Jianbin Chao

Dual-Site Fluorescent Probe for Visualizing the Metabolism of Cys in Living Cells

Fluorescent probes, as noninvasive tools for visualizing the metabolism of biomolecules, hold great potential to explore their physiological and pathological processes. For cysteine (Cys), however, none of the reported fluorescent probes could image the metabolic processes in living cells. To achieve this goal, we developed a coumarin derivative based on rational design of the dual recognition sites for Cys and its metabolite, SO2. The probe displayed distinct two channels with turn-on fluorescent emission toward Cys and SO2, which were successfully applied for imaging both A549 cells and zebrafish. Further, with reversible fluorescent responses toward Cys, the probe could image the enzymatic conversion of Cys to SO2 in living A549 cells in a ratiometric manner. The present work reports the first probe to image the endogenous generated SO2 without incubation of the SO2 donors.

Thiol-chromene click chemistry: a coumarin-based derivative and its use as regenerable thiol probe and in bioimaging applications.

The synthesis and characterization of a coumarin-chromene (8, 9-dihydro-2H-cyclopenta[b]pyrano[2,3-f]chromene-2,10(7aH)-dione) (1) derivative and its use for thiol chemosensing in water was reported. Experimental details showed 1 acts as a probe for the detection of thiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), whereas amino acids which do not contain thiols induced no changes in UV-vis spectra and fluorescence emission properties of 1. A possible detection mechanism is a nucleophilic attack of thiols to the α,β-unsaturated ketone in 1 that resulted in a fluorescent coumarin derivative. Further studies showed that 1-thiol derivatives can be applied to the design of regenerative chemodosimeters for Cu(2+), Hg(2+) and Cd(2+) in water based on M(n+)-promoted desulfurization and recovery of 1. Furthermore, the optical properties of the probe and its Cys-addition product were theoretically studied. The ability of probe 1 to detect thiols in living cells (HepG2 cells) via an enhancement of the fluorescence was proved. Moreover, the applicability of 1 for the direct determination of biorelevant thiols in a complex matrix such as human plasma was also demonstrated.

Preparation and spectral investigation of inclusion complex of caffeic acid with hydroxypropyl-β-cyclodextrin

The inclusion complexation behavior of caffeic acid (CA) with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was studied by UV-vis, fluorescence spectroscopy and nuclear magnetic resonance spectroscopy (NMR). Experimental conditions including the concentration of HP-beta-CD and media acidity were investigated in detail. The result suggested HP-beta-CD was more suitable for including CA in acidity solution. The binding contants (K) of the inclusion complexes were determined by linear regression analysis and the inclusion ratio was found to be 1:1. The water solubility of CA was increased by inclusion with HP-beta-CD according to the phase-solubility diagram. The spatial configuration of complex has been proposed based on (1)H NMR and two-dimensional (2D) NMR, the result suggested that CA was entrapped inside the hydrophobic core of HP-beta-CD with the lipophilic aromatic ring and the portion of ethylene.

Investigation of the inclusion behavior of chlorogenic acid with hydroxypropyl-β-cyclodextrin.

The inclusion complexation behavior of chlorogenic acid (CGA) with the hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated in both solution and the solid state by UV-vis and fluorescence spectroscopy, infrared spectroscopy (IR), NMR spectroscopy as well as differential scanning calorimetry (DSC). The experimental results indicate that CGA is able to form an inclusion complex with HP-β-CD. The inclusion complex has a stoichiometry of 1:1 and the formation constant was calculated to be 155.7 M(-1). The antioxidant activity of CGA on complexation with HP-β-CD increased as compared to uncomplexed CGA. NMR spectroscopic studies show that the aromatic ring and the vinyl group of CGA are deeply included inside the CD cavity.

A selective fluorescent probe for detection of gold(III) ions and its application to bioimaging

Fluorol Red GK was developed as a on-off fluorescent probe of Au3+ based on Au3+ coordinating to cyano of probe, resulting in fluorescence quenching in a mixed aqueous environment, which was successfully applied to fluorescence imaging in living cells.

Preparation and characterization of the inclusion complex of Baicalin (BG) with β-CD and HP-β-CD in solution: An antioxidant ability study

The formation of the complexes of BG with beta-CD and HP-beta-CD was studied by UV-vis absorption spectroscopy, fluorescence spectra, Phase-solubility measurements and nuclear magnetic resonance spectroscopy (NMR) in solution. The formation constants (K) of complexes were determined by fluorescence method and Phase-solubility measurements. The results showed that the inclusion ability of beta-CD and its derivatives was the order: HP-beta-CD>beta-CD. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of BG with CDs. The antioxidant ability studies of BG and CDs complexes were done. The results obtained indicated that the BG/HP-beta-CD complex was the most reactive form, and then was the BG/beta-CD complex; the last was BG. Special configuration of complex has been proposed on NMR technique.

