Chitosan nanoparticles as a potential drug delivery system for the ocular surface: toxicity, uptake mechanism and in vivo tolerance.

PURPOSE To study the in vitro and in vivo interaction of chitosan nanoparticles (CSNPs), a new particulate drug carrier, with epithelial cells on the ocular surface. METHODS CSNPs labeled with fluorescein isothiocyanate-bovine serum albumin were produced by ionotropic gelation. Human conjunctival epithelial cells (IOBA-NHC) were exposed for 15, 30, 60, and 120 minutes to three different CSNP concentrations. Immediately after treatment and after a 24-hour recovery period in culture medium, cell survival, and viability were measured. The association of CSNPs with IOBA-NHC cells was investigated by confocal microscopy. The influence of temperature and the effect of metabolic inhibition were studied by fluorometry. The in vivo uptake and acute tolerance of the ocular surface to CSNPs were evaluated in rabbits. RESULTS Cell survival and viability of CSNP-exposed cells were equivalent to that of the control. Uptake of CSNPs was continuous for the 2-hour duration of these experiments and was temperature dependent. Metabolic inhibition by sodium azide had no effect on CSNP uptake. The rabbit ocular surface showed no signs of inflammation or alteration after CSNP exposure compared with the control. Fluorescence microscopy of rabbit eyeball and lid sections confirmed in vivo uptake by conjunctival and corneal epithelia. CONCLUSIONS CSNPs were internalized by IOBA-NHC cells by an active transport mechanism that did not compromise cell viability. Moreover, these nanoparticles were well tolerated by the ocular surface tissues. These facts add further support for the potential use of these colloidal systems to delivery drugs to the ocular surface.