Investigating the Effect of Vitamin E on the Viscoelastic Properties of Lung Surfactant

The utilization of e-cigarettes and vapes has become a very prevalent issue in today’s society as multitude of adolescents/teenagers have fallen victim to the vaping epidemic. Various studies have been conducted on patients with e-cigarette or vaping product use-associated lung injuries or (EVALI). These studies have observed multiple instances where vaping additives were found in the bronchoalveolar lavages of patients with reported breathing difficulties. It is hypothesized that vaping additives, upon entry to the lungs can interact with lung surfactant, disrupting the stability of the monolayer film, resulting in inflammation of the alveoli and difficulty breathing. The lung’s monolayer film exists at the air-liquid interface of the alveoli and is composed of surfactants such as Dipalmitoylphosph-atidylcholine (DPPC), 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), and proteins. These proteins and surfactants work in tandem to reduce the surface tension in the alveoli which enables a person to inhale and exhale properly. Our research focuses on the hypothesis that vape additives such as vitamin E (VitE) can interact with lung surfactant and decrease its ability to reduce surface tension in the alveoli. In this work, a Langmuir-Pockels ribbon trough was utilized to mimic the compression and expansion of the lungs during breathing. Phosphate-buffered saline (PBS) was utilized as subphase in all trials to emulate physiological conditions. Our experiments consisted of spreading a layer of model lung surfactant at the air-liquid interface, followed by compressing and expanding while monitoring the surface pressure. In addition, dilatational rheology was examined via film oscillations at minimal area change to assess the viscoelastic moduli of films. Initial control trials were carried out with pure DPPC to model unaffected lung surfactant. Furthermore, vitamin E a common additive in vape products, was added to DPPC to test the viscoelastic properties of the monolayer film formed on the interface, emulating the exposure to this vape additive. Overall, the plots generated by the expansion and compression did not retain the same shape as the pure DPPC. The phase transition present in pure DPPC compression isotherms, which characterizes the liquid expanded to liquid condensed state changes, was not seen upon the addition of VitE. Rather a higher and smoother surface pressure increase was observed. However, while a pure DPPC film results in maximum surface pressure close to 73 mN/m, the film added by VitE resulted in lower maximum surface pressures of about 64 mN/m. This suggests that VitE addition impacts intermolecular interactions at the interface. More specifically, decreasing packing density at low mean molecular areas. This can also be observed from dilatational rheology results as the viscoelastic properties measured for systems with additions of VitE saw a decrease in the viscoelastic modulus. Particularly the elastic modulus as those values decreased to a value of less than half of the unaffected model modulus. This indicates that addition of VitE significantly impacts the rheology of lung surfactants, causing instability in the alveoli. Further studies will be conducted to investigate the difference between VitE and VitE acetate, as VitE acetate is another common additive found in vaping products.