Photoregulation of Mass Transport through a Photoresponsive Azobenzene-Modified Nanoporous Membrane

Abstract

Photoresponsive nanoporous membranes, composed of monosized pores modified with azobenzene ligands, were prepared on an ITO working electrode using an evaporation-induced self-assembly procedure. They exhibited the size-selective photoregulated mass transport of two ferrocene-based molecular probes through the membrane to the electrode surface as determined using a chronoamperometry technique. The measured oxidative current increased and decreased in response to alternating UV and visible light exposure correlating strongly with the photoisomerization state of the azobenzene ligands. This indicates that the optically switchable conformation (trans or cis) of azobenzene ligands controls the effective pore size and, correspondingly, transport behavior on the nanoscale.

Enzyme-Responsive Intracellular Controlled Release Using Nanometric Silica Mesoporous Supports Capped with “Saccharides”

“…[17][18][19] The first gated SMPS was developed by Fujiwara et al 20,21 via reversible photodimerization of coumarin attached to the pore outlets that were sensitive to light. Since then, other photochemical gated systems based on cis-trans isomerization of azobenzene moieties, [22][23][24][25] the association and light-operated dissociation of a α-cyclodextrin with azobenzene groups [26][27][28] and the spiropyran-merocynine photo switchable transformation 29 have been reported. pH is also a widely used stimulus for the control of mass transport in mesoporous materials.…”

Drug delivery systems based on nucleic acid nanostructures

“…Most of these mechanisms rely on external stimuli to trigger the liberation of drugs like the presence of small molecules [135] or enzymes [136], changes in the redox potential [137] or pH [138] and photoirradiation [139]. A key role in the release process play different kinds of capping agents that include organic molecules, gold nanoparticles, polymers, antibodies and DNA.…”

Azobenzene Polymers for Photonic Applications

“…In other cases, the transport properties can be photocontrolled not via binding but on the basis of changes in pore sizes (Sata et al, 2000;Abraham and Purushothaman, 1998;Kano et al, 1980). In a particularly elegant example, the size of nanochannels could be modified by irradiating azo ligands that decorate the channel walls (Liu et al, 2004). Azoderivatized gramicidin ion channels represent a unique case where ion transport can be photocontrolled by the optical manipulation of a biomolecule (Lien et al, 1996).…”