Controlled release of vascular endothelial growth factor using poly-lactic-co-glycolic acid microspheres: in vitro characterization and application in polycaprolactone fumarate nerve conduits.

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulator. Controlled release of such stimulators may enhance and guide the vascularization process, and when applied in a nerve conduit may play a role in nerve regeneration. We report the fabrication and in vitro characterization of poly-lactic-co-glycolic acid (PLGA) microspheres encapsulating VEGF and the in vivo application of nerve conduits supplemented with VEGF-containing microspheres. PLGA microspheres containing VEGF were prepared by the double emulsion-solvent evaporation technique. This yielded 83.16% of microspheres with a diameter <53 μm. VEGF content measured by ELISA indicated 93.79±10.64% encapsulation efficiency. Release kinetics were characterized by an initial burst release of 67.6±8.25% within the first 24h, followed by consistent release of approximately 0.34% per day for 4 weeks. Bioactivity of the released VEGF was tested by human umbilical vein endothelial cell (HUVEC) proliferation assay. VEGF released at all time points enhanced HUVEC proliferation, confirming that VEGF retained its bioactivity throughout the 4 week time period. When the microsphere delivery system was placed in a biosynthetic nerve scaffold robust nerve regeneration was observed. This study established a novel system for controlled release of growth factors and enables in vivo studies of nerve conduits conditioned with this system.