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;

Extensive efforts have been devoted to the qualification of plant extracts as green corrosion inhibitors for industrial metals, but studies that demonstrate the active component(s) of these extracts remain scarce. We report here that piperine, the major pungent component of peppers, has the best corrosion inhibitive efficiency for copper in HCl among four analogous amide alkaloids isolated from a traditional Chinese medicine. This compound inhibited HCl corrosion more efficiently than cysteine, and did not exhibit markedly decreased efficiency under several harsh experimental conditions. Electrochemical and microscopic analyses suggested that piperine could form a protective layer on the metal surface via both physisorption and chemisorption, reducing the corrosion rate. The adsorption energies of all the test compounds were calculated using a hybrid density functional theory.

A supramolecular, polymer-dot-based ensemble has been developed for the ratiometric detection of lectins and targeted delivery of glycoprobes. Self-assembly between a blue-emitting polymer dot and a red-emitting glycoprobe, results in an ensemble that shows red emission upon excitation of the polymer dot because of Förster resonance energy transfer. Resulting in ratiometric detection of lectins in buffer solution as well as targeted delivery of the glycoprobe to cells that highly express a sugar receptor. Unlike conventional systems where both the agent and vector are codelivered intracellularly, our ensemble developed here shows a receptor-controlled dissociation on the cell membrane.Keywords: cell imaging; glycoprobe; polymer dot; probe; ratiometric;

The seasonal outbreak of influenza causes significant morbidity and mortality worldwide because a number of influenza virus (IV) strains have been shown to infect and circulate in humans. Development of effective means to timely monitor as well as block IVs is still a challenging task. Whereas conventional fluorescence probes rely on a fluorimetric change upon recognizing IVs, here we developed simple “Supra-dots” that are formed through the aqueous supramolecular assembly between a blue-emitting polymer dot and red-emitting sialylglycan probes for the ratiometric detection of IVs. Tuning the Förster resonance energy transfer from polymer dots to glycan probes by selective sialylglycan–virus recognition enables the fluorescence ratiometric determination of IVs, whereas the presence of unselective, control viruses quenched the fluorescence of the Supra-dots. Meanwhile, we show that the Supra-dots can effectively inhibit the invasion of a human-infecting IV toward a human cell line, thereby making possible a unique bifunctional, supramolecular probe for influenza theranostics.Keywords: influenza; polymer dot; probe; supramolecular; virus;

•Donor-Acceptor-Donor (D-A-D) DCM dye as a new probe for amyloid β (Aβ).•The fluorogenic probe rapidly senses Aβ in aqueous solution.•The probe can image Aβ of different morphologies.•The probe quickly detects the senile plaques deposited in a transgenic mouse brain.The effective imaging of amyloid β (Aβ) in vivo is important for the diagnosis of Aβ-related diseases such as the Alzheimer's disease (AD). Here we report a donor-acceptor-donor (D-A-D) type fluorogenic probe for the rapid imaging of amyloid β (Aβ) senile plaques in a transgenic mouse brain. The probe that features a dicyanomethylene-4H-pyran (DCM) core shows a concentration-dependent fluorescence enhancement with Aβ42 and Aβ40, which are the main components of Aβ fibrils formed in the brain of AD patients. The D-A-D probe can also be used to rapidly sense Aβ peptide monomer, oligomer and fibril in an aqueous solution and image the morphologically diverse Aβ species by confocal microscopy. In particular, we demonstrate that the probe can be used to rapidly stain Aβ senile plaques in the brain of transgenic mice by intravenous injection.

The ability to simultaneously monitor multiple analytes in, for example, a single microplate well, is important for both basic research and clinical applications. In particular, for disease diagnosis there is a growing awareness that determination of a single disease biomarker is insufficient to pathologically confirm a disease state. Consequently, much recent literature has been directed towards the development of multiplexed photoluminescent sensors which can simultaneously detect multiple and diverse biomarkers that exist in a homogenous solution or a single cell, accelerating the progress towards precise disease diagnosis. This tutorial review highlights a selection of recent contributions towards this emerging interdisciplinary field that incorporates chemistry, chemical biology, materials sciences and medical sciences.

This paper discusses the use of N,N′-disubstituted-dihydrodibenzo[a,c]phenazines with typical Vibration-Induced-Emission (VIE) properties for imaging amyloid β (Aβ) fibrils, which are a signature of neurological disorders such as Alzheimer's disease. A water-soluble VIEgen with a red fluorescence emission shows a pronounced, blue-shifted emission with Aβ peptide monomers and fibrils. The enhancement in blue fluorescence can be ascribed to the restriction of the molecular vibration by selectively binding to Aβ. We determine an increasing blue-to-red emission ratio of the VIEgen with both the concentration and fibrogenesis time of Aβ, thereby enabling a ratiometric detection of Aβ in its different morphological forms. Importantly, the VIEgen was proven to be suitable for the fluorescence imaging of small Aβ plaques in the hippocampus of a transgenic mouse brain (five months old), with the blue and red emissions well overlapped on the Aβ. This research offers a new rationale to design molecular VIE probes for biological applications.

