Abstract
Abstract: :
Purpose: To assess the desiccation protection capability of various demulcents in the artificial tear formulations by an in vitro desiccation model using both human conjunctival and corneal epithelial cell lines. Methods: The assay was conducted in a cell culture plate containing 96 wells. Both human corneal epithelial cell (CEPI 17) and Chang's conjunctival cell (Clone 1-5C-4) were adopted for the study. After removing the medium and rinsing with PBS, the confluent cells were incubated with the test solutions at 37oC for 15 minutes. The cells were then subjected to desiccation inside an airflow hood for 10 to 30 minutes at room temperature after removing the test solutions. At the end of desiccation the cells were rinsed with PBS, and MTT viable dye (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) was added to the cells to react at 37oC for 4 hours. The blue crystals produced by the viable cells were then extracted with acid isopropanol after removing the MTT. The plate was read at 570 nm with a microplate reader. Wells with serum medium and wells with PBS were also run in the same plate as a total viable and a dead control, respectively. Results: The results indicated that most of the formulations containing various polymers such as HPMC, CMC, dextran, hyaluronate, HP-guar, PVA etc., as demulcents are able to provide varying amounts of protection ranging up to 80% after 10 to 30 minutes desiccation in both cell lines. Formulations with HPMC and HP-guar provided better protection compared to that with CMC, hyaluronate, and PVA. However, the formulations preserved with either BAC or the so-called "disappearing preservatives" provide poorer desiccation protection due to the cell viability affect of the preservative itself used in the formulations. Conclusions: This in vitro model/methodology is able to quantitatively assess the desiccation protection capability of various demulcents in the artificial tear formulations and provides some information about the cell viability affect of various preservatives in them.
Keywords: cornea: tears/tear film/dry eye