Softening of phospholipid membranes by the adhesion of silica nanoparticles – as seen by neutron spin-echo (NSE)

Abstract

The interactions between nanoparticles and vesicles are of significant interest both from a fundamental as well as from a practical point of view, as vesicles can serve as a model system for cell membranes. Accordingly the effect of nanoparticles that bind to the vesicle bilayer is very important with respect to understanding their biological impact and also may shed some light on the mechanisms behind the effect of nanotoxicity. In this study we have investigated the influence of small adsorbed silica nanoparticles (SiNPs) on the structure of zwitterionic DOPC vesicles. By a combination of SANS, cryo-TEM, and DLS, we observed that the SiNPs are bound to the outer vesicle surface without significantly affecting the vesicle structure. Most interestingly, by means of neutron spin-echo (NSE) local bilayer fluctuations were studied and one finds a small but marked decrease of the membrane rigidity upon binding of the nanoparticles. This surprising finding may be a relevant aspect for the further understanding of the effects that nanoparticles have on phospholipid bilayers.

Enhanced dynamics in the anomalous melting regime of DMPG lipid membranes

“…1(b)–1(d) and 1(f)–1(g) are fits to in which the first term accounts for the diffusion of the vesicles with diffusion constant, D , that were measured with dynamic light scattering (DLS, see the Methods Section and supplementary material for more details). 43–45 The second term is the stretched exponential function predicted by Zilman and Granek for membrane bending fluctuations with a relaxation rate Γ b . 46,47 Γ b was the only fit parameter.…”

Human Liver Microsomes Immobilized on Magnetizable Beads: A Novel Approach to Study In Vitro Drug Metabolism

“…4) considering that HLM do not adsorb particularly well to the surface of laboratory glass containers. However, interactions between silica beads and phospholipids have been well documented (Hata et al, 2014;Hoffmann et al, 2014;Kettiger et al, 2016) and implicated in the membrane-disrupting properties of drug-delivering silica nanoparticles, which manifest clinically as hemolytic toxicity (Pavan et al, 2013;Hata et al, 2014;Hoffmann et al, 2014;Kettiger et al, 2016). Unlike proteins, phospholipids are negatively charged at neutral pH, and as such, electrostatic interactions are less likely to contribute to their binding.…”

High-resolution neutron spectroscopy using backscattering and neutron spin-echo spectrometers in soft and hard condensed matter

“…Thus, these theoretical and experimental efforts have led to a unifying picture that enables the extraction of the main elastic and viscous parameters of the membrane through NSE measurements 77 . This type of neutron study has been used to investigate the effect of different components in the membrane, such as various lipids [78][79][80][81] , cholesterol 82 , drugs 83 , proteins [84][85][86] and nanoparticles 87,88 .…”