The Effect of Nanosized Silicon Molybdate Anions on the Plasma Membrane of Human Fetal Fibroblasts

Abstract

We used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study changes in the composition of the plasma membranes of human fetal fibroblasts under the action of nanosized anions of silicon molybdic acid. The dependences of the mass spectra of the main lipids of the plasma membranes on the silicon molybdate concentration were measured and interpreted; the dependences correlate with the layer-by-layer distributions and with the affinity of cholesterol for phospholipids. A new effect for cell biochemistry was discovered, that is, a significant decrease in the relative concentrations of cholesterol and sphingomyelin in plasma membranes under the effect of multiply charged heteropoly anions (HPAs). In aqueous silicon molybdate solutions with a concentration of c ≈ 10 µM/L and an exposure time of 48 h, the amount of cholesterol in plasma membranes decreased by 2–2.5 times, while the amount of sphingomyelin decreased by 20–25%. A new mechanism is proposed for the initial effect of HPA on plasma membranes, which consists of selective etching by multiply charged anions. According to the proposed mechanism, cholesterol and sphingomyelin, the main regulators of permeability and microviscosity of plasma membranes, are extracted from the plasma membrane at the first stage of the interaction of the polyoxometallate anion with the cell. As a consequence of the increased permeability of the plasma membranes in cells, acceleration of vital transmembrane and lateral processes may occur.