Hongmin Jia

A highly selective and sensitive ON-OFF-ON fluorescence chemosensor for cysteine detection in endoplasmic reticulum.

A new complex between coumarin-based ligand (CL) and copper ion has been prepared and applied to be an ON-OFF-ON reversible fluorescence chemosensor for the detection of Cys with high sensitivity and specificity. In HEPES buffer, CL displayed high affinity towards Cu(2+) ion over other physiological and environmental metal ions, accompanied with a 98.4% of fluorescence quenching. In the presence of Cys, the detachment of Cu(2+) ion of CL-Cu(2+) ensemble led to the liberation of the fluorophore, CL, and thus fluorescence was recovered. The results of absorption and emission spectroscopy analyses confirmed that the fluorescence turn ON response of CL-Cu(2+) ensemble was selective towards Cys only with high sensitivity (detection of limit, 7.2×10(-7) M). Confocal microscopy studies indicated that the lipophilic CL targets the endoplasmic reticulum (ER) of live cells, where it could be functioned as a fluorescent chemosensor for visualization of Cys in this organelle. Quantitative fluorescence detection of Cys in ER was successfully realized by flow cytometry analysis. The developed chemosensor was further applied to detect Cys in real urine samples with great recoveries ranges from 95.41% to 107.40%.

Fluorescence detection of Fe3+ ions in aqueous solution and living cells based on a high selectivity and sensitivity chemosensor

Although ferric ion (Fe(3+)) performs critical roles in diverse biochemical processes in living systems, its physiological and pathophysiological functions have not been fully explored due to the lack of methods for quantification of Fe(3+) ions in biological system. In this work, a highly sensitive and selective fluorescence chemosensor, L, was developed for the detection of Fe(3+) ions in aqueous solution and in living cells. L was facile synthesized by one step reaction and well characterized by NMR, API-ES, FT-IR, and elementary analysis. The prepared chemosensor displayed excellent selectivity for Fe(3+) ions detection over a wide range of tested metal ions. In the present of Fe(3+) ions, the strong green fluorescence of L was substantially quenched. The 1:1 stoichiometry of the complexation was confirmed by a Jobs plot. The association constant (Ka) of L with Fe(3+) was evaluated using the Benesi-Hildebrand method and was found to be 1.36×10(4) M(-1). The MTT assay determined that L exhibits low cytotoxicity toward living cells. Confocal imaging and flow cytometry studies showed that L is readily interiorized by MDA-MB-231 cells through an energy-dependent pathway and could be used to detect of Fe(3+) ions in living cells.

Reversible and Selective Fluorescence Detection of Histidine Using a Naphthalimide-Based Chemosensing Ensemble.

We described a new ensemble-approach-based chemosensor, NCH-Cu(2+), for highly selective and reversible detection of histidine (His) in aqueous solution and live cells. The ligand NCH exhibited specific binding with Cu(2+) ions over other metal ions, accompanied with a 92.2% fluorescence quenching. The decomplexation of NCH-Cu(2+) ensemble by His led to the liberation of the fluorophore, NCH, and thus the fluorescence was recovered. The specific fluorescence enhancement of NCH-Cu(2+) towards His showed a good linearity with a detection of limit at 70 nm. Quantification of intracellular His at the single cell level was achieved by microscopy and flow cytometry. Besides the UV/Vis and emission titration, reversibility of the NCH-Cu(2+) towards His was further confirmed by imaging and cytometry analysis. In addition, microscopy studies revealed that NCH-Cu(2+) was distributed in the lysosome of live cells, where it could be employed as a fluorescent biosensor for imaging of His at subcellular level.

Synthesis and Application of an Aldazine-Based Fluorescence Chemosensor for the Sequential Detection of Cu2+ and Biological Thiols in Aqueous Solution and Living Cells

A fluorescence chemosensor, 2-hydroxy-1-naphthaldehyde azine (HNA) was designed and synthesized for sequential detection of Cu2+ and biothiols. It was found that HNA can specifically bind to Cu2+ with 1:1 stoichiometry, accompanied with a dramatic fluorescence quenching and a remarkable bathochromic-shift of the absorbance peak in HEPES buffer. The generated HNA-Cu2+ ensemble displayed a “turn-on” fluorescent response specific for biothiols (Hcy, Cys and GSH) based on the displacement approach, giving a remarkable recovery of fluorescence and UV-Vis spectra. The detection limits of HNA-Cu2+ to Hcy, Cys and GSH were estimated to be 1.5 μM, 1.0 μM and 0.8 μM, respectively, suggesting that HNA-Cu2+ is sensitive enough for the determination of thiols in biological systems. The biocompatibility of HNA towards A549 human lung carcinoma cell, was evaluated by an MTT assay. The capability of HNA-Cu2+ to detect biothiols in live A549 cells was then demonstrated by a microscopy fluorescence imaging assay.