The switch in glycan-receptor specificity of influenza viruses may cause their interspecies transmission. However, tools that can simultaneous unveil the different receptor specificities of a single virus strain, in a homogeneous solution, have been elusive. Here we show a simple yet effective “2D glycosheet” that is capable of simultaneously identifying the human- and avian-glycan-receptor specificity of influenza viruses. Two fluorophores with different emission colors are coupled with avian- or human-glycan receptors. Then, the glycan–fluorophore conjugates with different receptors and emission colors are co-assembled on a 2D molybdenum disulfide platform, producing a duplexed, fluorogenic 2D glycosheet. While the system shows a single emission color with viruses containing a single receptor specificity, in the presence of a virus (H7N9) containing dual (human- and avian-) receptor specificity the system produces both emission colors. Interestingly, the use of graphene oxide and carbon nanotubes as the material substrate also produces dual emission with H7N9, thus enabling a new generation of low-dimensional glycomaterials for effectively probing the switch in receptor-specificity of influenza viruses.

Two boronate fluorescent probes have been developed for the detection of peroxynitrite (TCFB1 and TCFB2). TCFB1 was shown to have a low sensitvity towards peroxynitrite and have a poor solubility in aqueous solution whereas TCFB2 demonstrated high sensitivity towards peroxynitrite and mitochondria localisation with the ability to detect exogenous and endogenous peroxynitrite in live cells (Hep-G2, RAW 264.7, HeLa and A459).

Supramolecular self-assembly between perylenediimide-based glycoclusters and a red-emitting fluorophore produces structurally uniform and stable glyco-dots amenable to targeted fluorogenic imaging of liver and triple-negative breast cancer cells.

Here we demonstrate that low-dimensional materials (LDMs) enhance the conjugation between fluorogenic boronic acids (BAs) and saccharides. Among the LDMs investigated, 1D carbon nanotubes significantly lower the limit of detection and enhance the binding of the BA with D-fructose.

Here we show that graphene oxide greatly enhances the imaging ability of a peptide probe that selectively targets microtubules of the cytoskeleton, thus enabling the dynamic tracking of mitosis in live cells.

Three cationic conjugated polyelectrolytes (CPEs) with a common poly(p-phenylene ethynylene) backbone and different galactose-containing side chains were designed and synthesized. These CPEs were characterized and their application in targeted hepatoma cell imaging was demonstrated.

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

Supramolecular self-assembly between poly(3-hexylthiophene-2,5-diyl) (P3HT), a polymeric material extensively used for optoelectronic devices, and fluorescent glycoprobes produces core–glycoshell theranostic nanodots (glyco-dots) capable of targeted imaging and photodynamic therapy of liver and triple-negative breast cancer cells.

We have developed a theranostic nanocomposite of metallic nanoparticles that uses two distinct fluorescence mechanisms: Förster Resonance Energy Transfer (FRET) and Metal-Enhanced Fluorescence (MEF) controlled by ligand–receptor interaction. Supramolecular assembly of the fluorophore-labeled glycoligands to cyclodextrin-capped gold nanoparticles produces a nanocomposite with a quenched fluorescence due to FRET from the fluorophore to the proximal particle. Subsequently, interaction with a selective protein receptor leads to an aggregation of the composite, reactivating the fluorescence by MEF from the distal metallic particles to fluorophores encapsulated in the aggregates. The aggregation also causes a red-shift in absorbance of the composite, thereby enhancing the production of reactive oxygen species (ROS) on red-light irradiation. Our nanocomposite has proven suitable for targeted cancer cell imaging as well as multimode therapy using both the photodynamic and drug delivery properties of the composite.

Supramolecular assembly between conjugated polymers and fluorescent dyes produces a unique class of fluorogenic “nanogrenades”. These nanomaterials have shown the ability to image as well as irreversibly destruct amyloid β fibril plaques by simple light irradiation.

Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

We report an interlocked supramolecular ensemble formed between a conjugated polymer (CP) and a fluorescent glycoprobe for receptor-targeting cancer cell theranostics.

