Photoresponsive smart surfaces are promising candidates for a variety of applications in optoelectronics and sensing devices. The use of light as an order signal provides advantages of remote and noninvasive control with high temporal and spatial resolutions. Modification of the photoswitches with target biomacromolecules, such as peptides, DNA, and small molecules including folic acid derivatives and sugars, has recently become a popular strategy to empower the smart surfaces with an improved detection efficiency and specificity. Herein, we report the construction of photoswitchable self-assembled monolayers (SAMs) based on sugar (galactose/mannose)-decorated azobenzene derivatives and determine their photoswitchable, selective protein/cell adhesion performances via electrochemistry. Under alternate UV/vis irradiation, interconvertible high/low recognition and binding affinity toward selective lectins (proteins that recognize sugars) and cells that highly express sugar receptors are achieved. Furthermore, the cis-SAMs with a low binding affinity toward selective proteins and cells also exhibit minimal response toward unselective protein and cell samples, which offers the possibility in avoiding unwanted contamination and consumption of probes prior to functioning for practical applications. Besides, the electrochemical technique used facilitates the development of portable devices based on the smart surfaces for on-demand disease diagnosis.Keywords: azobenzene; cell adhesion; monosaccharide protein recognition; photoswitching; self-assembled monolayer;

By a facile strategy, we obtained three pure regioisomers of multiaryl coronene bisimide (CBI) derivatives via IBr-mediated annelation and subsequent Suzuki coupling reactions with high yields. A series of aromatic groups with different electron properties were efficiently introduced to obtain functional CBI derivatives under mild conditions with good yields. Furthermore, the annelation mechanism as well as the optical and electrochemical properties of CBI derivatives were further investigated.

A novel low molecular weight organogelator (LMOG) containing an azobenzene group has been designed and synthesized. Stable gels could be formed in various organic solvents. UV–Vis spectroscopy indicated that the sol-gel transition of the organogels could be reversibly tuned by UV/visible light irradiations. Importantly, scanning electron microscopy (SEM) revealed that the characteristic gelation morphologies would vary from solvents of different polarities. FT-IR, XRD and rheological measurements demonstrated that the different nanostructures in polar and non-polar solvents might result from the differences in the intermolecular hydrogen bonding, π-π stacking driving forces as well as the different stacking models for the formation of the gels. Moreover, as an efficient phase-selective gelator, this photo-switchable gel could perform as an efficient absorbent and water cleaner to remove pollutants (e.g. rhodamine B).Download high-res image (157KB)Download full-size image

We report the synthesis of a water-compatible bis-glycosyl diarylethene using click chemistry that undergoes photochromism and functions as a molecular logic gate.

In most cases, inverse type diarylethenes (DAEs) exhibit a bathochromic shift of the π-conjugation absorption band after photocyclization, which leads to “visible” closed forms and “visible” photochromic behaviors. The reason for the bathochromic shift is that the lone pair electrons on the sulfur atoms of the thiophene rings function as π-electrons and participate in π-conjugation. To make photochromic behaviors “invisible”, electron-withdrawing aldehyde groups were introduced into the inverse DAE to endow lone pair electrons on the sulfur atoms with more n-electron characteristics and then achieved the hypsochromic shift of the π-conjugation absorption band after photocyclization. As a result, the absorption changes of aldehyde modified inverse DAE (IDAEo-2CHO) remained “invisible” during isomerization, and the only fluorescence changes can be observed by the naked eye after photocyclization. Taking advantage of this unique optical feature of IDAEo-2CHO, anti-counterfeiting applications were implemented.

•Galactosyl naphthalimide-piperazine based pH fluorescence probes.•Intracellular pH sensing and subcellular organelle-targeted imaging.•Specific recognition by asialoglycoprotein receptor.•Targeted imaging of lysosome organelles in live Hep-G2 cells.•Minimal cytotoxicity for the targeted intracellular fluorogenic imaging.A series of galactosyl naphthalimide-piperazine derivatives have been synthesized as intracellular pH and lysosome-targeting imaging probes for live human hepatoma cells. The probes show good sensitivity in both aqueous buffer and intracellular environments. Incorporation of the galactose moiety with the pH probes facilitates their specific endocytosis and, thus targeted trafficking to lysosome, by the asialoglycoprotein receptor of human hepatoma cells. The acidic intracellular pH of live human hepatoma cells gives rise to a fluorescence “turn-on” signal of the probes probably via a modulation of the photo-induced electron transfer (PET) mechanism. Additionally, galactosylation of the probes enhances their selective accumulation in lysosome and decreases the cytotoxicity.A series of galactosyl naphthalimide-piperazine pH probes were designed and synthesized. The designed probes were applied in intracellular pH sensing and targeted fluorogenic imaging of lysosome with minimum cytotoxicity.

Infinite coordination polymers are recognized as excellent platform for functionalization. Dithienylethene motifs, which are one of the most attractive functional moieties, were incorporated into an infinite coordination polymer, to deliver a “smart” porous material that can response to external stimuli. The obtained dithienylethene-based infinite coordination polymers (named Cu-DTEDBA) share the advantages of both infinite coordination polymers (porosity and stability) and dithienylethene motifs (photochromism). The physical and chemical properties of Cu-DTEDBA were characterized by FTIR, TEM, SEM, XRD, TGA, UV–vis, EDX and BET. Moreover, the combination of dithienylethene and infinite coordination polymers gives rise to a synergistic effect, which induces functional behaviors of ammonia sensor applications. Both open and closed forms of Cu-DTEDBA exhibit distinct colorimetric change upon exposure to gaseous ammonia, which is not observed in dithienylethene free molecules.The incorporation of dithienylethene motifs into the skeleton of infinite coordination polymers gives rise to a synergistic effect, inducing functional behaviors of ammonia sensing applications in addition to simple photochromism.

The photo-regulated interactions between an RNA aptamer and photochromic spiropyran were investigated at a single-molecule level via an α-hemolysin nanopore. Upon irradiation of alternating UV/visible light, the translocation process of the RNA aptamer could be optically tuned on account of its different binding affinity with two photoisomers, spiropyran and merocyanine. This provides a general analytic model for understanding the mechanism of a photo-regulated biomolecule conformational change at a single-molecule level.

By a facile strategy, we obtained three pure regioisomers of multiaryl coronene bisimide (CBI) derivatives via IBr-mediated annelation and subsequent Suzuki coupling reactions with high yields. A series of aromatic groups with different electron properties were efficiently introduced to obtain functional CBI derivatives under mild conditions with good yields. Furthermore, the annelation mechanism as well as the optical and electrochemical properties of CBI derivatives were further investigated.

The photo-regulated interactions between an RNA aptamer and photochromic spiropyran were investigated at a single-molecule level via an α-hemolysin nanopore. Upon irradiation of alternating UV/visible light, the translocation process of the RNA aptamer could be optically tuned on account of its different binding affinity with two photoisomers, spiropyran and merocyanine. This provides a general analytic model for understanding the mechanism of a photo-regulated biomolecule conformational change at a single-molecule level.

In most cases, inverse type diarylethenes (DAEs) exhibit a bathochromic shift of the π-conjugation absorption band after photocyclization, which leads to “visible” closed forms and “visible” photochromic behaviors. The reason for the bathochromic shift is that the lone pair electrons on the sulfur atoms of the thiophene rings function as π-electrons and participate in π-conjugation. To make photochromic behaviors “invisible”, electron-withdrawing aldehyde groups were introduced into the inverse DAE to endow lone pair electrons on the sulfur atoms with more n-electron characteristics and then achieved the hypsochromic shift of the π-conjugation absorption band after photocyclization. As a result, the absorption changes of aldehyde modified inverse DAE (IDAEo-2CHO) remained “invisible” during isomerization, and the only fluorescence changes can be observed by the naked eye after photocyclization. Taking advantage of this unique optical feature of IDAEo-2CHO, anti-counterfeiting applications were implemented.