A Dual Colorimetric/Fluorescence System for Determining pH Based on the Nucleophilic Addition Reaction of an o-Hydroxymerocyanine Dye

Owing to their ability to monitor pH in a precise and rapid manner, optical probes have widely been developed for biological and nonbiological applications. The strategies thus far employed to determine pH rely on two types of processes including reversible protonation of amine nitrogen atoms and deprotonation of phenols. We have developed a novel dual, colorimetric/fluorescence system for determining the pH of a solution. This system utilizes an o-hydroxymerocyanine dye that undergoes a nucleophilic addition reaction that subsequently causes reversible structural changes interconverting a merocyanine to a spirocyanine and a spirocyanine to a spiropyran. It was demonstrated that the dye can be employed to measure the pH of solutions in the 2.5-5.75 and 9.6-11.8 ranges with color changes from yellow to dark blue and then to lavender. Moreover, the fluorescence response associated with the spirocyanine-spiropyran transformation of the dye occurring in alkaline solutions provides a precise method.

Naphthol-based fluorescent sensors for aluminium ion and application to bioimaging

Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1), 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3), have been synthesized. Their recognition abilities for Al(3+) are studied by fluorescence spectra. Coordination with Al(3+) inhibited the CN isomerization of Schiff base which intensely increase the fluorescence of L1-L3. Possessing a suitable space coordination structure, L3 is a best selective probe for Al(3+) over other metal ions in MeOH-HEPES buffer (3/7, V/V, pH=6.6, 25°C, λem=435nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al(3+) to L3. The binding constant Ka of L3-Al(3+) is found to be 1.01×10(6.5)M(-1) in a 1:1 complex mode. The detection limit for Al(3+) is 0.05μM. Theoretical calculations have also been included in support of the configuration of the L3-Al(3+) complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells.

A single fluorescent probe for multiple analyte sensing: efficient and selective detection of CN−, HSO3− and extremely alkaline pH

A simple tailor-made water-soluble broadly emitting (500-650 nm) fluorescent probe 3-methyl-2-(N-ethylcarbazole-3vinyl)-benzothiazolium iodide (IECBT) for the selective and sensitive detection of multiple analytes, including CN-, HSO3 - and extremely alkaline pH, is designed and synthesized via the ethylene bridging of 3-formyl-N-ethylcarbazole and 2,3-dimethyl benzothizolium iodide, which is a useful fluorescent probe for monitoring these analytes at extremely low concentrations quantitatively. CN- and HSO3 - are expected to undergo 1,4-addition reactions with the C-4 atom in the ethylene group of IECBT. This water-soluble fluorescent probe exhibits excellent sensitivity and selectivity toward CN- in DMSO, which also results in a prominent fluorescence ratiometric change and a color change. The high selectivity and sensitivity of IECBT toward HSO3 - and extremely alkaline pH over other coexisting species in water are also observed. The titration experiments show that it features a remarkably large Stokes shift and good stability towards CN-, HSO3 - or extremely alkaline pH with a significant fluorescence turn-off response. Importantly, we demonstrate that IECBT can be used for the real-time sensing and bioimaging of CN-, HSO3 - or extremely alkaline pH in living samples.

Theoretical and experimental study of the inclusion complexes of ferulic acid with cyclodextrins

The inclusion complexation behaviour of ferulic acid (FA) with β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated by UV–vis, fluorescence and 1H NMR spectroscopy. Since the guest may exist in either anionic or neutral form, the experiments were performed at different pH values. The stoichiometry and association constants of the complexes were determined by nonlinear regression analysis. The phase-solubility studies indicated that the water solubility of FA was improved through complexation with β-CD and HP-β-CD. An increase in the antioxidant reactivity was observed when inclusion complexes that FA formed with CDs were studied. Based on the NMR data, the spatial configurations of FA/β-CD and FA/HP-β-CD complexes were proposed, which suggested that FA entered into the cavity of β-CD from the narrow side, with the lipophilic aromatic ring and ethylenic moieties inside the CD cavity, and the –COOH group was close to the wider rim and exposed outside the cavity. A theoretical study of the complexes using molecular modelling gives the results in good agreement with the NMR data.