In vitro characterization of vascular endothelial growth factor and dexamethasone releasing hydrogels for implantable probe coatings

Anti-fouling hydrogel coatings, copolymers of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol, were investigated for the purpose of improving biosensor biocompatibility. These coatings were modified to incorporate poly(lactide-co-glycolide) (PLGA) microspheres in order to release dexamethasone (DX) and/or vascular endothelial growth factor (VEGF). DX and VEGF release kinetics from microspheres, hydrogels, and microspheres embedded in hydrogels were determined in 2-week and 1-month studies. Overall, monolithic, non-degradable hydrogel drug release had an initial burst followed by release at a significantly lower amount. Microsphere drug release kinetics exhibited an initial burst followed by sustained release for 1 month. Embedding microspheres in hydrogels resulted in attenuated drug delivery. VEGF release from embedded microspheres, 1.1±0.3 ng, was negligible compared to release from hydrogels, 197±33 ng. After the initial burst from DX-loaded hydrogels, DX release from embedded microspheres was similar to that of hydrogels. The total DX release from hydrogels, 155±35 μg, was greater than that of embedded microspheres, 60±6 μg. From this study, hydrogel sensor coatings should be prepared incorporating VEGF in the hydrogel and DX either in the hydrogel or in DX microspheres embedded in the hydrogel.