Release characteristics and osteogenic activity of recombinant human bone morphogenetic protein-2 grafted to novel self-assembled poly(lactide-co-glycolide fumarate) nanoparticles.

Functionalized biodegradable nanoparticles (NPs) provide reactive groups and large surface area for grafting Recombinant human bone morphogenetic protein-2 (rhBMP-2) to reduce protein diffusion and maintain sufficient concentration for recruitment and differentiation of osteoprogenitor cells. The objective of this work was to investigate release characteristics and osteogenic activity of rhBMP-2, grafted to biodegradable NPs based on succinimide-terminated poly(lactide fumarate) (PLAF-NHS) and poly(lactide-co-glycolide fumarate) (PLGF-NHS) macromers. The release of rhBMP-2 from the NPs, measured by enzyme-linked immunosorbent assay, was linear with time in the first two weeks, and 24.70±1.30% and 48.7±0.7% of the protein grafted to PLGF-NHS and PLAF-NHS NPs, respectively, was released in the enzymatically active conformation after complete degradation/erosion of the NPs. After 14 days of incubation with bone marrow stromal (BMS) cells, rhBMP-2 grafted to PLAF-NHS and PLGF-NHS NPs was as effective in inducing mineralization as the native rhBMP-2 that was directly added to the cell culture media. At any incubation time, rhBMP-2 grafted to PLAF had the highest expression of osteopontin (OP) and osteocalcin (OC), followed by rhBMP-2 grafted to PLGF and rhBMP-2 directly added to media. Higher OP and OC expression for BMP-gPLAF and BMP-gPLGF groups may be related to other factors in the cascade of osteogenesis, such as differentiation of BMS cells to the vasculogenic lineage and formation of a vascularized/mineralized marix.

功能化的可生物降解纳米粒子（NPs）为接枝重组人骨形态发生蛋白 - 2（rhBMP - 2）提供了反应基团和较大的表面积，以减少蛋白质扩散并维持足够浓度，用于招募和分化骨祖细胞。本研究的目的是探究接枝到基于琥珀酰亚胺封端的聚（富马酸丙交酯）（PLAF - NHS）和聚（富马酸丙交酯 - 共 - 乙交酯）（PLGF - NHS）大分子单体的可生物降解纳米粒子上的rhBMP - 2的释放特性和成骨活性。通过酶联免疫吸附测定法测量，rhBMP - 2从纳米粒子中的释放在前两周与时间呈线性关系，在纳米粒子完全降解/侵蚀后，接枝到PLGF - NHS和PLAF - NHS纳米粒子上的蛋白质分别有24.70±1.30%和48.7±0.7%以具有酶活性的构象释放。在与骨髓基质（BMS）细胞孵育14天后，接枝到PLAF - NHS和PLGF - NHS纳米粒子上的rhBMP - 2在诱导矿化方面与直接添加到细胞培养基中的天然rhBMP - 2一样有效。在任何孵育时间，接枝到PLAF上的rhBMP - 2的骨桥蛋白（OP）和骨钙素（OC）表达最高，其次是接枝到PLGF上的rhBMP - 2和直接添加到培养基中的rhBMP - 2。BMP - gPLAF和BMP - gPLGF组较高的OP和OC表达可能与骨生成级联中的其他因素有关，例如BMS细胞向血管生成谱系的分化以及血管化/矿化基质的形成。