Synergistic effects of dual growth factor delivery from composite hydrogels incorporating 2-N,6-O-sulphated chitosan on bone regeneration.

A promising strategy to accelerate bone generation is to deliver a combination of certain growth factors to the integration site via a controlled spatial and temporal delivery mode. Here, a composite hydrogel incorporating poly(lactide-co-glycolide) (PLGA) microspheres was accordingly prepared to load and deliver the osteogenic rhBMP-2 and angiogenic rhVEGF165 in the required manner. In addition, 2-N,6-O-sulphated chitosan (26SCS), which is a synergetic factor of growth factors, was incorporated in the composite hydrogel as well. The system showed a similar release behaviour of the two growth factors regardless of 26SCS inclusion. RhBMP-2 loaded in PLGA microspheres showed a sustained release over a period of 2 weeks, whereas rhVEGF165 loaded in hydrogel eluted almost completely from the hydrogel over the first 16 days. Both growth factors retained their efficacy, as quantified with relevant in vitro assays. Moreover, an enhanced cell response was achieved upon the delivery of dual growth factors, compared to that obtained with a single factor. Furthermore, in the presence of 26SCS, the system revealed significantly upregulated alkaline phosphatase activity, human umbilical vein endothelial cell proliferation, sprouting, nitric oxide secretion, and angiogenic gene expression. This study highlighted that the composite hydrogel incorporated with 26SCS appears to constitute a promising approach to deliver multiple growth factors. From our findings, we could also conclude that rhBMP-2 can promote angiogenesis and that the mechanism is worthy of further study in subsequent research.