Effects of chitosan and chitosan N-acetylcysteine solutions on conjunctival epithelial cells

Aim of the study

Chitosan, a partially deacetylated polysaccharide derived from chitin, and chitosan-N-acetylcysteine (C-NAC), a thiolated chitosan, both show enhanced retention times on the ocular surface when compared to other polymers commonly used in eye drops. To evaluate these compounds as adjuvants for ocular drug delivery or uptake of topically administered conjunctival vaccines, biochemical characteristics of both polymers were investigated in vitro and in vivo.

Methods

Human conjunctival epithelial (HCjE) cells were used to investigate biocompatibility of buffered chitosan and C-NAC containing formulations. Cellular uptake was studied using fluorescein-isothiocyanate (FITC)-labelled polymers. Transepithelial electrical resistance (TEER) measurements were performed to determine effects of chitosan on tight junctions of stratified HCjE cells in vitro. In vivo uptake of topically applied chitosan into conjunctival epithelial cells was investigated in guinea pigs.

Results

Minimal effects on cell viability were seen with both compounds after application for 30 min in a concentration of 0.1%. In vitro uptake into HCjE cells was only observed with the chitosan containing solution. An effect on tight junctions was demonstrated by significantly (P < .05) decreasing TEER levels 60 min after incubation with chitosan. In vivo, FITC-labelled chitosan was detected within guinea pig conjunctival epithelial cells 120 min after topical administration. No adverse effects were observed.

Conclusions

Results demonstrated that chitosan is taken up into conjunctival epithelial cells in vitro and in vivo, therefore fulfilling some of the requirements of an adjuvant for conjunctival mucosal vaccines. C-NAC is also well tolerated but not taken up by cells, making it a good candidate for ocular formulations supposed to persist on the ocular surface for an extended period of time.