Baocun Zhu

A colorimetric and ratiometric fluorescent probe for thiols and its bioimaging applications

A naphthalimide-based colorimetric fluorescent probe containing a disulfide group was designed and synthesized, which could detect the physiological level of GSH quantitatively by a ratiometric fluorescence method and was successfully applied to the imaging of thiols in living HeLa cells.

A highly selective colorimetric and ratiometric fluorescent chemodosimeter for imaging fluoride ions in living cells

A simple but highly selective colorimetric and ratiometric fluorescent chemodosimeter was designed and synthesized to detect fluoride ions (F(-)) in aqueous solution and living cells by virtue of the strong affinity of F(-) toward silicon.

Ag3PO4/graphene-oxide composite with remarkably enhanced visible-light-driven photocatalytic activity toward dyes in water

Ag(3)PO(4)/graphene-oxide (Ag(3)PO(4)/GO) composite has been synthesized by a liquid phase deposition method, and used for the photodegradation of organic dyes in water under visible light. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, N(2) sorption-desorption, and UV-vis diffuse reflectance spectra. The SEM image indicated that Ag(3)PO(4) particles were mainly distributed on the surface of GO sheets uniformly. DRS analysis revealed that the samples had good visible light response. The photocatalytic activity of Ag(3)PO(4)/GO composite was evaluated by decomposing of dyes (such as methyl orange, rhodamine B) in water under visible or UV-vis light irradiation. The degradation results indicated that the photocatalytic performance of Ag(3)PO(4)/GO was greatly enhanced due to the improved adsorption performance and separation efficiency of photo-generated carriers. The Ag(3)PO(4)/GO composite with GO content of 15 wt.% exhibited superior activity under visible light irradiation. After 50 min of reaction, the degradation ratio of MO was about 86.7%, while RhB solution could be completely degraded within 30 min of reaction. Further study proved that the direct oxidation of pollutants by holes has played a major role in the degradation process. The results of this work would provide a new sight for the construction of visible light-responsive photocatalysts with high performance.

A simple but highly sensitive and selective colorimetric and fluorescent probe for Cu2+ in aqueous media

In this paper, CN-DPA was prepared as an effective colorimetric and fluorescent probe for copper ions (Cu(2+)) in aqueous solution. It exhibits good sensitivity and selectivity for Cu(2+) over other metal ions both in aqueous solution and on a simple colorimetric paper-made test kit. Upon addition of Cu(2+), a remarkable color change from purple to colorless was easily observed by the naked eye, and a fluorescence quenching was also determined. Furthermore, CN-DPA can be used to quantitatively detect Cu(2+). The linear range was 0-5 μM determined by absorption spectrometry. All these selective and sensitive results indicate that CN-DPA could meet the selective requirements for biomedical and environmental application and be sensitive enough to detect Cu(2+) in environmental water samples, even in drinking water, which has a limit of 20 μM defined by the U.S. Environmental Protection Agency.

A highly sensitive ratiometric fluorescent probe with a large emission shift for imaging endogenous cysteine in living cells

A new design strategy for the construction of ratiometric fluorescent probe with a large emission shift was developed. Based on this strategy, a highly selective and sensitive colorimetric and ratiometic fluorescent probe for cysteine (Cys) with a 117 nm red-shifted emission was synthesized and applied to the ratiometric imaging of endogenous Cys in living cells.

Highly Specific and Ultrasensitive Two-Photon Fluorescence Imaging of Native HOCl in Lysosomes and Tissues Based on Thiocarbamate Derivatives

Hypochlorous acid (HOCl) acts as a weak acid distributed mainly in acidic organelle lysosomes of phagocytes and plays a crucial role in the immune defense. The elaborate interrelation between the variations of HOCl levels in lysosomes and different physiological and pathological processes remains unclear. Thus, the accurate determination of lysosomal HOCl in living cells and in vivo is very important. Because of extremely low concentration and difficulty in distinguishing HOCl from OCl- under the physiological environment, it is still a great challenge to specifically monitor the intracellular intrinsic HOCl levels without exogenous stimulation, which impedes an exact understanding of its biological roles. In this paper, based on the electrophilic addition of Cl+ to sulfide moiety, we have developed a two-photon fluorescent probe O-(N-butyl-1,8-naphthalimide)-4-yl-N,N-dimethylthiocarbamate (NDMTC) for the specific determination of HOCl over OCl- and other bioactive molecules. Our results show that NDMTC possesses a detection limit of 7.6 pM, and it is the first fluorescent probe for detecting HOCl at the picomolar level. Furthermore, by introducing an alkylmorpholine group to the NDMTC framework, the lysosome-targetable derivative Lyso-NDMTC was obtained, and its ability to image HOCl in the lysosome organelles was clearly confirmed. Combined with two-photon fluorescence imaging of background suppression and deeper tissue penetration, NDMTC and Lyso-NDMTC were used to successfully visualize intracellular native HOCl and discern tumor tissue in mice. This study offers two perfect fluorescence imaging probes for further investigation of pathological roles of HOCl in various diseases.

