Biophysical Investigation of Nanoparticle Interactions with Lung Surfactant Model Systems

The purpose of the study was to investigate the interactions between nanoparticles and artificial lung surfactants using biophysical in vitro methods. Dipalmitoylphosphatidylcholine, the main lipid component of lung surfactant, was used as a model system. The lipid, in combination with extractions of gelatin based nanoparticles, as well as interactions of the nanoparticles in the subphase with the lipid film spread on top, were analyzed by recording surface pressure-area isotherms using a Langmuir trough. The results indicated extractions of nanoparticles alone form monolayers with reduced maximum surface pressures of approximately 10 mN/m in magnitude when compared to the lipid films (maximum surface pressures of approximately 50-55 mN/m). Increasing area per molecule values in binary mixtures showed considerable nanoparticle incorporation into the films. Present was a visibly enhanced insertion upon decreasing lipid:nanoparticle ratios and accordingly additional area occupation by the nanoparticles was observed. The high surface pressure values obtained from the isotherms of the binary mixtures indicate the notion that their size dependent incorporation does not destabilize the monolayer film. The study results demonstrated that pulmonary nanoparticle delivery is a possible route of administration. This might help assess possible toxicity related to destabilization of the surfactant film, as well as, help set upper deposition limits for inhalable formulations containing nanoparticles.