In vitro effects of ethanol and mouthrinse on permeability in an oral buccal mucosal tissue construct

The current study investigated the influence of ethanol and ethanol-containing mouthrinses on model chemical permeability in an in vitro oral buccal mucosal construct (EpiOral, ORL-200, MatTek). Innate ethanol transport and metabolism in the tissue construct was also studied. Caffeine flux in buccal tissue was measured after pre-treatment with < 26.9% ethanol or Listerine® products under conditions modeling a typical mouthwash rinsing. Specifically, a 30 s exposure to alcohol products followed by a 10 h non-treatment phase and then a second 30 s exposure prior to addition of caffeine. At 10 min specific intervals, media was collected from the basal part of the tissue insert for HPLC analysis of caffeine. The results demonstrated no increase in caffeine flux due to prior exposure to either ethanol or Listerine®, and the flux and permeability constants were derived from the linear phase. No cytotoxicity or histopathological effects were observed in these tissues. We also studied the transepithelial transport and metabolism of ethanol in these tissues. Transport of ethanol was concentration-dependent with rate of diffusion proportional to the concentration gradient across the membrane. The potential metabolism of ethanol in the EpiOral construct was addressed by analyzing the remaining level of ethanol after incubation and de novo accumulation of acetaldehyde or acetic acid in culture media. Incubation for 30 min incubation resulted in no change in ethanol level up to 2000 mM, the highest concentration tested. No acetaldehyde or acetic acid was detected in culture media. In conclusion, ethanol and ethanol-containing mouthrinse treatment modeled after a typical daily mouthrinse pattern had no apparent effect on the permeability of the standard model chemical, caffeine. This exposure also had no effect on the viability of the tissue construct or histopathology, and uptake of ethanol was rapid into the tissue construct.