Specific uptake of folate-decorated triamcinolone-encapsulating nanoparticles by retinal pigment epithelium cells enhances and prolongs antiangiogenic activity

We are proposing folate-decorated polymeric nanoparticles as carriers of poorly soluble drug molecules for intracellular and prolonged delivery to retinal pigment epithelium (RPE) cells. RPE is a monolayer of epithelial cells that forms the outer blood-retinal barrier in the posterior segment of the eye, and is also implicated in the pathology of, such as neovascularization in age-related macular degeneration (AMD). In this study, folate-functionalized poly(ethylene glycol)-b-polycaprolactone (folate-PEG-b-PCL) were synthesized for assembling into nanoparticles of ~ 130 nm. These nanoparticles were internalized into ARPE-19 (human RPE cell line) via receptor-mediated endocytosis, and the cellular uptake was significantly higher than particles without folate modification. Triamcinolone acetonide (TA) was efficiently encapsulated (> 97%) into the folate-decorated nanoparticles and was slowly released over a period of 4 weeks at pH 5.5 and 8 weeks at pH 7.4. The enhanced uptake and controlled release resulted in prolonged anti-angiogenic gene expression of RPE cells. In cell culture, the down-regulation of vascular endothelial growth factor (VEGF) and up-regulation of pigment epithelium derived factor (PEDF) lasted for at least 3 weeks. Unlike benzyl alcohol, the surfactant found in commercial formulation, folate-modified nanoparticles were non-toxic. Furthermore, TA became less cytotoxic by being encapsulated in the nanoparticles. Our findings suggest that folate-PEG–PCL nanoparticles are promising drug carriers for RPE targeting.