An Ir(III) complex chemosensor for the detection of thiols

A visual ratiometric fluorescence sensor for glutathione response based on MnO2 nanowires as an oxidant, quencher and recognition unit

As the "mother of antioxidants", glutathione (GSH) plays an important role in physiological functions. Rapid and accurate monitoring of GSH is of great significance for medicinal chemistry, food chemistry, and clinical medicine. We herein report a visual ratiometric fluorescence sensor based on MnO₂ nanowires (MnO₂ NWs) as an oxidant, quencher and recognition unit for the determination of GSH. The powerful ratiometric fluorescent probe was constructed by mixing thiamine (VB₁) and rhodamine B (RhB) with the help of MnO₂ NWs. MnO₂ NWs could not only effectively quench the fluorescence of RhB due to the inner filter effect (IFE), but also oxidized non-fluorescent VB₁ to blue fluorescent thiochrome (oxVB₁). Upon interaction with GSH, the quenched RhB fluorescence could be rapidly restored through decomposition of MnO₂ NWs into Mn²⁺, while the oxVB₁ fluorescence decreased, showing an apparent color change from blue to red. The concentration of GSH was proportional to the ratio of fluorescence intensities of RhB and oxVB₁, and the detection linear range was 1 to 10 000 μM with comparable selectivity. This ratio fluorescence sensor was successfully applied to GSH determination in whitening capsules and glutathione tablets with satisfactory results, and the sensor may be a potentially powerful tool for the detection of GSH.

The chronological evolution of small organic molecular fluorescent probes for thiols

Abnormal concentrations of biothiols such as cysteine, homocysteine and glutathione are associated with various major diseases. In biological systems, the structural similarity and functional distinction of these three small molecular thiols has not only required rigorous molecular design of the fluorescent probes used to detect each thiol specifically, but it has also inspired scientists to uncover the ambiguous biological relationships between these bio-thiols. In this minireview, we will discuss the evolution of small organic molecular fluorescent probes for the detection of thiols over the past 60 years, highlighting the potent methodologies used in the design of thiol probes and their particular applications in the semi-quantification of cellular thiols and real-time labelling. At the same time, the present challenges that limit their further application will be discussed. We hope that this minireview will promote future research to enable deeper insight into the crucial role of thiols in biological systems.

The chronological evolution of small organic molecular fluorescent probes for thiols: from separation dependency analysis to cellular specific analysis, what's next?

Efficient and very selective dual mode chemosensor for Cd(II) ions in live cells

A sensitive dual mode chemosensor NS-1 comprising Nitrobenzoxadiazole and salicylhydrazide conjugate has been synthesized via single step reaction. The probe NS-1 is characterized by analytical techniques such as multi nuclear NMR techniques and Mass spectrometry. The probe is showing a strong change in color from yellow to red on treatment of Cd(II) ions, interestingly its shows bright "Switch-ON" fluorescence state upon binding of Cd²⁺ ions in buffer solution whereas other cations did not showed any color change as well as fluorescent change. Interestingly the probe NS-1 did not results in the any color and fluorescence change with the adding together of Zn(II) ions, hence the probe is able to differentiate between Cd(II) ions from Zn(II). Further the color change and turn-on fluorescence can be rationalized by the interruption of internal charge transfer upon binding of Cd(II) ions with NS-1. The Internal charge transfer disturbance led to fluorescence change of the receptor NS-1 upon addition of Cd²⁺ has been further supported by TD-DFT calculations. The limit of detection was found to be 6.31 nano molar. The association constant was found to be 7.97*10⁴ M^-1 using Benesi-Hildebrand plot method. MTT assay suggesting that the probe NS-1 is least toxic to cells and it will be widely applicable to image Cd(II) ions in living cells via fluorescence imaging.

Self-assembly as a key player for materials nanoarchitectonics

The development of science and technology of advanced materials using nanoscale units can be conducted by a novel concept involving combination of nanotechnology methodology with various research disciplines, especially supramolecular chemistry. The novel concept is called 'nanoarchitectonics' where self-assembly processes are crucial in many cases involving a wide range of component materials. This review of self-assembly processes re-examines recent progress in materials nanoarchitectonics. It is composed of three main sections: (1) the first short section describes typical examples of self-assembly research to outline the matters discussed in this review; (2) the second section summarizes self-assemblies at interfaces from general viewpoints; and (3) the final section is focused on self-assembly processes at interfaces. The examples presented demonstrate the strikingly wide range of possibilities and future potential of self-assembly processes and their important contribution to materials nanoarchitectonics. The research examples described in this review cover variously structured objects including molecular machines, molecular receptors, molecular pliers, molecular rotors, nanoparticles, nanosheets, nanotubes, nanowires, nanoflakes, nanocubes, nanodisks, nanoring, block copolymers, hyperbranched polymers, supramolecular polymers, supramolecular gels, liquid crystals, Langmuir monolayers, Langmuir-Blodgett films, self-assembled monolayers, thin films, layer-by-layer structures, breath figure motif structures, two-dimensional molecular patterns, fullerene crystals, metal-organic frameworks, coordination polymers, coordination capsules, porous carbon spheres, mesoporous materials, polynuclear catalysts, DNA origamis, transmembrane channels, peptide conjugates, and vesicles, as well as functional materials for sensing, surface-enhanced Raman spectroscopy, photovoltaics, charge transport, excitation energy transfer, light-harvesting, photocatalysts, field effect transistors, logic gates, organic semiconductors, thin-film-based devices, drug delivery, cell culture, supramolecular differentiation, molecular recognition, molecular tuning, and hand-operating (hand-operated) nanotechnology.

