Examining the Effects of Common Vape Additives on the Interfacial Properties of Model Lung Surfactant Monolayers

The number of adolescents who report vaping has drastically increased in recent years which is alarming due to the rise in E-cigarette or Vaping Use-Associated Lung Injury (EVALI) which has symptoms including difficulty breathing, shortness of breath, and chest pain. Studies on the bronchoalveolar lavages of EVALI patients have found vape additives within the sample of fluid extracted from the lungs which were not found in healthy patients. One possible mechanism for EVALI is that the vape additives are interacting with the lung surfactants thus causing a change in the mechanical properties of the surfactant. The lung surfactant forms a monolayer film at the air-liquid interface of the alveoli which, consists primarily of surfactants such as Dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), and proteins such as SP-B and SP-C, reduces the work of breathing by reducing the surface tension in the alveoli. Conversely, damage to the film caused by foreign matter can lead to increased surface tension and difficulty in breathing. Thus, our work hypothesizes, using a model lung surfactant composed of DPPC and POPG, that common additives to vape liquids, such as cannabidiol (CBD) and vitamin E, damage the film via the displacement of lung surfactants, resulting in increased surface tension in the alveoli of the lungs. While the surface activity of lung surfactant mixture containing vitamin E have been previously studied, the effects of CBD and CBD mixed with vitamin E is an area in need of more research. In this work, we utilize a Langmuir-Pockels Ribbon Trough to emulate the mechanical dilatation of the lungs during breathing. Briefly, our experiments consist of spreading a monolayer of surfactant to an air-liquid interface and applying compression and expansion cycles while monitoring the film’s surface pressure, which is used to evaluate the effects of common vape additives on the film behavior. Additionally, dilatational rheology studies can be used to provide understanding into EVALI progression and therapeutic intervention, by examining changes in the viscoelastic properties of the film upon the addition of vape additives. The results with the model lung surfactant and CBD showed an earlier sharp increase in surface pressure upon the compression. This corresponds to a shift in the film state transition from expanded to condensed liquid, which suggests tighter interfacial packing. In addition, the maximum surface pressure upon compression decreased with increased number of cycles indicating a damaged ability of the film to return to its unstressed state. Preliminary results of the dilatational rheology did not show a significant impact of CBD addition over the measured interfacial viscoelastic moduli despite the changes in surface pressure. However, studies indicate that a concern with CBD in vaping liquids is the decomposition of CBD into cannabidiolquinone (QCBD) which could impact both the surface pressure and viscoelastic properties of the lung surfactant. Further studies should include the effects of heat and light degradation on surface activity of model lung surfactants added by vape additives such as vitamin E and CBD.