Photocontrol of ion permeation in lipid vesicles with (bola)amphiphilic spirooxazines

Abstract

Three (bola)amphiphilic spirooxazines have been synthesized and their photochromism has been characterized. The large biphotochromic structure of 2 significantly affects its conformational flexibility and the rate constants for thermal ring closure are particularly dependent on the lipid phase state. Two comprehensive ion permeation studies were performed to examine the effect of spirooxazine inclusion and isomerization on membrane permeability. In all cases, the open-ring isomers of these spirooxazines are more disruptive in bilayer membranes than their closed-ring isomers. Further, the rate of ion permeation and net release are highly dependent on the lipid bilayer phase state and the relative position of the photochromic moiety in the bilayer membrane. Moreover, the difference in potassium ion permeability under UV and visible irradiation is more pronounced than previously reported photoresponsive membrane disruptors with reversible photocontrols.

Light‐Driven Proton Transfer for Cyclic and Temporal Switching of Enzymatic Nanoreactors

“…[ 5,35 ] In the development of “complex adaptive systems,” [ 36 ] that is, life‐like, bioinspired, intelligent, adaptive, and interactive materials, the isomerization of photochromic systems such as azobenzenes and spiropyrans is actively used for the establishment of cell mimics (e.g., liposomes with artificial or semi‐synthetic channel/pore proteins) with spatiotemporal and reversible control over membrane permeability. [ 1,3,4,7,10,22,29,37–40 ] These studies are inspired by cells as out‐of‐equilibrium systems that use temporal, parallel, and synchronized biological actions to move, communicate, and replicate. Moreover, previous efforts have paved the way to create self‐adaptive [ 41 ] and light‐responsive, wavelength‐selective [ 31,32 ] polymersomes with switchable membrane permeability for the release of cargo and control of enzymatic reactions “on demand”.…”

“…[ 11,42–45 ] Recently, light‐induced proton‐pumps (LIPPs) have been unidirectionally incorporated within polymeric and liposomal vesicles to pump protons into the lumen [ 46,47 ] or outside of the vesicles [ 48 ] and to fabricate larger complex cellular compartments with LIPPs inducing artificial photosynthetic processes. [ 49,50 ] Inspired by these results, light‐driven proton transfer triggered by the switching of MEH/SP [ 51,52 ] (Scheme 1) and its derivatives [ 51,53,54 ] has been successfully applied for the temporal control of pH switches, [ 51,52 ] proton‐catalyzed reactions, [ 51 ] proton/ion transfer through bilipid vesicles, [ 38 ] self‐assembly of nanoparticles, [ 55 ] and proton‐driven molecular machines. [ 27,28,56 ] Moreover, this process is also involved in the cyclic spatiotemporal control over the dynamic assembly of SiO 2 –Pt Janus particles [ 57 ] and the disappearing of images with time.…”