Nitroolefin-modified cyclometalated iridium(iii) complexes for tunable detection of biothiols with deep-red emission

Two nitroolefin-modified cyclometalated iridium(iii) complexes were employed as turn-on probes for the rapid (1 min) detection of biothiols with tunable emission.

A novel label-free electrochemical immunosensor based on the enhanced catalytic currents of oxygen reduction by AuAg hollow nanocrystals for detecting carbohydrate antigen 199

Herein, bimetallic alloyed AuAg hollow nanocrystals (AuAg HNCs) were prepared by a simple one-pot aqueous method using polycytidysic acid (PCA) as the green growth-directing agent. The novel immunosensor for carbohydrate antigen 199 (CA199) was further constructed based on the enhanced catalytic currents of oxygen reduction reaction (ORR) by AuAg HNCs. By virtue of the good biocompatibility and catalytic activity of AuAg HNCs, the immunosensor exhibited superior analytical performance for the assay of CA199 under the optimal experimental conditions, the ORR signals linearly decreased with the increased CA199 concentrations in the range of 1 ~ 30UmL^-1, with the low detection limit of 0.228UmL^-1, improved stability, reproducibility and selectivity.

Luminescent Strategies for Label-Free G-Quadruplex-Based Enzyme Activity Sensing

By catalyzing highly specific and tightly controlled chemical reactions, enzymes are essential to maintaining normal cellular physiology. However, aberrant enzymatic activity can be linked to the pathogenesis of various diseases. Therefore, the unusual activity of particular enzymes can represent testable biomarkers for the diagnosis or screening of certain diseases. In recent years, G-quadruplex-based platforms have attracted wide attention for the monitoring of enzymatic activities. In this Personal Account, we discuss our group's works on the development of G-quadruplex-based sensing system for enzyme activities by using mainly iridium(III) complexes as luminescent label-free probes. These studies showcase the versatility of the G-quadruplex for developing assays for a variety of different enzymes.

A cyclometalated iridium(III) complex used as a conductor for the electrochemical sensing of IFN-γ

A novel iridium(III) complex was prepared and used as a conductor for sensitive and enzyme-free electrochemical detection of interferon gamma (IFN-γ). This assay is based on a dual signal amplification mechanism involving positively charged gold nanoparticles ((+)AuNPs) and hybridization chain reaction (HCR). To construct the sensor, nafion (Nf) and (+)AuNPs composite membrane was first immobilized onto the electrode surface. Subsequently, a loop-stem structured capture probe (CP) containing a special IFN-γ interact strand was modified onto the (+)AuNP surface via the formation of Au-S bonds. Upon addition of IFN-γ, the loop-stem structure of CP was opened, and the newly exposed "sticky" region of CP then hybridized with DNA hairpin-1 (H₁), which in turn opened its hairpin structure for hybridizing with DNA hairpin-2 (H₂). Happen of HCR between H₁ and H₂ thus generated a polymeric duplex DNA (dsDNA) chain. Meanwhile, the iridium(III) complex could interact with the grooves of the dsDNA polymer, producing a strong current signal that was proportional to IFN-γ concentration. Thus, sensitive detection of IFN-γ could be realized with a detection limit down to 16.3 fM. Moreover, satisfied results were achieved by using this method for the detection of IFN-γ in human serum samples.

Luminescent chemosensors by using cyclometalated iridium(iii) complexes and their applications

Luminescent metal complexes have found increasing use in multiple areas of science and technology, including in chemosensing, light-emitting devices and photochemistry. In particular, the use of cyclometalated iridium(iii) complexes as chemosensors has received increasing attention in the recent literature. Phosphorescent metal complexes enjoy a number of advantages (e.g., long-lived phosphorescence, high quantum efficiency and modular syntheses) that render them as suitable alternatives to organic dyes for sensing a variety of analytes. This review describes recent examples of cyclometalated iridium(iii) complexes that act as luminescent chemosensors for cations, anions or small molecules.

Luminescent iridium(iii) complexes as COX-2-specific imaging agents in cancer cells

This is the first application of iridium(iii) complexes as imaging agents for COX-2.

An Aldol Reaction-Based Iridium(III) Chemosensor for the Visualization of Proline in Living Cells

A long-lived aldol reaction-based iridium(III) chemosensor [Ir(ppy)2(5-CHOphen)]PF6 (1, where ppy = 2-phenylpyridine and 5-CHOphen = 1,10-phenanthroline-5-carbaldehyde) for proline detection has been synthesized. The iridium(III) complex 1, incorporating an aldehyde group in N^N donor ligand, can take part in aldol reaction with acetone mediated by proline. The transformation of the sp2-hybridized carbonyl group into a sp3-hybridized alcohol group influences the metal-to-ligand charge-transfer (MLCT) state of the iridium(III) complex, resulting in a change in luminescence in response to proline. The interaction of the iridium(III) complex 1 with proline was investigated by 1H NMR, HRMS and emission titration experiments. Upon the addition of proline to a solution of iridium(III) complex 1, a maximum 8-fold luminescence enhancement was observed. The luminescence signal of iridium(III) complex 1 could be recognized in strongly fluorescent media using time-resolved emission spectroscopy (TRES). The detection of proline in living cells was also demonstrated.