Dilatational properties and morphology of surface films spread from clinically used lung surfactants

The dilatational properties, structure, and morphology of the surface films spread at the air–water interface from complex lipid/protein systems were studied by measuring the surface pressure–area and surface potential–area isotherms, the surface rheological properties, and AFM images. The commercially available lung surfactants Alveofact, Curosurf, Survanta, and Exosurf were used as examples.The isotherms of the studied lung surfactant surface films are compared with model lipid and protein monolayers spread from bulk solutions. On the basis of a simple rheological model, the values for the elasticity and the specific time of relaxation related to the reorganization processes occurring in the monolayers were calculated. The spread films of natural surfactants Curosurf and Alveofact show a high effectiveness of spreading and respreading under the conditions of this study. These observations were confirmed by AFM imaging.