The pH dependent interaction between nicotine and simulated pulmonary surfactant monolayers with associated molecular modelling

Pulmonary surfactant is an endogenous material that lines and stabilises the alveolar air–liquid interface. Respiratory mechanicscan be compromised by exposure to environmental toxins such as cigarette smoke, which contains nicotine. This study aims todetermine the influence of nicotine on the activity of simulated lung surfactant at pH 7 and pH 9. In all cases, the addition ofnicotine to the test zone caused deviation in surfactant film performance. Importantly, the maximum surface pressure wasreduced for each system. Computational modelling was applied to assess key interactions between each species, with theGAUSSIAN09 software platform used to calculate electrostatic potential surfaces. Modelling data confirmed either nicotine penetration intothe two-dimensional structure or interfacial/electrostatic interactions across the underside. The results obtained from this studysuggest that nicotine can impair the ability of pulmonary surfactant to reduce the surface tension term, which can increase thework of breathing. When extrapolated to gross lung function, alveolar collapse and respiratory disease (e.g. chronic airwayobstruction) may result. The delivery of nicotine to the (deep) lung can cause a deterioration in lung function and lead to reducedquality of lif