Interactions between silica particles and model phospholipid monolayers

Abstract

The rapid increase in the air pollution level observed in recent years is considered to be one of the main social and economic problems due to the strong direct influence on living organisms. From the point of view of proper prophylaxis, explanation of the mechanism of the impact of suspended dust particles (PMs ≤ 10 µm) on model biological membranes at the molecular level is becoming increasingly important. In this work, we present the effects of the quantity and distribution of solid silica particles on the properties of Langmuir monolayers formed by the main phospholipids of biological membranes, i.e. 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-ethanolamine (POPE). Dispersions of silica particles (0.1%, 1.0% and 2.5%) have been added to the DPPC or POPE to form a mixed monolayer and investigated using a combination of Langmuir trough technique and Brewster Angle Microscopy (BAM). This study shows that the presence of silica particles (PMs) affects the run of the surface pressure–area (π–A) isotherm, leading to a different phase behaviour of the monolayer and it also has an impact on the lipid membrane morphology. Moreover, relaxation experiments of the phospholipid-PMs monolayer were performed to determine the influence of both concentration and distribution of silica particles on the stability of phospholipid membrane.