Probing lipid membrane bending mechanics using gold nanorod tracking

TL;DR

This study uses gold nanorod tracking via high-speed microscopy to measure the mechanical properties of lipid membranes and living cell membranes, revealing insights into their viscosity, rigidity, tension, and coupling to cellular structures.

Contribution

It introduces a novel method of probing membrane mechanics by tracking single gold nanorods, providing detailed measurements of physical parameters in both model and living cell membranes.

Findings

Membrane viscosity, bending rigidity, and tension can be determined from nanorod motion.

Membrane undulations hinder nanorod rotation in a tension-dependent manner.

Nanorod motion reveals membrane physics and coupling to the actomyosin cortex in living cells.

Abstract

Lipid bilayer membranes undergo rapid bending undulations with wavelengths from tens of nanometers to tens of microns due to thermal fluctuations. Here, we probe such undulations and the membranes' mechanics by measuring the time-varying orientation of single gold nanorods (GNRs) adhered to the membrane, using high-speed dark field microscopy. In a lipid vesicle, such measurements allow the determination of the membrane's viscosity, bending rigidity and tension as well as the friction coefficient for sliding of the monolayers over one another. The in-plane rotation of the GNR is hindered by undulations in a membrane tension dependent manner, consistent with simulations. The motion of single GNRs adhered to the plasma membrane of living cultured cells similarly reveals that membrane's complex physics and coupling to the cell's actomyosin cortex.