A ratiometric fluorescence probe for imaging sulfur dioxide derivatives in the mitochondria of living cells

Although sulfur dioxide (SO2) plays an essential role in several physiological processes, monitoring of intracellular SO2 at subcellular levels remains challenging due to the lack of rapid and sensitive methods for its quantification in a 100% aqueous solution. Herein, a new hemicyanine dyes-based fluorescence probe, NBD-Id, was designed and synthesized for the detection of SO2 derivatives in pure aqueous solution and living cells. By virtue of a specific 1,4-addition reaction of SO32-HSO3- and the polymethine chain of hemicyanine, significant changes in the absorption and fluorescence emission spectra were observed in less than 20 seconds. The ratiometric fluorescence (F467/F593) detection of SO2 derivatives was then obtained with high sensitivity (detection limit 3.6 nM). It was noted that NBD-Id has a specific response towards SO2 derivatives without interference from other anions and biomolecules. Intracellular fluorescence imaging indicated that NBD-Id is cell membrane permeable and mainly distributed within the mitochondria. Therefore, ratiometric fluorescence imaging of SO2 derivatives in the mitochondria of MCF-7 cells was successfully demonstrated.

Selective and sensitive detection of cysteine in water and live cells using a coumarin–Cu2+ fluorescent ensemble

Effective discrimination of cysteine (Cys) from biothiols and other amino acids has gained increasing attention due to the essential roles of this molecule in biological systems. In this work, we report a new strategy for the detection of Cys in aqueous media and live cells using a simple Cu2+ ensemble (L–Cu2+). A coumarin–salicylaldehyde hydrazone fluorescent ligand (L) was initially synthesized and well characterized. L features high affinity towards Cu2+ (Ka = 1.995 × 106 M−1), accompanied by effective quenching of fluorescence in HEPES buffer. The in situ generated chemosensing ensemble, L–Cu2+, is able to specifically respond to Cys over other biothiols and amino acids through a displacement approach. As a result, a remarkable recovery of fluorescence and UV-vis absorption spectra can be observed. L–Cu2+ showed high selectivity and sensitivity towards Cys. The detection limit is estimated to be 15 nM. Using L–Cu2+ as the fluorescent probe, imaging of Cys in live A549 cells was successfully demonstrated.

A highly sensitive electrochemical biosensor for phenol derivatives using a graphene oxide-modified tyrosinase electrode

The fabrication, characterization and analytical performance were investigated for a phenol biosensor based on the covalent bonding of tyrosinase (TYR) onto a graphene oxide (GO)-modified glassy carbon electrode (GCE) via glutaraldehyde (GA). The surface morphology of the modified electrode was studied by atomic force microscope (AFM) and field-emission scanning electron microscopy (FE-SEM). The fabricated TYR/GA/GO/GCE biosensor showed very good stability, reproducibility, sensitivity and practical usage. The catechol biosensor exhibited a wide sensing linear range from 5×10-8M to 5×10-5M, a lower detection limit of 3×10-8M, a current maximum (Imax) of 65.8μA and an apparent Michaelis constant (Kmapp) of 169.9μM.

Rapid Response Fluorescence Probe Enabled In Vivo Diagnosis and Assessing Treatment Response of Hypochlorous Acid-Mediated Rheumatoid Arthritis

Abstract Diagnosis and early assessment of the treatment response of rheumatoid arthritis (RA) necessitates a reliable bioanalytical method for rapid, sensitive, and specific detection of the hypochlorous acid (HOCl) biomarker in inflammatory diseases. Herein, two fluorescence probes, Probe‐1 and Probe‐2 are developed for quantitative monitoring and visualization of inflammatory response–related HOCl levels in vitro and in vivo. In the presence of HOCl, fluorescence “OFF–ON” response is obtained for both the probes as a result of specific HOCl‐triggered C=N bond cleavage reaction. Probe‐1 and Probe‐2 feature rapid response (<4 s), a high degree of sensitivity and selectivity toward HOCl, which allow them to be used for quantification of HOCl in a simulated physiological condition. Using Probe‐2 as the probe, fluorescence imaging and flow cytometry analysis of HOCl levels in lysosome of inflammatory mimic cells, visualization of HOCl generation in endotoxin‐induced inflammation of adult zebrafish and RA of mice are possible. Probe‐2 exhibits high effectiveness for early assessment of the treatment response of HOCl‐mediated RA in mice with an antiarthritic drug, methotrexate (MTX). The results demonstrate that Probe‐2 is a powerful tool for future studies on diagnosis and monitoring treatment efficiency in a broad range of inflammatory diseases, including RA.

Selective detection of inorganic phosphates in live cells based on a responsive fluorescence probe

In this work, we have designed and synthesized a new 4-phenylthiazole-Cu2+ ensemble, L-Cu2+, as a fluorescence probe for the quantitative detection of inorganic phosphates (Pi) in aqueous and live cells. A fluorescent ligand, 2-((4-phenylthiazole-2-imino)methyl)-5-diethylaminophenol (L), was synthesized and its chemical structure was well characterized. L exhibited a high affinity (Ka = 3.27 × 105 M−1) and specificity for Cu2+ ions through a 1 : 1 stoichiometry to form a fluorescence sluggish L-Cu2+ ensemble. This L-Cu2+ ensemble was then employed as a turn-on fluorescence probe for the detection of Pi. Spectroscopic studies revealed that L-Cu2+ possesses excellent tolerance to other common interference anions, and in particular to AMP, ADP, ATP, PPi. The detection limit of L-Cu2+ to Pi was determined to be 0.2 μM. The desirable features of L-Cu2+, such as high specificity and sensitivity and low cytotoxicty, enable its application in the detection of Pi in biological samples. Fluorescence imaging of Pi in live MDA-MB-231 cells was conducted to demonstrate its capability in bioimaging applications. Quantitative analysis of Pi in single cells was then demonstrated using flow cytometry.