Electrochemical immunoassay for carcinoembryonic antigen based on signal amplification strategy of nanotubular mesoporous PdCu alloy.

Interests in using nanoporous metals for biosensing applications have been increasing. Herein, nanotubular mesoporous PdCu (NM-PdCu) alloy is used to fabricate a novel label-free electrochemical immunosensor for cancer biomarker carcinoembryonic antigen (CEA). It operates through physisorption of anti-CEA on NM-PdCu and the mixture of sulfonated graphene sheets (HSO(3)-GS) and thionine (TH) functionalized glassy carbon electrode interface as the detection platform. In this study, chitosan (CS)-PdCu is bound very strongly to carcinoembryonic antibody (anti-CEA), because of the good electron conductivity, high surface area, and good biocompatibility. CS-PdCu is immobilized on electrodes by electrostatic interactions between the negatively charged sulfo group of HSO(3)-GS and the abundant positively charged amino groups of chitosan. TH acts as the redox probe. Under the optimized conditions, the electrochemical immunosensor exhibits a wide working range from 0.01 to 12 ng/mL with a low detection limit of 4.86 pg/mL. The accuracy, reproducibility, and stability of the immunosensor are acceptable. The assay is evaluated for real serum samples, receiving satisfactory results. The nanoporous metal materials-based immunoassay provides a promising approach in clinical application and thus represents a versatile detection method.

A highly selective colorimetric chemodosimeter for fast and quantitative detection of hydrogen sulfide.

Based on the fact that hydrogen sulfide (H(2)S) possesses the smallest steric hindrance among thiols and the SH(-) group adds faster to an electron-poor C=C double bond, we designed and synthesized a tricyanoethylene-derived colorimetric chemodosimeter 1 for the fast and highly selective assay of H(2)S. Chemodosimeter 1 exhibited excellent water-solubility due to the introduction of two hydrophilic hydroxyl groups. Upon the addition of Na(2)S, chemodosimeter 1 showed a fast (complete within 400 s) and robust decrease of the absorption intensity (>97%), accompanied by a color change from red to colorless. Additionally, a linear relationship between absorption intensity and the added Na(2)S concentrations (0-130 μM) was observed in aqueous buffer solution (pH 7.4, 20 mM PBS). Importantly, the proposed paradigm in this paper, adoption of the tricyanoethylene derivative as a recognition receptor to distinguish H(2)S from other thiols and analytes, provides a promising methodology for the design of colorimetric and fluorescent chemodosimeters for fast determination of H(2)S.

A highly selective ratiometric fluorescent probe for 1,4-dithiothreitol (DTT) detection.

A highly selective ratiometric fluorescent probe, which contains an aminonaphthalimide fluorophore and a self-immolative spacer for 1,4-dithiothreitol (DTT) detection was designed and synthesized. The probe displays a 66 nm red-shift of fluorescence emission and the color changes from colorless to jade-green upon reaction with DTT. These properties are mechanistically ascribed to the strong reducing capability of DTT.

A highly specific and ultrasensitive fluorescent probe for basal lysosomal HOCl detection based on chlorination induced by chlorinium ions (Cl

The development of techniques for detecting HOCl at the subcellular level is very important to elucidate its cellular functions. Due to its relatively low concentration, it is still a great challenge to specifically track the basal HOCl in normal cells. In this paper, based on the unique chlorination of HOCl by the initiation of chlorinium ions (Cl+) in an acidic medium, we have developed a simple pH-mediated lysosome-targetable fluorescent probe Lyso-HOCl for the specific detection of HOCl over other bioactive molecules at higher concentration (500 μM). Our results show that Lyso-HOCl possesses a detection limit of 8.0 pM, and can quantitatively detect HOCl at the picomolar level. The ultrasensitive and ultrafast response property of probe Lyso-HOCl offers a good opportunity to monitor the basal HOCl and the fluctuation of endogenous HOCl levels in the lysosomes of macrophages (Raw 264.7 cells), and we thus anticipate that this probe would provide a promising tool for further unraveling the biological functions of HOCl in subcellular lysosomes.