This paper describes the development of a “diffusion-to-surface” ratiometric graphene electrosensor for the selective detection of live cells and pathogens that highly express mannose-binding proteins (MBPs). MBPs have been implicated in many pathological processes and are identified on specific types of bacteria. Consequently, MBPs are a promising biomarker for targeted disease diagnosis and therapy. Here, we develop a unique electrosensor that features a ratiometric voltammetric signal for the selective probing of MBPs. Self-assembly of mannosyl anthraquinone (AQ) to a graphene oxide-decorated screen-printed electrode produces the sensor with an inherent surface-controlled voltammetric signal. Subsequently, addition of a redox probe (RP) imparts the system with a diffusion-controlled current, thus enabling a ratiometric sensing rationale for which AQ serves as a reference. While the reference current is hardly compromised by adding analytes, RP exhibits a concentration-dependent current quenching on addition of mannose-selective lectins over other proteins. Importantly, this ratiometric electrosensor has proven to be applicable for the ratiometric probing of alternatively activated macrophages and a Gram-negative bacterium highly expressing MBPs, but shows minimal response to a series of control live cells and bacteria without mannose receptor expression.Keywords: anthraquinone; bacteria; cell; electrochemistry; graphene; sensor

The synthesis of a series of new N-oxyamide-linked glycoglycerolipids and their assembly with gold nanoparticles for receptor-targeting imaging and drug delivery are reported.

This paper describes the simple construction of a unique class of supramolecular ensembles formed by electrostatic self-assembly between charged conjugated polymers and fluorophore-coupled glycoligands (glycoprobes) for the selective fluorogenic detection of receptor proteins at both the molecular and cellular levels. We show that positively and negatively charged diazobenzene-containing poly(p-phenylethynylenes) (PPEs) can be used to form stable fluorogenic probes with fluorescein-based (negatively charged) and rhodamine B based (positively charged) glycoprobes by electrostatic interaction. The structures of the ensembles have been characterized by spectroscopic and microscopic techniques. The supramolecular probes formed show quenched fluorescence in an aqueous buffer solution, which can be specifically recovered, in a concentration-dependent manner, through competitive complexation with a selective protein receptor, over a range of other unselective proteins. The ensembles also show selective fluorescence enhancement with a live cell that expresses the glycoligand receptor but not a control cell without receptor expression.

•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.

We show the construction of a library of heteroatom-fused benzo[c]carbazole derivatives by a Diels–Alder reaction as effective surface-coating materials against copper corrosion in an acidic medium.

Expression of specific transmembrane receptors by cells frequently represents an important signature of diseases, but this dynamic event can hardly be monitored directly with live cells due to the limitation of current biochemical techniques. Here we develop a pyrenyl glycoanthraquinone construct that can be firmly immobilized on a graphene-spotted screen printed electrode via strong π-interactions. The inherent current signal produced by the surface-confined glycoquinone can be used to detect selective sugar–protein recognitions with simple electrochemical techniques and portable facilities. Importantly, we demonstrate that the level of pathogenic receptors expressed by different types of live cells can be tracked with the electrode system in a label-free manner, providing a useful tool for the on-demand disease diagnosis as well as basic biochemical studies.

Intercellular glycoligand-receptor interactions are implicated in a number of disease-related processes. Effective tools that target these receptors may facilitate disease theranostics. However, owing to their low binding affinity, multivalent presentation of glycoligands is needed to increase the avidity with transmembrane receptors. While previous strategies focus on the covalent coupling of glycoligands to a synthetic backbone, we show here that the use of graphene oxide (GO) greatly enhances the cellular and tissue imaging ability of a small-molecule fluorescence glycoprobe. We determine that GO with an optimum size may serve as a clustering platform to reinforce the interaction of the glycoprobe with its selective receptor on a cancer cell. This phenomenon has been consistently observed with the xenograft tissue of a tumor-bearing mouse. Using this principle we have further constructed a supramolecular glycocomposite by co-assembling the glycoprobe and an anticancer drug onto a single GO surface. In addition to imaging ability, this material displays improved toxicity for liver cancer cells that over express the glycoprotein receptor, when compared to the control cells.

Recently, there has been increasing interest in the construction of graphene oxide (GO) based fluorogenic composite materials (FCMs) for the detection of ligand–protein recognitions, which modulate numerous physiological and pathological processes in nature. In the sensing systems developed, GO has been used as a platform to assemble, and thus quench the fluorescence of dye-labelled ligands for the fluorogenic (fluorescence off–on) detection of proteins through the competitive formation of ligand–protein complexes, disassembling the GO composite. Here we show that the size, structure and loading concentration of GO may largely impact the sensing performance of GO-based FCMs. We synthesized four glycodyes that incorporate diverse natural glycoligands (as recognition groups) coupled with fluorescent dyes (as both the graphene binding and signal reporting group) with different emission wavelengths for comparison with GOs with different sizes. We determined that with the increase of size, the quenching ability of GO for the glycodyes increased, whereas the GO with a moderate size showed the best sensing performance for lectins (proteins that recognize glycoligands). The plausible mechanism of action was proposed. This research suggests that judicious quality control of GO is crucial for the construction of GO-based FCMs as biosensors.

We have developed a galactosyl azidonaphthalimide probe for the selective fluorogenic imaging of hepatocellular H2S, an important gaseous transmitter produced in the liver.

This study describes the simple preparation of core–shell glycosyl gold nanoparticles (AuNPs) using stepwise, copper-free click chemistry-promoted self-assembly. The as-formed glyco-AuNPs can be used for the selective detection of sugar–lectin interactions, which are vital to many important physiological and pathological processes. The approach uses AuNPs as bioprobes since they produce, sensitively, changes in both color visible to the naked eye and surface plasmon resonance (SPR), on aggregation. Strain-promoted click reaction of an azido galactoside with a lipid cyclooctyne affords a galactolipid that can be embedded into polyethylene glycol (PEG)-coated AuNP via self-assembly. Subsequently, using naked-eye and plasmon resonance scattering spectroscopy, we were able to observe the colorimetric and plasmonic variations of the glyco-AuNPs, respectively, in the presence of a selective lectin over other proteins.Keywords: Au-NP; click chemistry; lectin; plasmon resonance scattering spectroscopy; SPAAC; sugar

Correction for ‘Glycosylation enhances the aqueous sensitivity and lowers the cytotoxicity of a naphthalimide zinc ion fluorescence probe’ by Lei Dong et al., Chem. Commun., 2015, DOI: 10.1039/c5cc04357c.

With this research we demonstrate that glycosylation of a naphthalimide zinc ion probe, using click chemistry, leads to an improvement of the aqueous sensitivity, working pH range and targeting ability for specific cells, together with significantly reduced cytotoxicity.

•Glyco-naphthalimide probe is developed for thiolphenol (Tp).•The probe shows ratiometric response to Tp.•The detection is transient in full aqueous solution.•Tp in real river water samples can be accurately quantified.Although being widely used in organic synthesis, thiophenol (Tp) is toxic to the human body. We report here the preparation of a ratiometric fluorescence probe for the selective, transient determination of Tp in full aqueous solution. The probe was synthesized by a click reaction coupling between an alkynyl naphthalimide-dansyl dyad and an azido galactoside which increases the water solubility. Fluorescence spectroscopic analyses showed that the probe had a specific ratiometric response to Tp transiently in a full aqueous solution, over a range of other species. The probe has also proven suitable for the quantification of Tp in environmental water samples, and possesses superior properties to previous Tp fluorescence probes in terms of water solubility and sensitivity.

•Anthraquinonyl galactoside (AG) was synthesized by CuAAC.•AG could self-assemble to a graphene electrode for impedance detection of lectins.•AG@graphene electrode could probe receptor-rich cancer cells in a label-free manner.•Knockdown of the receptor led to decreased detection signal.Detection of live cells has been difficult with conventional biochemical techniques that require the lysis of cells to release a biomarker. This study describes the simple construction of a galactosyl anthraquinone dye for the label-free impedance detection of live cancer cells. A click dipolar reaction of an alkynyl anthraquinone with azido galactoside yields the anthraquinone probe which can be subsequently employed to bind to a graphene-coated screen printed electrode by self-assembly. By taking advantage of selective sugar-receptor recognitions, live cancer cells without being labeled, can be captured by the electrode, producing a sensitive impedance signal. Knockdown of the receptor leads to a sharp decrease of the impedance signal, suggesting the suitability of the electrode system for the direct live cell capture based on ligand-receptor recognitions.

This review summarizes the recent progress in quantum dot (QD) based sensors used for the photoluminescent detection of a variety of species in vitro and in vivo. New trends in using these nanomaterials for sensing applications are highlighted.

We show here that a series of triazolyl glycolipid derivatives modularly synthesized by a “click” reaction have the ability to increase the susceptibility of a drug-resistant bacterium to β-lactam antibiotics. We determine that the glycolipids can suppress the minimal inhibitory concentration of a number of ineffective β-lactams, upward of 256-fold, for methicillin-resistant Staphylococuss aureus (MRSA). The mechanism of action has been preliminarily probed and discussed.Keywords: click reaction; MRSA; superbacteria; Triazolyl glycolipid; β-lactams

•Anomeric galactolipid mixtures have synergistic cytotoxic effect for MM.•A mixture produces more apoptotic MM cells than either anomer alone.•The mixture also induces PARP cleavage and DNA damage.This study describes an interesting observation that the mixture of anomeric galactolipids has synergistic effects on the growth inhibition of human multiple myeloma (MM) cells. We determine that the equivalent mixture of a pair of α- and β-galactolipids with a 14-carbon lipid chain can cause stronger poly ADP-ribose polymerase cleavage and DNA damage, producing more late apoptotic MM cells, than either anomer alone.

•Glyco-DPPs are constructed for lectin detection in the NIR region.•Probes can be used for the selective detection of lectins with low limit of detection.•Glyco-DPP can quantify accurately a lectin in a serum sample.•This study makes possible the extension towards target-specific imaging of tissues.This study describes the construction of aggregation-induced-emission (AIE)-based glycosyl probes for the sensitive and selective detection of sugar–lectin interactions in the near-infrared (NIR) region. Mannosyl and galactosyl diketopyrrolopyrrole (DPP) derivatives were effectively synthesized by the Cu(I)-catalyzed azide-alkyne 1.3-dipolar cycloaddition reaction. We observed that these glycodyes had typical AIE behaviors in a semi-aqueous solution with a strong fluorescence (FL) emission in the NIR region. In a buffer solution, the glycosyl DPPs at the quenching state showed sharply increased FL upon addition of a selective lectin that recognizes the glycosyl moiety of the compounds with nanomolar limits of detection. In contrast, addition of unselective lectins, proteins and ions did not fluctuate the FL. Scanning electron microscopy analyses suggested that the FL generation could probably be a result of AIE of the glyco-DPPs upon complexation with lectins. These glyco-DPPs, to the best of our knowledge, represent the first fluorogenic AIE-based probes that can sense lectins in the NIR region, providing insights for the further extension towards low-background in vivo targeted imaging of tissues that express a lectin.

This study describes the exploitation of click chemistry in the one-step molecular engineering of an unqualified rhodamine probe, leading to its considerable functional enhancement in terms of water solubility, ion selectivity, and usefulness in detecting biological and environmental samples. A dipropargyl rhodamine dye previously identified as an unselective and poorly water-soluble mercury(II) probe was used to couple with an azido polyethylene glycol (PEG) by the Cu(I)-catalyzed azide–alkyne 1,3-dipolar cycloaddition click reaction in almost quantitative yield. The simple click-engineered rhodamine probe shows, remarkably, better water solubility and mercury(II) selectivity comparing to the raw counterpart, and can be used to sensitively image mercury ions internalized by live cells and to accurately quantify the ion spiked in river water specimens. This study provides insights into the simple functional improvement of unqualified molecular dye probes via the efficient “click engineering”.Keywords: cell imaging; click chemistry; PEG; probe; rhodamine; triazole

This study depicts the ‘click’ construction of a water-soluble galactosyl rhodamine that can selectively probe mercury ions internalized by hepatoma cells over other cancer cells.

Here, we describe a novel “switch-on” biosensor based on quinonyl glycosides functionalized quantum dots (QDs) for the specific targeting and imaging of transmembrane glycoprotein receptors on the surface of cancer cells. The design of the quinonyl glycosides lies in that the quinone moiety serves as a quencher of QDs and the glycoside moiety as a biospecific ligand for targeting a receptor. We observed that the quenched photoluminescence of the quinone glycosides functionalized QDs could be significantly recovered by a specific lectin that selectively binds to the glycosides clustering the QDs but was not affected by a panel of nonspecific lectins. Moreover, we determined that quinonyl galactoside functionalized QDs could optically image the asialoglycoprotein receptors of a hepatoma cell line in a target-specific manner. This system might provide new insights into the fabrication of photoluminogenic biosensors for the analysis of the universal ligand–receptor recognitions in nature.

•A per-acetyl glycosyl rhodamine probe detects Hg2+ in a ratiometric manner.•The fluorescent acetyl glycosyl moiety of the probe serves as a FRET donor.•The probe is highly specific for Hg2+ in an 80% aqueous solution.•A plausible mechanism for the detection is proposed.This paper describes the identification of a per-acetyl glycosyl rhodamine B (RB) derivative, KB2, simply prepared by a click reaction, as a novel fluorescent ratiometric probe for mercury (II). In an 80% aqueous solution, KB2 responded to Hg2+ in a ratiometric manner with a good selectivity over a range of metal cations. Upon formation of a 1:1 probe-ion complex, the blue fluorescence of the per-acetyl glycosyl moiety of KB2 is quenched, along with the emergence of a bright red fluorescence attributable to the lactam ring-opening form of RB. This is probably caused by a fluorescence resonance energy transfer from the acetyl glycoside as a donor to the acceptor RB–Hg2+ motif. This study provides unique insight into the design of ratiometric chemoprobes for heavy metals based on the simple coupling of per-acetyl glycosides with fluorogenic dyes.

•One hit is identified to be selectively toxic to multiple myeloma cells.•The hit is not toxic to a control cell line.•The hit induced apoptosis of multiple myeloma cells.A bis-triazolyl phenylalaninyl galactoside was synthesized by a two-fold click reaction between an azido phenylalanine and a di-O-propynyl galactoside. By a cytotoxicity assay the compound was determined to be selectively toxic for multiple myeloma (MM) among a series of cancer cell lines with no toxicity to a control cell line. A Western blot analysis suggested that this compound could potentiate the cleavage of poly ADP-ribose polymerase in MM cells, leading to apoptosis.

This study reveals that a dipropargyl rhodamine B derivative previously described as a reaction-based irreversible palladium probe responds, however, more sensitively to mercury with a reversible “turn-on” fluorescence. The probe also shows a much better imaging ability for mercury than for palladium in live cells.

Bis-triazolyl indoleamine-based chemosensors that respond to copper, and then fluorine as presumably facilitated by the high-affinity interaction between F− and the NH-proton of indole, are reported. Remarkable fluorimetric as well as colorimetric alternations upon the specific ligand–ion recognitions were observed.

The corrosion inhibitive efficiency of diverse 1,2,3-triazolyl benzyl glucoside-, galactoside- and mannoside-serine/threonine conjugates readily synthesized via CuI-catalyzed azide–alkyne cycloaddition reaction (Cue-AAC) for mild steel in HCl was examined via electrochemical impedance spectroscopy. The results indicate that these compounds are potent corrosion inhibitors even in highly concentrated HCl solutions. The potential mechanism of three inhibitors was characterized in detail via polarization and isotherm calculations. This study implies that benzyl glycoside-amino acid hybrids effectively constructed via the Cue-AAC between the highly biocompatible sugars and amino acids may represent a new class of promising and potentially green corrosion inhibitors.Graphical abstractHighlights► Triazolyl benzyl glycoside-amino acid conjugates as new corrosion inhibitors. ► They inhibit HCl corrosion for mild steel at low concentrations. ► Mechanism of inhibitors 7, 10, and 12 investigated in detail. ► They obey Langmuir isotherm and adopt dominantly chemisorption.

Despite natural amino acids having been proposed as the green surrogate of currently used corrosion inhibitors that are generally toxic to both nature and human body during the everyday industrial processing of metallic equipments, their structural simplicity yet lowers the inhibitive potency, thereby hampering their further industrialization. We disclose here that a concise chemical ligation (CuI-catalyzed azide–alkyne 1,3-dipolar cycloaddition reaction [Cue-AAC]) between two l-amino acids that are weak or noncorrosion inhibitors may result in their largely improved protective effect for mild steel in HCl. A series of 1,4-disubstituted 1,2,3-triazolyl bis-amino acid derivatives constituted by l-serine, l-threonine, l-phenylalanine, and l-tyrosine were efficiently synthesized via Cue-AAC and deprotection reactions in high yields. Subsequently performed electrochemical impedance spectroscopy (EIS) evidenced that the inhibitive effect of these compounds for mild steel in 1 M HCl is markedly better than that of their natural amino acid counterparts. The inhibitive modality of the most potent inhibitor was interpreted in detail by potentiodynamic polarization and thermodynamic calculations. Furthermore, quantum chemical calculations suggest that the triazole ring formed by the Cue-AAC has contribution to their metal surface adsorption. This study would offer unique insights into the facile development of potency-enhanced green corrosion inhibitors based on the concise Cue-AAC ligation of natural amino acids.

The anomeric mixture of a series of O-galactolipid derivatives is revealed to be more toxic against several cancer cell lines than their either single component with the pure α- or β-configuration. This interesting phenomenon has been confirmed on pairs of synthesized O-galactosyl anomers bearing length-varied alkyl chains at the lipid end. Furthermore, the most potent mixture was determined inoffensive to a normal cell line tested.

Glycoligands, which feature a glycoside as the central template incorporating Lewis bases as metal chelation sites and various fluorophores as the chemical reporter, represent a range of interesting scaffolds for development of chemosensors. Here, new types of triazolyl bidentate glycoligands (TBGs) based on the grafting of 3-azidocoumarin to the C2,3- or C4,6-positions of three epimeric pyranoglycosides including a glucoside, a galactoside, and a mannoside were efficiently synthesized via a fluorogenic dual click reaction assisted by microwave irradiation. The desired TBGs were afforded in high conversion rates (>90%) and reasonable yields (∼70%). Moreover, a preliminary optical study of two hydroxyl-free glucoside-based TBGs indicates that these compounds are strongly fluorescent in pure water, implying their potential for ion detections in aqueous media.

Triazolyl glycolipid derivatives constructed via CuI-catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction (Cue-AAC) represent a new range of carbohydrate-based scaffolds for use in many fields of the chemical research. Here the surface adsorptive ability of series of our previously prepared C1- or C6-triazole linked gluco- and galactolipid derivatives for mild steel in 1 M HCl was studied via electrochemical impedance spectroscopy (EIS). Results indicated that these monosaccharide–fatty acid conjugates are weak inhibitors against HCl corrosion for mild steel. Moreover, some newly synthesized triazolyl disaccharide (maltose)–fatty alcohol conjugates failed to display enhanced activity, meaning that the structural enlargement of the sugar moiety does not favor the iron surface adsorption. However, a bis-triazolyl glycolipid derivative, which was realized by introducing a benzenesulfonamide group via Cue-AAC to the C6-position of a C1-triazolyl glucolipid analog, eventually showed significantly improved adsorptive potency compared to that of its former counterparts. The corrosion inhibitive modality of this compound for mild steel in HCl was subsequently studied via potentiodynamic polarization and thermodynamic calculations.Graphical abstractHighlights► Triazolyl monosaccharide–fatty acid derivatives show weak adsorptive efficiency for mild steel in HCl. ► Triazolyl disaccharide–fatty alcohol conjugates fail to exhibit improved potency. ► Bis-triazolyl glycolipid derivative 31 is much more potent than all counterparts. ► The inhibitive modality of 31 was studied by polarization.

We have developed a novel class of simple materials for sensing monosaccharides by the functionalization of graphene oxide (GO) with boronate-based fluorescence probes (BA1 and BA2). The composite materials were characterized by atomic force microscopy, Raman spectroscopy, and UV–vis/fluorescence spectroscopy. The strong fluorescence of the BA probes is quenched in the presence of GO through fluorescence resonance energy transfer. The BA@GO composite sensors formed provide a useful platform for fluorogenic detection of monosaccharides based on the strong affinity between the boronic acid receptor and monosaccharides. The BA@GO composite sensor displayed a “turn-on” fluorescence response with a good linear relationship toward fructose over a range of other saccharides.

Here we demonstrate the simple construction and characterization of a pyrenyl glycoside-coated 2D MoS2 material composite capable of selectively capturing proteins and live cells on an electrode, as determined by differential pulse voltammetry.

Supramolecular assembly between conjugated polymers and fluorescent dyes produces a unique class of fluorogenic “nanogrenades”. These nanomaterials have shown the ability to image as well as irreversibly destruct amyloid β fibril plaques by simple light irradiation.

We have developed a theranostic nanocomposite of metallic nanoparticles that uses two distinct fluorescence mechanisms: Förster Resonance Energy Transfer (FRET) and Metal-Enhanced Fluorescence (MEF) controlled by ligand–receptor interaction. Supramolecular assembly of the fluorophore-labeled glycoligands to cyclodextrin-capped gold nanoparticles produces a nanocomposite with a quenched fluorescence due to FRET from the fluorophore to the proximal particle. Subsequently, interaction with a selective protein receptor leads to an aggregation of the composite, reactivating the fluorescence by MEF from the distal metallic particles to fluorophores encapsulated in the aggregates. The aggregation also causes a red-shift in absorbance of the composite, thereby enhancing the production of reactive oxygen species (ROS) on red-light irradiation. Our nanocomposite has proven suitable for targeted cancer cell imaging as well as multimode therapy using both the photodynamic and drug delivery properties of the composite.

We have developed a galactosyl azidonaphthalimide probe for the selective fluorogenic imaging of hepatocellular H2S, an important gaseous transmitter produced in the liver.

Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

This study depicts the ‘click’ construction of a water-soluble galactosyl rhodamine that can selectively probe mercury ions internalized by hepatoma cells over other cancer cells.

Intercellular glycoligand-receptor interactions are implicated in a number of disease-related processes. Effective tools that target these receptors may facilitate disease theranostics. However, owing to their low binding affinity, multivalent presentation of glycoligands is needed to increase the avidity with transmembrane receptors. While previous strategies focus on the covalent coupling of glycoligands to a synthetic backbone, we show here that the use of graphene oxide (GO) greatly enhances the cellular and tissue imaging ability of a small-molecule fluorescence glycoprobe. We determine that GO with an optimum size may serve as a clustering platform to reinforce the interaction of the glycoprobe with its selective receptor on a cancer cell. This phenomenon has been consistently observed with the xenograft tissue of a tumor-bearing mouse. Using this principle we have further constructed a supramolecular glycocomposite by co-assembling the glycoprobe and an anticancer drug onto a single GO surface. In addition to imaging ability, this material displays improved toxicity for liver cancer cells that over express the glycoprotein receptor, when compared to the control cells.

Recently, there has been increasing interest in the construction of graphene oxide (GO) based fluorogenic composite materials (FCMs) for the detection of ligand–protein recognitions, which modulate numerous physiological and pathological processes in nature. In the sensing systems developed, GO has been used as a platform to assemble, and thus quench the fluorescence of dye-labelled ligands for the fluorogenic (fluorescence off–on) detection of proteins through the competitive formation of ligand–protein complexes, disassembling the GO composite. Here we show that the size, structure and loading concentration of GO may largely impact the sensing performance of GO-based FCMs. We synthesized four glycodyes that incorporate diverse natural glycoligands (as recognition groups) coupled with fluorescent dyes (as both the graphene binding and signal reporting group) with different emission wavelengths for comparison with GOs with different sizes. We determined that with the increase of size, the quenching ability of GO for the glycodyes increased, whereas the GO with a moderate size showed the best sensing performance for lectins (proteins that recognize glycoligands). The plausible mechanism of action was proposed. This research suggests that judicious quality control of GO is crucial for the construction of GO-based FCMs as biosensors.

Here we demonstrate that low-dimensional materials (LDMs) enhance the conjugation between fluorogenic boronic acids (BAs) and saccharides. Among the LDMs investigated, 1D carbon nanotubes significantly lower the limit of detection and enhance the binding of the BA with D-fructose.

Here we show that graphene oxide greatly enhances the imaging ability of a peptide probe that selectively targets microtubules of the cytoskeleton, thus enabling the dynamic tracking of mitosis in live cells.

Expression of specific transmembrane receptors by cells frequently represents an important signature of diseases, but this dynamic event can hardly be monitored directly with live cells due to the limitation of current biochemical techniques. Here we develop a pyrenyl glycoanthraquinone construct that can be firmly immobilized on a graphene-spotted screen printed electrode via strong π-interactions. The inherent current signal produced by the surface-confined glycoquinone can be used to detect selective sugar–protein recognitions with simple electrochemical techniques and portable facilities. Importantly, we demonstrate that the level of pathogenic receptors expressed by different types of live cells can be tracked with the electrode system in a label-free manner, providing a useful tool for the on-demand disease diagnosis as well as basic biochemical studies.

We report an interlocked supramolecular ensemble formed between a conjugated polymer (CP) and a fluorescent glycoprobe for receptor-targeting cancer cell theranostics.

Small-molecular probes capable of monitoring and interfering with the activity of biomacromolecules – such as polysaccharides, nucleotides and proteins – are of paramount importance to the advancement of life science. However, such probes that can detect and simultaneously modulate the construction of biomacromolecules are elusive. Here we report a fluorogenic, foldable glycoprobe that can recognize and assemble a protein receptor in a synchronous fashion. The glycoprobe synthesized by introducing a glycoligand (for protein recognition) to a bola-type bis-fluorophore conjugate shows a “self-shielded” fluorescence in the folded state. Association with a receptor protein rapidly unfolds the probe, releasing a fluorophore capable of crosslinking the proteins – as determined using small-angle X-ray scattering – thereby producing a unique fluorescent supramolecular construct. We have demonstrated the use of the foldable glycoprobe in order to track the endocytic cycle of a transmembrane receptor.

The synthesis of a series of new N-oxyamide-linked glycoglycerolipids and their assembly with gold nanoparticles for receptor-targeting imaging and drug delivery are reported.

With this research we demonstrate that glycosylation of a naphthalimide zinc ion probe, using click chemistry, leads to an improvement of the aqueous sensitivity, working pH range and targeting ability for specific cells, together with significantly reduced cytotoxicity.

Correction for ‘Glycosylation enhances the aqueous sensitivity and lowers the cytotoxicity of a naphthalimide zinc ion fluorescence probe’ by Lei Dong et al., Chem. Commun., 2015, DOI: 10.1039/c5cc04357c.

Three cationic conjugated polyelectrolytes (CPEs) with a common poly(p-phenylene ethynylene) backbone and different galactose-containing side chains were designed and synthesized. These CPEs were characterized and their application in targeted hepatoma cell imaging was demonstrated.