Influence of surface chemistry and topography of particles on their immersion into the lung's surface-lining layer.

Inhaled and deposited spherical particles, 1-6 micrometer in diameter and of differing surface chemistry and topography, were studied in hamster intrapulmonary conducting airways and alveoli by electron microscopy. Polystyrene and Teflon particles, as well as puffball spores, were found submersed in the aqueous lining layer and adjacent to epithelial cells. The extent of particle immersion promoted by a surfactant film was assessed in a "floating-drop-surface balance" by light microscopy. Teflon and polystyrene spheres were immersed into the subphase by 50-60% at film surface tensions of 25 and 30 mJ/m(2), respectively, and totally submersed at 15 and 25 mJ/m(2), respectively. Puffball spores were immersed by approximately 50% at 22 mJ/m(2) and totally submersed at film surface tensions of </=15 mJ/m(2). These results suggest that the surface tension in the intrapulmonary conducting airways of hamsters may reach </=15 mJ/m(2) and that respirable particles (<10 micrometer in diameter) are wetted and displaced into the surface lining layer, which may facilitate interactions with many lung cells.