Abstract

Lung surfactant is the lipid-protein monolayer at the interface between the air and the liquid lining the alveoli. It serves to ensure the lungs stay inflated during inhalation and to reduce the surface tension to prevent its collapse at the end of expiration. Exposure to e-cigarette additives vitamin E (a−tocopherol) and its acetate derivative vitamin E acetate (a−tocopherol acetate) through vaping has been linked to e-cigarette or vaping product use-associated lung injury (EVALI). This condition disrupts normal lung function, leading to severe respiratory distress that can cause hospitalization for difficulty in breathing, and, in some cases, lung collapse or death. Using a Langmuir balance, excess area calculations, Brewster angle microscopy (BAM), atomic force microscopy (AFM) and molecular studies such as grazing incidence X−ray diffraction (GIXD) and X−ray reflectivity (XR), the effects of these additives on the lung surfactant monolayer film have been examined and changes in surface activity, morphology, and molecular organization of the film assessed. The introduction of a−tocopherol and a−tocopherol acetate alters the fluidity, phase balance and modifies the composition of the different phases present. These changes could potentially impair normal lung surfactant function. This research also addresses potential short-term impacts on lung surfactant function due to vaping. In addition to its effects on lung surfactant, we studied a−tocopherol, the most bioavailable form of vitamin E, for its interaction with common membrane lipids. Known as a potent membrane-soluble antioxidant, a−tocopherol plays an irreplicable role in preventing lipid peroxidation, which can otherwise lead to the degradation of cellular membranes, or even cell death. We used the same techniques to explore the mixing behaviour of a−tocopherol with both saturated and unsaturated membrane lipids. This revealed how a−tocopherol’s interactions vary based on the degree of lipid unsaturation, independent of the lipids headgroup.