Sustained dual release of placental growth factor-2 and bone morphogenic protein-2 from heparin-based nanocomplexes for direct osteogenesis

Objective: To compare the direct osteogenic effect between placental growth factor-2 (PlGF-2) and bone morphogenic protein-2 (BMP-2). Methods: Three groups of PlGF-2/BMP-2-loaded heparin-N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) nanocomplexes were prepared: those with 0.5 mu g PlGF-2; with 1.0 mu g BMP-2; and with 0.5 mu g PlGF-2 combined with 1.0 mu g BMP-2. The loading efficiencies and release profiles of these growth factors (GFs) in this nanocomplex system were quantified using enzyme-linked immunosorbent assay, their biological activities were evaluated using cell counting kit-8, cell morphology, and cell number counting assays, and their osteogenic activities were quantified using alkaline phosphatase and Alizarin Red S staining assays. Results: The loading efficiencies were more than 99% for the nanocomplexes loaded with just PlGF-2 and for those loaded with both PlGF-2 and BMP-2. For the nanocomplex loaded with just BMP-2, the loading efficiency was more than 97%. About 83%-84% of PlGF-2 and 89%-91% of BMP-2 were stably retained on the nanocomplexes for at least 21 days. In in vitro biological assays, PlGF-2 exhibited osteogenic effects comparable to those of BMP-2 despite its dose in the experiments being lower than that of BMP-2. Moreover, the results implied that heparin-based nanocomplexes encapsulating two GFs have enhanced potential in the enhancement of osteoblast function. Conclusion: PlGF-2-loaded heparin-HTCC nanocomplexes may constitute a promising system for bone regeneration. Moreover, the dual delivery of PlGF-2 and BMP-2 appears to have greater potential in bone tissue regeneration than the delivery of either GFs alone.