Dynamic Manipulation of Cell Membrane Curvature by Light-Driven Reshaping of Azopolymer

Abstract

Local curvatures on the cell membrane serve as signaling hubs that promote curvature-dependent protein interactions and modulate a variety of cellular processes including endocytosis, exocytosis, and the actin cytoskeleton. However, precisely controlling the location and the degree of membrane curvature in live cells has not been possible until recently, where studies show that nanofabricated vertical structures on a substrate can imprint their shapes on the cell membrane to induce well-defined curvatures in adherent cells. Nevertheless, the intrinsic static nature of these engineered nanostructures prevents dynamic modulation of membrane curvatures. In this work, we engineer light-responsive polymer structures whose shape can be dynamically modulated by light and thus change the induced-membrane curvatures on-demand. Specifically, we fabricate threedimensional azobenzene-based polymer structures that change from a vertical pillar to an elongated vertical bar shape upon green light illumination. We observe that U2OS cells cultured on azopolymer nanostructures rapidly respond to the topographical change of the substrate underneath. The dynamically induced high membrane curvatures at bar ends promote local accumulation of actin fibers and actin nucleator Arp2/3 complex. The ability to dynamically manipulate the membrane curvature and analyze protein response in real-time provides a new way to study curvature-dependent processes in live cells.

Geometric pinning and antimixing in scaffolded lipid vesicles

“…In turn, the resulting modulation of local curvature serves to recruit curvature-sensing proteins and lipids, which may further stabilize or increase local curvature differences 2 – 5 . Recent experiments on cells subject to controlled deformation, have confirmed the primary role of spatial curvature for inducing actin polymerization and recruiting curvature sensitive proteins 6 , 7 .…”

Modulation of Immune Responses by Particle Size and Shape

“…As discussed in this review, many proteins and lipids involved in signaling and cytoskeleton-anchoring are sensitive to membrane curvature ( 129 , 130 , 156 , 157 , 187 – 189 ). Therefore, regions on particles with high positive or negative curvature might well result in phagosomal domains of protein/lipid interactions and signaling.…”

“…Nano-topography-based methods such as electron-beam (E-beam) lithography can be used to create nanostructures as small as 50–100 nm, which enables high membrane curvatures ( 188 – 190 ). These approaches can be used for studying a wide range of questions related to curvature-induced distribution of clathrin-dependent endocytic proteins ( 187 ), polymerization of F-actin ( 188 , 189 ) and nuclear membrane deformations affecting chromatin distribution and gene expression ( 190 ). Using this approach, it was found that nano-topographies of above 30 nm are sensed by macrophages and printed patterns above 71 nm in height induce higher endocytic activity ( 193 ).…”

Azopolymer‐Based Nanoimprint Lithography: Recent Developments in Methodology and Applications

“…Because DPL offers facile control of the morphology, it can be incorporated into many other fields. A recent study applied photoinduced reshaping of azopolymers in bioscience (Figure d) . Soft lithography was used to fabricate azopolymer pillar arrays, and it was found that the membrane curvatures of the cells were dynamically changed, in confined environments, by azobenzene nanostructures.…”