Impact of Nanostructured Lipid Carriers as an Artificial Tear Film in a Rabbit Evaporative Dry Eye Model.

PURPOSE: To characterize formulations of nanostructured lipid carriers (NLCs) as an artificial tear film and evaluate their efficacy in protecting the ocular surface epithelial cells from desiccating stress in vivo. METHODS: The physicochemical properties of NLCs, produced with components similar to the tear film such as phosphatidylcholine and squalene, were determined. In vitro cytotoxicity of NLCs was evaluated by a short-time exposure test in porcine corneal epithelial cells using a methyl thiazol diphenyl-tetrazolium bromide assay. The residence time of NLCs in rabbit eyes and the efficacy of NLCs eye drops in protecting the rabbit corneal epithelium from desiccating stress were assessed. RESULTS: Nanosized NLCs with a mean size of ∼39 ± 5 nm and a zeta potential of -30 mV could be produced and formulated into eye drop with a pH of 6.90 ± 0.01, osmolarity of 273 ± 1 mOsm/L, and surface tension of 39 ± 1 mN/m (for air interface). Eye drop formulations of NLCs were nontoxic to porcine corneal epithelial cells. NLCs drops showed higher ocular surface retention and formed a stable corneal film compared with a saline solution. Moreover, NLCs eye drops showed greater efficacy in protecting the corneal surface against desiccating stress compared with a polymer-based commercial artificial tear. CONCLUSIONS: NLCs eye drops are biocompatible in rabbit eyes and show potential as a tear replacement vehicle for the treatment of dry eye disease.

A superfusion apparatus for ex vivo human eye irritation investigations.

A superfusion apparatus (SA) was developed to maintain isolated human corneas ex vivo under conditions which mimic the natural eye environment in vivo, including controlled temperature, tear flow and intraocular pressure. The SA was designed, developed and tested for use in ophthalmic pre-clinical research and to test new pharmaceutical formulations. Corneas undergo an equilibration process in the new physiological environment for one day. The test was then initiated by the application of the test substance, incubation, and temporal assessment of corneal damage using various parameters. The effects of mild and severe irritant concentrations of NaOH (2% and 8%, respectively) on corneal opacity, swelling and epithelial integrity were studied, and the inflammatory status assessed using F4/80 and MPO as macrophages and neutrophils markers, respectively. The SA was then used to test new artificial tear formulations supplemented with silver ions as an active constituent, showing different degrees of inflammatory responses as indicated by the migration of MPO and F4/80 positive cells towards the epithelium. The human cornea superfusion apparatus was proposed as a model for acute eye irritation research.