Effects of E-Liquids and Their Aerosols with and Without Flavors on OKF6/TERT-2 Oral Epithelial Cells: Consequences of Heating and Aerosolization on Cell Viability

Background: Multiple effects of flavored E-liquids or E-liquid aerosols on various cell lines have been reported. However, concentrations of E-liquids and aerosols are not usually equivalent, making it difficult to determine the relative effect heating and aerosolization plays on the cells tested. To match concentrations of E-liquids with their aerosols, the mass and the concentration of the E-liquid nicotine dissolved in culture media must be compared to that of the aerosol bubbled into the culture media. The aim of this study is to compare the effects of equivalent amounts of E-liquids and their aerosols ± flavors (tobacco, menthol, cinnamon, strawberry and blueberry) on the morphology and viability of OKF6/TERT-2 oral epithelial cells. Methods: HPLC-UV was used to measure nicotine concentrations in culture media containing E-liquids or aerosols. Morphology and viability of OKF6/TERT-2 cells exposed to equivalent amounts of E-liquids or aerosols over a 24 h period were subsequently assessed using light microscopy, LDH cytotoxicity assays, flow cytometry and DAPI staining. Results: One hundred puffs of aerosol bubbled into 50 mL of media is equivalent to 0.17% E-liquid. As indicated by altered morphology, increased LDH activity, flow cytometry and DAPI fluorescent staining, OKF6/TERT-2 cells are negatively impacted by 100 puffs of aerosols flavored with strawberry resulting in reduced cell viability, while the same amount of E-liquids directly administered have minimal to no effect. Conclusions: The data suggests that heating and aerosolization enhance the cytotoxic effect of strawberry flavored E-liquid.