Effect of Nanoparticles on the Bulk Shear Viscosity of a Lung Surfactant\n Fluid

Abstract

Inhaled nanoparticles (< 100 nm) reaching the deep lung region first interact\nwith the pulmonary surfactant, a thin lipid film lining the alveolar\nepithelium. To date, most biophysical studies have focused on particle induced\nmodifications of the film interfacial properties. In comparison, there is less\nwork on the surfactant bulk properties, and on their changes upon particle\nexposure. Here we study the viscoelastic properties of a biomimetic pulmonary\nsurfactant in the presence of various engineered nanoparticles. The\nmicrorheology technique used is based on the remote actuation of micron-sized\nwires via the application of a rotating magnetic field and on time-lapse\noptical micros-copy. It is found that particles strongly interacting with lipid\nvesicles, such as cationic silica (SiO2, 42 nm) and alumina (Al2O3, 40 nm)\ninduce profound modifications of the surfactant flow proper-ties, even at low\nconcentrations. In particular, we find that silica causes fluidification, while\nalumi-na induces a liquid-to-soft solid transition. Both phenomena are\ndescribed quantitatively and ac-counted for in the context of colloidal physics\nmodels. It is finally suggested that the structure and viscosity changes could\nimpair the fluid reorganization and recirculation occurring during breath-ing.\n