In vitro cytotoxicity evaluation of electronic cigarette liquids and their main chemical components

In order to investigate the cytotoxicity of e-cigarette liquids (e-liquids) and the effects of their main chemical components on the cytotoxicity, a method for evaluating the cytotoxicity of e-liquids was established by comparing responses and detection sensitivities using a range of cytotoxicity assays. These included lactate dehydrogenase assay (LDH), bromodeoxyuridine incorporation assay (BrdU), WST-1 assay, and CCK-8 assay for cytotoxicity of e-liquids to Chinese hamster ovary cells (CHO cells) and human lung cancer cells (A549 cells). A total of 16 e-liquids were analyzed to assess the responses from the market collection. Linear regression and Pearson correlation analyses were used to study the correlation between the cytotoxicity of the e-liquids and the contents of nicotine, 1, 2-propylene glycol and glycerol in the e-liquids. The results showed that:1) The IC₅₀ values of the cytotoxicity of the e-liquids were in the sequence of CCK-8 < WST-1 < BrdU < LDH. 2) The lowest toxic effect concentration and half inhibition concentration of CHO cells induced by the e-liquids were lower than those of A549 cells. 3) Although the difference of the cytotoxicity among the 16 e-liquids was up to 5.47 times, the regression coefficients and Pearson correlation coefficients were significantly lower than those required by the linear correlation (P < 0.05) between the cytotoxicity of the e-liquids and the contents of nicotine, 1, 2-propylene glycol and glycerol. Therefore, CHO cells and CCK-8 assay are more suitable for evaluating the cytotoxicity of e-liquids. Meanwhile, there was no significant linear correlation between the cytotoxicity of the e-liquids and its main components (nicotine, 1, 2-propylene glycol and glycerol) in the experimental range.