Effects of Electronic Cigarette E-Liquids on the Adhesion and Growth of Osteoblast Cells

Electronic cigarettes (E-cigarettes) were designed to replace traditional cigarettes to decrease the harmful effects of smoking. The liquid in e-cigarettes contains different chemicals, such as Propylene Glycol (PG) and Vegetable Glycerin (VG), and may contain nicotine. To be more attractive, e-liquids are supplemented with flavorings. Because vaped e-liquids are shown to be damaging to oral tissues, similar effects could occur in the oral cavity with non-vaped e-liquids. We evaluated the effects of non-vaped e-liquid constituents on osteoblast behavior. For this purpose, human osteoblast cells (MG-63) were exposed to e-liquid containing 70% PG -30% VG with and without tobacco flavor and with or without nicotine at 12, 18 mg/mL, or no nicotine content. The e-liquids were used at various concentrations (0, 1, and 5%). To evaluate the effect of the e-liquids on osteoblast morphology and adhesion, optical microscope observations and viable cell counting using trypan blue exclusion were used. Cell growth was also analyzed using the Methyl Thiazol Tetrazolium (MTT) assay, while cytotoxicity was tested by measuring Lactate Dehydrogenase (LDH) levels after cell exposure for 24 h to the e-liquids. Our results show that e-liquids induced significant morphological changes evidenced by round cell forms, with no contact between cells. Adhesion was significantly reduced, particularly in the presence of nicotine. E-liquids at a concentration of 5% significantly reduced osteoblast growth. This effect was observed with both flavored and non-flavored e-liquid with or without nicotine. The decreased osteoblast adhesion and growth after exposure to e-liquid was confirmed by increased levels of LDH. Overall results indicate the potentially harmful effects of e-liquid non-vaped chemicals on bone cells, which could lead to the impairment of bone regeneration and tissue remodeling processes.