Multiscale Dynamics of Lipid Vesicles in Polymeric Microenvironment

TL;DR

This study investigates how viscoelastic polymer environments influence the multiscale dynamics of lipid vesicles, revealing unprecedented coupling effects and thermal behaviors relevant for tissue engineering and cell membrane modeling.

Contribution

It provides new insights into the hierarchical dynamics of lipid membranes in polymeric microenvironments using multiple experimental techniques.

Findings

Polymer chain length affects lipid bilayer microviscosity and dynamics.

Unprecedented dynamic coupling between polymers and lipid membranes was observed.

Thermal stiffening of polymer liposome solutions depends on liposome concentration and polymer chain length.

Abstract

Understanding dynamic and complex interaction of biological membranes with extracellular matrices plays a crucial role in controlling a variety of cell behavior and functions, from cell adhesion and growth to signaling and differentiation. Tremendous interest in tissue engineering has made it possible to design polymeric scaffolds mimicking the topology and mechanical properties of the native extracellular microenvironment; however, a fundamental question remains unanswered: that is, how the viscoelastic extracellular environment modifies the hierarchical dynamics of lipid membranes. In this work, we used aqueous solutions of poly(ethylene glycol) (PEG) with different molecular weights to mimic the viscous medium of cells and nearly monodisperse unilamellar DMPC DMPG liposomes as a membrane model. Using small angle Xray scattering (SAXS), dynamic light scattering, temperature modulated differential scanning calorimetry, bulk rheology, and fluorescence lifetime spectroscopy, we investigated the structural phase map and multiscale dynamics of the liposome polymer mixtures. The results suggest an unprecedented dynamic coupling between polymer chains and phospholipid bilayers at different length and time scales. The microviscosity of the lipid bilayers is directly influenced by the relaxation of the whole chain, resulting in accelerated dynamics of lipids within the bilayers in the case of short chains compared to the polymer free liposome case. At the macroscopic level, the gel to fluid transition of the bilayers results in a remarkable thermal stiffening behavior of polymer liposome solutions that can be modified by the concentration of the liposomes and the polymer chain length.