Method: Human oral keratinocyte cells were seeded into 96-wells plates overnight. Survival of the cells post-drying was measured to determine the time required to decrease the cell viability to <50%. The dryness prevention effects of three polymers were evaluated at single or multiple concentrations. Specifically, xanthan gum (0.2%), carboxymethyl chitosan (0.05, 0.1, 0.2 and 0.4%) and carbopol (0.05, 0.1, 0.2 and 0.4%). The cells were treated with the polymers for two minutes at room temperature and then removed by aspiration. The cells were then air dried at room temperature and the viability was measured. Additionally, the dryness prevention effect over time was assessed by measuring cell viability up to 4 hours. In this experiment all three polymers were tested at 0.2% and in a further experiment xanthan gum was also evaluated at 1%. A positive result was indicated by >50% viability.
Result: 15-20 minutes air drying was required to decrease the cell viability by >50%. 0.2% xanthan gum maintained cell viability at 90%. Both carboxymethyl chitosan and carbopol showed dose-response trends. However, 0.4% carboxymethyl chitosan only maintained cell viability at 40%, whereas 0.4% carbopol maintained cell viability at 60%. Xanthan gum at 0.2% and 1% maintained cell viability up to 90% for 30 and 120 minutes respectively.
Conclusion: Prior to a clinical study, this method potentially provides an effective format for the screening of moisturising agents for dry mouth relief.