Photolipid Bilayer Permeability is Controlled by Transient Pore Formation

Abstract

Controlling the release or uptake of (bio-) molecules and drugs from liposomes is critically important for a range of applications in bioengineering, synthetic biology, and drug delivery. In this paper, we report how the reversible photoswitching of synthetic lipid bilayer membranes made from azobenzenecontaining phosphatidylcholine (azo-PC) molecules (photolipids) leads to increased membrane permeability. We show that cell-sized, giant unilamellar vesicles (GUVs) prepared from photolipids display leakage of fluorescent dyes after irradiation with UV-A and visible light. Langmuir−Blodgett and patch-clamp measurements show that the permeability is the result of transient pore formation. By comparing the trans-tocis and cis-to-trans isomerization process, we find that this pore formation is the result of area fluctuations and a change of the area cross-section between both photolipid isomers.

Pyrrole Hemithioindigo Antimitotics with Near‐Quantitative Bidirectional Photoswitching that Photocontrol Cellular Microtubule Dynamics with Single‐Cell Precision**

“…Although E ‐ PHTub‐8 had significant residual bioactivity, its high FDR—achieved by matching the PHT scaffold's peak isomerisation efficiency to the GFP laser—was crucial for its success in achieving photoaccelerations. We also believe that enhanced dark‐active compounds based on PHTub‐8 can be useful tools for localised induction of MT polymerisation in biology, which remains a high‐value goal of reagent development [40, 56] …”

“…Photopharmacological approaches to high‐spatiotemporal‐precision manipulation of endogenous proteins have progressed significantly, enabling biological application to membranes, ion channels, and the cytoskeleton [1, 9, 40] . Photopharmaceuticals for the cytoskeleton have transitioned rapidly beyond their cellular proofs of concept showing non‐invasive, reversible, cellularly resolved optical control over MT dynamics and network structure [41] .…”

Pyrrole Hemithioindigo Antimitotics with Near-Quantitative Bidirectional Photoswitching Photocontrol Cellular Microtubule Dynamics with Single-Cell Precision

“…Photopharmacological approaches to high-spatiotemporal-precision manipulation studies of endogenous proteins have progressed significantly, enabling biological application to membranes, ion channels, and the cytoskeleton. 1,6,30 Photopharmaceuticals for the cytoskeleton have transitioned particularly rapidly beyond cellular proofs of concept for non-invasive, reversible, cellularly-resolved optical control over MT dynamics and network structure in cell culture. Despite the relatively poor functional dynamic range of the azobenzene-based PSTs (3-fold at 405/514 nm), they have been applied to powerful studies in embryos of fruit fly Drosophila melanogaster 31 , worm Caenorhabditis elegans 3 , zebrafish Danio rerio 32 , and mouse Mus musculus 33 , where they have helped to resolve questions in development and in neuroscience 34,35 .…”

Pyrrole Hemithioindigo Antimitotics with Near‐Quantitative Bidirectional Photoswitching that Photocontrol Cellular Microtubule Dynamics with Single‐Cell Precision**

“…Photopharmacological approaches to high-spatiotemporal-precision manipulation of endogenous proteins have progressed significantly,e nabling biological application to membranes,i on channels,a nd the cytoskeleton. [1,9,40] Photopharmaceuticals for the cytoskeleton have transitioned rapidly beyond their cellular proofs of concept showing noninvasive,r eversible,c ellularly resolved optical control over MT dynamics and network structure. [41] Forexample,despite the relatively poor functional dynamic range of the azobenzene PSTs( 3-fold at 405/514 nm), they have found highprecision uses in embryonic fruit fly D. melanogaster, [42] worm C. elegans, [3] zebrafish D. rerio, [43] and mouse M. musculus, [44] where they have helped to resolve questions in development and in neuroscience.…”

“…Although E-PHTub-8 had significant residual bioactivity,i ts high FDR-achieved by matching the PHT scaffoldsp eak isomerisation efficiency to the GFP laserwas crucial for its success in achieving photoaccelerations.W e also believe that enhanced dark-active compounds based on PHTub-8 can be useful tools for localised induction of MT polymerisation in biology,which remains ahigh-value goal of reagent development. [40,56] It was interesting that PHTub-8 appeared somewhat reversible while PHTub-7 did not (Figure 5e,g). We discount three suggestions for reversibility that are usually significant for photopharmacology (diffusion into/out of cells;s pontaneous E-to-Z relaxation;a nd E-to-Z photoreversion of PHTub8 by 561 nm imaging) due to the results of control experiments (see Supporting Note 3).…”