Lung surfactant (LS) is a complex lipid protein mixture that forms the interfacial lining in the alveoli of the lungs consequently reducing the surface tension to near zero value and thus preventing the lungs from collapse.Owing to the expanding field of nanomedicine and 2 unavoidable encounter from the atmosphere, it is crucial to study the potential effects of exposure of nanoparticles (NPs) on the lung surfactant system.In the present study, we found that two different sized hydrophobic polymeric nanoparticles diameters between ~12 and ~150 nm have contrasting effect on the functional and structural behavior of the model LS films.