Evaluating the Impact of Hydrophobic Silicon Dioxide in the Interfacial Properties of Lung Surfactant Films

Michele Ferrari,Francesca Ravera,Eduardo Guzmán,Eva Santini,Libero Liggieri

doi:10.1021/acs.est.1c06885

Abstract

The interaction of hydrophobic silicon dioxide particles (fumed silicon dioxide), as model air pollutants, and Langmuir monolayers of a porcine lung surfactant extract has been studied in order to try to shed light on the physicochemical bases underlying the potential adverse effects associated with pollutant inhalation. The surface pressure–area isotherms of lung surfactant (LS) films including increasing amounts of particles revealed that particle incorporation into LS monolayers modifies the organization of the molecules at the water/vapor interface, which alters the mechanical resistance of the interfacial films, hindering the ability of LS layers for reducing the surface tension, and reestablishing the interface upon compression. This influences the normal physiological function of LS as is inferred from the analysis of the response of the Langmuir films upon the incorporation of particles against harmonic changes of the interfacial area (successive compression–expansion cycles). These experiments evidenced that particles alter the relaxation mechanisms of LS films, which may be correlated to a modification of the transport of material within the interface and between the interface and the adjacent fluid during the respiratory cycle.

Highlights

Long-term exposure to air pollutants is accounted among the most important sources of cardiovascular diseases and mortality.[1,2] In particular, World Health Organization statistics ascribe more than one-third of the deaths caused by strokes, lung cancer, or cardiac diseases to air pollution.[3]
The purpose of this study is to explore the interaction between hydrophobic silicon dioxide particles and a commercial formulation of porcine lung surfactant (LS) (Curosurf, Chiesi Farmaceutici S.p.A., Parma, Italy) using in vitro experimental assays based on the evaluation of the modification of the equilibrium and dynamic properties of LS films as a result of the incorporation of particles
It was demonstrated that the incorporation of hydrophobic silicon dioxide particles into a minimal LS model formed only by DPPC leads to a strong modification of the interfacial behavior due to the strong interaction of the particles with the hydrophobic moieties of the lipid molecules.[42]

Summary

■ INTRODUCTION

Long-term exposure to air pollutants is accounted among the most important sources of cardiovascular diseases and mortality.[1,2] In particular, World Health Organization statistics ascribe more than one-third of the deaths caused by strokes, lung cancer, or cardiac diseases to air pollution.[3]. The role of the inhalation of silicon dioxide nanopowders in the emergence of silicosis makes it necessary to evaluate its effect on the performance of LS layers.[43] Despite the simplicity of the experimental model used in this study, it may be expected that the obtained results can contribute to the understanding of the most fundamental physicochemical bases underlying the modification of the LS performance upon the incorporation of particles This is of paramount importance because the impact of particles on the dynamic properties of fluid layers is a well-known problem from the seminal work of Lucassen[44] that is more than 30 years old and has been studied by different authors beause of their multiple fundamental and applied implications.[45−47]. ■ packing, Ac, on the silicon dioxide particle mass fraction, xp, incorporated into the Curosurf monolayer

AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES