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 mum 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 similar to50% at 22 mJ/m(2) and totally submersed at film surface tensions of less than or equal to15 mJ/m(2). These results suggest that the surface tension in the intrapulmonary conducting airways of hamsters may reach less than or equal to15 mJ/m(2) and that respirable particles (<10 μm in diameter) are wetted and displaced into the surface lining layer, which may facilitate interactions with many lung cells.