Light-responsive nanochannels based on the supramolecular host–guest system

Abstract

The light-responsive nanochannel of rhodopsin gained wider research interest from its crucial roles in light-induced biological functions, such as visual signal transduction and energy conversion, though its poor stability and susceptibility to inactivation in vitro have limited its exploration. However, the fabrication of artificial nanochannels with the properties of physical stability, controllable structure, and easy functional modification becomes a biomimetic system to study the stimulus-responsive gating properties. Typically, light-responsive molecules of azobenzene (Azo), retinal, and spiropyran were introduced into nanochannels as photo-switches, which can change the inner surface wettability of nanochannels under the influence of light; this ultimately results in the photoresponsive nature of biomimetic nanochannels. Furthermore, the fine-tuning of their stimulus-responsive properties can be achieved through the introduction of host–guest systems generally combined with a non-covalent bond, and the assembling process is reversible. These host–guest systems have been introduced into the nanochannels to form different functions. Based on the host–guest system of light-responsive reversible interaction, it can not only change the internal surface properties of the nanochannel and control the recognition and transmission behaviors but also realize the controlled release of a specific host or guest molecules in the nanochannel. At present, macrocyclic host molecules have been introduced into nanochannels including pillararenes, cyclodextrin (CD), and metal–organic frameworks (MOFs). They are introduced into the nanochannel through chemical modification or host–guest assemble methods. Based on the changes in the light-responsive structure of azobenzene, spiropyran, retinal, and others with macrocycle host molecules, the surface charge and hydrophilic and hydrophobic properties of the nanochannel were changed to regulate the ionic and molecular transport. In this study, the development of photoresponsive host and guest-assembled nanochannel systems from design to application is reviewed, and the research prospects and problems of this photo-responsive nanochannel membrane are presented.

Influence of Surface Chemistry on Host/Guest Interactions: A Model Study on Redox-Sensitive β-Cyclodextrin/Ferrocene Complexes

“…The obtained findings should be applicable to different host/ guest interactions, including photo-or redox-sensitive complexes between β-CD and other guests (e.g., azobenzene), 49,51,52,54 Fc and other hosts (e.g., cucurbit [7]uril), 6,28 and other host/guest pairs (e.g., cucurbit [8]uril/viologen and pillar[n]arene complexes), 3,6,7 and thus promote the development of well-defined functional interfaces for numerous applications in sensing, 13,28 catalysis, 3,11 material sciences, 2,3,6,7,14,44 and biomedicine. 15,34,52,54 Besides, the obtained knowledge about the interplay between surface chemistry, monolayer organization and supramolecular interactions can be applied to other ligand/receptor pairs and thus contributes to the general understanding of self-assembly and multivalent interactions at functional interfaces, 8,9,46,47 facilitating their progressive use in material and biochemical sciences.…”

“…3−7 Combined with multivalent interactions, 2,8−10 stimuli-responsive host/guest complexation allows to design surfaces with advanced properties such as strong binding, on-demand switching, self-sorting, and regeneration. Determining the factors that govern these dynamic host/guest interfaces is therefore important for various applications in material sciences (e.g., controlled assembly of molecules/nanoobjects, [1][2][3]5,6,10 patterning, 1−3,5,6 catalysis, 3,11 and mechanical actuators 4 ), sensing (e.g., small chemicals, biomolecules, and cells), 5,6,12,13 and biotechnology (e.g., controlled adhesion of cells/bacteria/viruses 3,5,6,10 and biomimetic (nano)interfaces 5,9,10,14 ).…”

“…Controlling molecular assembly on surfaces through host/guest chemistry is a rapidly growing research field with a wide range of approaches developed for the design of nanostructured, stimuli-responsive, and biomimetic interfaces. – A particularly attractive feature of host/guest interactions is the possibility to modulate their binding strength reversibly and on-demand, which can be achieved through a variety of stimuli, including electrochemistry, light, temperature, pH, soluble competitors, and their combinations. – Combined with multivalent interactions, ,– stimuli-responsive host/guest complexation allows to design surfaces with advanced properties such as strong binding, on-demand switching, self-sorting, and regeneration. Determining the factors that govern these dynamic host/guest interfaces is therefore important for various applications in material sciences (e.g., controlled assembly of molecules/nano-objects, – ,,, patterning, – ,, catalysis, , and mechanical actuators), sensing (e.g., small chemicals, biomolecules, and cells), ,,, and biotechnology (e.g., controlled adhesion of cells/bacteria/viruses ,,, and biomimetic (nano)­interfaces ,,, ).…”

Recent Progress in Photoresponsive Biomaterials

“…Stimuli-responsive molecules, which an external stimulus can manipulate, have recently received considerable interest. The use of light as a stimulus is fascinating for its precise spatiotemporal control and non-destructive nature, as the intensity and wavelength can be easily regulated [1][2][3]. Light-responsive molecules, also known as photoresponsive molecules, are a class of compounds that undergo reversible or irreversible structural changes upon exposure to light.…”

Nanofluidic Photoionic Membranes for Light Energy Harvesting and Conversion

“…The formed thermal gradient drives ion transport along the materials and enables e – transfer along the external circuit. − The solar evaporator systems have shown a solar-thermal conversion efficiency of up to ∼100%, and ∼1% of the solar energy could be ultimately converted into electricity . Nanofluidic membranes emerged initially to mimic remarkable rectification, − gating, − and selective ion transport properties, − and later were used for renewable energy harvesting applications, − mainly including osmotic energy harvesting. − Increasingly, nanofluidic membranes with light-responsive properties have been developed, − which demonstrated various light-tunable ion/molecule transport properties. − Encouragingly, many of them are able to harvest light energy, drive ions passing through the membranes (Figure C), and generate transmembrane photocurrent (i.e., short-circuit current, I sc ) and photovoltage (i.e., open-circuit voltage, V oc ), − as shown in Figure D. Compared with the electrode-based and cell-free devices, the membrane-based photoionic systems behave in a way closer to the biological light-energy harvesting systems.…”