RESUMO
PURPOSE: To develop a controlled-drug delivery system for the long-term inhibition of vascular endothelial growth factor (VEGF) and its mediated responses. METHODS: Poly(lactic-co-glycolic)acid (PLGA) microspheres containing anti-VEGF RNA aptamer (EYE001) formulations in the solid-state were developed by an oil-in-oil solvent evaporation process. In vitro experiments were performed to characterize the release profiles. Stability and bioactivity of the released drug were assayed by monitoring the RNA aptamer's ability to inhibit VEGF-induced cell proliferation in human umbilical vein endothelial cells (HUVECs). Cell proliferation experiments were conducted with aptamer aliquots collected after short-, mid-, and long-term release time points. To investigate the feasibility of this polymer device as a potential transscleral delivery device, an in vitro apparatus was developed to assess polymer hydration and degradation through rabbit sclera and subsequent delivery through it. RESULTS: PLGA microspheres were able to deliver EYE001 in a sustained manner, with an average rate of 2 micro g/d over a period of 20 days. Solid-state stabilization of the aptamer with disaccharide trehalose before lyophilization and encapsulation in PLGA rendered the drug more stable after release. Cell proliferation experiments demonstrated that the bioactivity of the aptamer was preserved after release, as indicated by inhibition of endothelial cell proliferation after incubation with VEGF. Microspheres packed into a sealed chamber and placed onto the "orbital" part of a rabbit sclera for a period of 6 days became hydrated and started to degrade, as shown by scanning electron microscopy (SEM). As a result, the aptamer was delivered from the microspheres through the sclera, as determined spectrophotometrically. CONCLUSIONS: The loading of aptamer-containing microspheres into a device and placing it on the orbital surface of the sclera was assessed and shown to be feasible. RNA aptamer EYE001 encapsulated in PLGA was delivered over a period of 20 days with retained activity. This method represents a promising approach for the transscleral delivery of drugs and the treatment of choroidal and retinal diseases.
