Solid lipid nanoparticles prepared by coacervation method as vehicles for ocular cyclosporine

Cyclosporine-loaded solid lipid nanoparticles were prepared according to the coacervation method: various stabilizers were used in order to obtain nanoparticles with different surface charge. These formulations were tested on rabbit corneas. Corneal irritation was measured according to opacity and permeability test; the interaction of labeled solid lipid nanoparticles with the cornea was studied by fluorescence microscopy; drug accumulation and permeation through the cornea were studied after labeling cyclosporine with a fluorescent probe. Nanoparticles were not irritant to the cornea, according to the opacity and permeability test. Cationic (chitosan coated) solid lipid nanoparticles enhanced drug accumulation and permeation through rabbit cornea, compared to anionic and non-ionic solid lipid nanoparticles and other reference formulations, probably due to the interaction of chitosan coated nanoparticles with corneal epithelial cells.