Composite solid lipid nanoparticles with hydrogel core for delivering small hydrophilic molecules to the retina: an in vitro study using ARPE-19 and 661W cells

Abstract

In this study, we developed a novel solid lipid nanoparticle (SLN) formulation for drug delivery of small hydrophilic cargo to the retina. The new formulation, based on a gel core and composite shell, allowed up to two times increase in the encapsulation efficiency. The type of hydrophobic polyester used in the composite shell mixture affects the particle surface charge, colloidal stability, and cell internalization profile. We validated the SLN capability as a drug delivery system by performing encapsulation of a hydrophilic neuroprotective cyclic guanosine monophosphate analogue, previously demonstrated to hold retinoprotective properties, and the best formulation resulted in particles with size of {+/-} 250nm, anionic charge > -20 mV, and an encapsulation efficiency value of {+/-}60%, criteria that are suitable for retinal delivery. In vitro studies using ARPE-19 and 661W retinal cell lines revealed a relatively low SLN toxicity, even when high particle concentration was used. More importantly, SLN could be uptaken by the cells and the release of the hydrophilic cargo in the cytoplasm was visually demonstrated. These findings suggest that the newly developed SLN with a gel core and composite polymer/lipid shell holds all characteristics suitable for drug delivery of small hydrophilic active molecules into retinal cell.