Joint Interactions of Graphene and Benzo[a]pyrene With Pulmonary Surfactant

<title>Abstract</title> <bold>Background:</bold> Airborne nanoparticles can be <sup/> inhaled and deposit in human alveoli, where pulmonary surfactant (PS) molecules line at the alveolar air-water interface to act as the first barrier against inhaled nanoparticles entering the body. Although considerable efforts have been made to elucidate the mechanisms underlying nanoparticle-PS interactions, our understanding on this important issue is limited due to the high complexity of the atmosphere, in which nanoparticles are believed to experience transformations that remarkably change the nanoparticles’ surface properties and states. By contrast with bare nanoparticles that have been extensively studied, relatively little is known about the interactions between PS and inhaled nanoparticles which already adsorb contaminants. In this combined experimental and computational effort, we investigate the joint interactions between PS and graphene with coexisting benzo[a]pyrene (BaP). <bold>Results:</bold> Depending on the BaP concentration and molecular agglomeration, different nanocomposite structures are formed via BaPs adsorption on graphene. Upon deposition of graphene carrying BaPs at the pulmonary surfactant (PS) layer, competition of interactions between different components determines the interfacial processes including BaP solubilization, graphene translocation and PS perturbation. Importantly, BaP adsorbed on graphene is solubilized to increase its bioavailability and inhibit the PS biophysical function. Translocation of graphene across the PS layer is facilitated by BaP adsorption through segregating it from contact with PS, while translocation of graphene oxide is suppressed due to increase of the surface hydrophobicity. Graphene extracts PS molecules from the layer, and the resultant PS depletion declines with graphene oxidation and BaP adsorption. <bold>Conclusion:</bold> Graphene showed high capacity of adsorbing BaPs to form nanocomposites, which were inhaled and deposit in alveoli, where competition of interactions between different components determined the interfacial processes of BaP solubilization, graphene translocation and PS perturbation.