Decoding E-Cigarette Secrets: Unveiling Saliva and E-Liquid Composition through Fourier-Transform Infrared Spectroscopy

Electronic cigarettes (e-cigs), initially introduced as smoking cessation aids, have given rise to a new wave of nicotine dependence. A critical question that has emerged is the potential adverse effects of e-cig use on oral health, particularly how the vapor emitted from these devices may alter the salivary composition of users. Here, we investigate the salivary composition of e-cig users and analyze the e-liquids (flavorings) using Fourier-transform infrared (FTIR) spectroscopy. Saliva samples were categorized into two groups: e-cigarette users (25 individuals) and nonsmokers/nonusers (25 individuals). Additionally, 26 e-liquid samples used by the e-cig users were collected, with 17 obtained before use and 9 after use. The analysis provided reliable results in distinguishing between the two groups. Notably, partial least-squares discriminant analysis (PLS-DA) demonstrated a high degree of accuracy (>90%) in differentiating the sample groups. Our findings revealed a higher concentration of polysaccharides, aromatic amino acids, and inorganic phosphates, along with a lower concentration of esterases in the saliva of e-cigarette users. These alterations in salivary composition may be linked to an increased risk of type 2 diabetes, hypertension, cardiovascular diseases, kidney diseases, and tumor formation, having a negative impact on oral immunity. In contrast, no significant molecular or compositional changes were observed in the e-liquids after use. Our results underscore the importance of continued research into potential biomarkers and the long-term health effects associated with the growing prevalence of e-cigarette use as a form of nicotine consumption.