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

TL;DR

This study investigates how specific nanoparticles alter the bulk viscoelastic properties of lung surfactant, revealing significant fluidification or solidification effects that could impact lung function.

Contribution

It provides novel insights into nanoparticle-induced changes in lung surfactant bulk properties using microrheology, a less explored area compared to interfacial effects.

Findings

Silica causes surfactant fluidification.

Alumina induces a transition to a soft solid.

Nanoparticles significantly modify surfactant flow properties.

Abstract

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