The plasma membrane surrounds every single cell and essentially shapes cell life by separating the interior from the external environment. Thus, maintenance of cell membrane integrity is essential to prevent death caused by disruption of the plasma membrane. To counteract plasma membrane injuries, eukaryotic cells have developed efficient repair tools that depend on Ca 2+ -and phospholipid-binding annexin proteins. Upon membrane damage, annexin family members are activated by a Ca 2+ influx, enabling them to quickly bind at the damaged membrane and facilitate wound healing. Our recent studies, based on interdisciplinary research synergy across molecular cell biology, experimental membrane physics, and computational simulations show that annexins have additional biophysical functions in the repair response besides enabling membrane fusion. Annexins possess different membrane-shaping properties, allowing for a tailored response that involves rapid bending, constriction, and fusion of membrane edges for resealing. Moreover, some annexins have high affinity for highly curved membranes that appear at free edges near rupture sites, a property that might accelerate their recruitment for rapid repair. Here, we discuss the mechanisms of annexin-mediated membrane shaping and curvature sensing in the light of our interdisciplinary approach to study plasma membrane repair.

Novel RNA-based technologies provide an avenue of possibilities to control the regulation of gene expression in cells. To realize the full potential of small interfering RNA (siRNA)-based therapy, efficient delivery vehicles and novel strategies for triggering release from carrier vehicles have to be developed. Gold nanoparticles (AuNPs) with sizes of ∼50–150 nm have the ability to accumulate in tumor tissue and can be transported across the membrane by endocytosis. Therefore, a laser-controlled oligonucleotide release from such particles is of particular interest. Here, we quantify the loading of specifically attached microRNA oligonucleotides (miRNA) onto single gold nanoparticles with diameters of 80, 100, 150, and 200 nm. We show that AuNPs have a curvature-dependent density of miRNA loading: the higher the curvature, the higher the loading density. Moreover, we demonstrate how one sensing strand of an RNA duplex can be dehybridized and hence released from the AuNP by heating the AuNP by irradiation with a near-infrared (NIR) laser. Laser-induced release is also demonstrated inside living cells. Together, these findings show that plasmonic nanoparticles with high curvatures are ideal carriers of oligonucleotides into cells, and their cargo can be released in a controlled manner by a thermoplasmonic mechanism. Importantly, this remotely controlled release strategy can be applied to any cargo attached to a plasmonic nanocarrier, on either the single particle or ensemble level.

Living cells respond to nanoscopic thermoplasmonic injury by recruiting an annular ring of annexin V.

,I dunnP restholm, IlirianaQ oqaj, ChristinaB.R iel, To bias V. Rostgaard, Nora Saleh, HannibalM.S chultz, Mark Standland,Jens S. Svenningsen, RasmusTruels Sørensen, JesperV isby,E milie L. Wolff-Sneedorff, Malte Hee Zachariassen, Edmond A. Ziari, Henning O. Sørensen, and Thomas Just Sørensen* [a] To Professor Klaus Bechgaard and Professor ThomasB jørnholm for always teaching to think outside the box Abstract: Ionic self-assembly (ISA) is ap rovenm ethod that exploits non-covalenti nteractions to generate supramolecular materials. Here, we have expanded the scope of this approach fabricating thin films with nanoscopic order maintained over centimeters. Cationiclayers of benzalkonium surfactants form al amellar template. The template is able to host layers of negatively charged polyaromatic functional units, hered emonstrated with b-naphthol-derived azo-dyes. We show that av arietyo ft hese functional building blocks can be incorporated in the lamellar templatet hrough ISA. Sixteen different materials were produced,c haracterized, and processedi nto thin films, with lamellar order perpendicular to the substrate. Thus, ad esign concept is demonstrated in which diverse functional motifs can be isolated and ordered in a2 Dl attice between layers of alkyl chains in bulk and in thin films, in which the molecular orderi sm aintained and alignedt othe substrate.

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