in vitro persisted for 14 days, with a mean concentration of 73.44 +/- 5.38 ng/ml, and corresponded to the Higuichi equation (r = 0.9962). The microculture tetrazolium test showed that 4 days later, the optical density value ranking was rhBMP-2-PLA-N group > rhBMP-2 group > blank control group. Fluorescence immunocytochemical analysis showed that 10 days later the fluorescent density of the rhBMP-2-PLA-N group was significantly higher than the other two groups. Western blot analysis confirmed that the amount of vascular endothelial growth factor in the rhBMP-2-PLA-N group was the greatest. This study showed that rhBMP-2-PLA-Ns have excellent biological activity, can promote proliferation, differentiation and mineralization of osteoblasts. The drug release time is suitable for fracture healing and is an ideal delivery system for fracture healing.