Penetration of Nile red-loaded nanostructured lipid carriers (NLCs) across the porcine cornea.

Nile Red-loaded nanostructured lipid carriers (NR-NLCs), prepared by high-pressure homogenization technique, have been investigated for their transcorneal penetration using a confocal scanning microfluorometer (CSMF). Topical exposure of NR-NLCs led to their penetration into the epithelium and anterior stroma. The NR-NLC-40 (NR-NLCs of 40 nm) showed faster penetration compared to NR-NLC-150 (NR-NLCs of 150 nm). The surface modification of NR-NLC-40 with polyethylene glycol 400 (NR-NLC-PEG) and stearylamine (NR-NLC-SA), although did not cause any significant effect on size, resulted in an increased penetration into the epithelium concomitant with a reduced penetration into the stroma compared to the NR-NLC-40. Ex vivo mucoadhesion assay revealed that NR-NLC-PEG and NR-NLC-SA adhered more strongly to the porcine corneal surface compared to NR-NLC-40. Flow cytometry experiments with porcine corneal epithelial cells showed that NR-NLC-40 was internalized better than NR-NLC-PEG and NR-NLC-SA. These results, taken together, suggest that NLCs are potentially useful for lipophilic drug delivery to the corneal epithelium and anterior stroma without any surface modifications. However, surface modifications with polyethylene glycol 400 or stearylamine could be useful to treat ocular surface disorders.