Ocular tolerance to a topical formulation of hyaluronic acid and chitosan-based nanoparticles.

Hyaluronic acid-chitosan nanoparticles (HA-CS NPs) have the potential to serve as a reliable drug delivery system to topically treat ocular surface disorders. We evaluated the in vivo uptake by ocular structures, the acute tolerance, and possible alterations of tear film physiology in rabbits. Fluorescent HA-CS NPs (fl-HA-CS NPs) were prepared by ionotropic gelation using fluoresceinamine-labeled hyaluronic acid and resuspended in buffer. fl-HA-CS NPs (30 microL, 0.5 mg/mL) and fluoresceinamine-HA conjugate (30 microL) were instilled into rabbit eyes every 30 minutes for 6 hours. In vivo uptake and acute tolerance were characterized 24 hours after the first instillation and compared with preinstillation measurements. Clinical signs, including tear production, lacrimal drainage system patency and reflux, and ocular surface pathology, were evaluated. The rabbits showed no signs of ocular discomfort or irritation after exposure to HA-CS NPs. No macroscopic alteration in ocular surface structures was observed. fl-HA-CS NPs were present inside conjunctival and corneal epithelial cells, although the distribution within the cells was different. The fl-HA-CS NPs had no significant effects on tissue morphology and functionality, tear production, or drainage. Taken together, these data demonstrate that HA-CS NPs are a safe drug carrier for ocular surface application.