Jinxin Huang

A dual-site fluorescent probe for direct and highly selective detection of cysteine and its application in living cells

Monitoring the concentration of cysteine (Cys) in living creature is of significance in disease diagnosis because abnormal concentration of cysteine are involved in a variety of diseases. Herein a novel fluorescent probe HC with high- and low- sensitivity sites for the detection of cysteine was designed and synthesized. The acrylate group was employed as the high sensitivity site, which can be selectively and fast removed by Cys. And the α,β-unsaturated ketone can react with Cys as the low sensitivity site. Our probe HC can remarkably exhibit a turn-on signal to the low concentration range of Cys and a ratiometric response to the high concentration range of Cys. Furthermore, kinetic studies showed that the probe possesses a rapid response to Cys and highly selective property to differentiate Cys from glutathione (GSH) and homocysteine (Hcy). Moreover, it has been successfully applied for detection of cysteine in living cells in terms of its excellent cell permeability and low cytotoxicity. Accordingly, these desirable characteristics may suggest that probe HC could be applied for discriminative sensing of intracellular Cys, giving it potential for biological applications.

Rational design of a novel mitochondrial-targeted near-infrared fluorescent pH probe for imaging in living cells and in vivo

Intracellular pH plays an important role in cellular behaviors and pathological conditions. Sensing and monitoring intracellular pH changes in living systems by near-infrared fluorescence probes is essential. In this study, a novel mitochondrial-targeted near-infrared fluorescent pH probe was rationally designed and synthesized. Based on the protonation/deprotonation of the hydroxyl and sulfonic group on the hemicyanine skeleton, probe NIR-F1 exhibits excellent sensitivity and selectivity to pH. Moreover, NIR-F1 could target the mitochondria and monitor pH changes in living cells and living mice. The results indicate that NIR-F1 is a reliable NIR fluorescent pH probe in vivo, giving it potential for biological applications.

Cyanine-based NIR fluorescent probe for monitoring H 2 S and imaging in living cells and in vivo

As a critical gaseous signaling molecule, H2S is involved in various biological processes. To deeper study the physiological and pathological roles of H2S, convenient and efficient detection techniques for endogenous H2S in vivo are still in urgent demand. Herein, we reported a new turn-on Near-infrared (NIR) fluorescence probe NIR-H2S based on thiolysis reactions for detection of H2S. The probe possessed many excellent properties including high sensitivity and selectivity, good cell-membrane permeability, and low cytotoxicity. In vitro, NIR-H2S showed a 58-fold fluorescence enhancement when reacted with H2S in a buffer and displayed a good linear relationship (r = 0.9925) in a rather wide concentration range of H2S (0-500 μM). Furthermore, NIR-H2S was successfully employed in monitoring endogenous H2S induced by D-Cys in living cancer cells and mice. These results indicated that NIR-H2S had great potentiality in detecting cellular H2S in living animals and being applied to cancer diagnosis.

Colorimetric detection of cholic acid based on an aptamer adsorbed gold nanoprobe

Cholic acid (CA) has been proved as an effective clinical biomarker for disease diagnosis and treatment monitoring. However, traditional CA detection methods are tedious, time-consuming and expensive, and the results cannot be visualized. Herein, we present a facile, low-cost, fast and label-free biosensor platform based on a CA aptamer (48 nt) modified gold nanoprobe for CA detection. CA can bind with the surface-adsorbed CA aptamers competitively and detach the aptamer from the gold nanoparticles (Au NPs). Au NPs modified with aptamers of different densities will grow into morphologically varied nanostructures. The result can be observed visibly and quantified easily with the localized surface plasmon resonance (LSPR) spectra. The detection limit (LOD) was 1 μM, which was lower than the existing colorimetric detection methods based on Au NPs. Furthermore, the affinity between CA and 48 nt aptamer was verified for the first time by MicroScale Thermophoresis (MST) technology.

Novel dual-site fluorescent probe for monitoring cysteine and sulfite in living cells

Fluorescent probes have been considered to be efficient tools for the visualization of physiological and pathological processes. Herein, a dual-site fluorescence probe denoted as LC-1 was developed for the detection of cysteine (Cys) and its metabolite SO32−. The probe was shown to be highly sensitive to Cys and SO32− with a turn-on mode fluorescence signal through two emission channels under excitations at wavelengths of 320 nm and 440 nm. Notably, the LC-1 probe was also observed to be satisfactorily sensitive to Cys and SO32− in the presence of other amino acids and reactive oxygen species (ROS). Meanwhile, LC-1 was shown to have low cytotoxicity and was successfully applied for imaging the metabolism of Cys in living cells.

A highly sensitive fluorescent probe for fast recognization of DTT and its application in one- and two-photon imaging

As a widely used reducing agent, 1, 4-dithiothreitol (DTT) plays important roles in the fields of biology, biochemistry, and biomedicine. The development of facile and fast methods for DTT detection is urgent and necessary. In this article, we rationally constructed a novel two-photon fluorescent probe 6-(methylsulfinyl)-2-phenyl-1H-benzo[de]isoquinoline-1,3(2 H)-dione (NC-DTT) for detecting DTT, which employed the 1,8-naphthalimide and sulfoxide as the fluorophore and receptor unit respectively. The sulfoxide group in probe NC-DTT can be reduced by DTT to compound 6-(methylthio)-2-phenyl-1H-benzo[de]isoquinoline-1,3(2 H)-dione (NC), which could emit strong fluorescence with large Stokes shift presumably due to the enhanced intramolecular charge transfer (ICT). This probe responded to DTT quickly (within 1000 s) and showed satisfactory selectivity. A good linearity between fluorescence intensity and the concentration of DTT in the range of 0 - 700 μM was observed, and the detection limit towards DTT was 1.4 × 10-7 M. Furthermore, the probe was successfully employed in one- and two-photon imaging of DTT in HepG2 cells with low cytotoxicity.

A novel one- and two-photon fluorescent probe induced by light for selective imaging of Cys in living cells and tissues

A novel one- and two-photon fluorescent probe based on a photoreaction was developed for the detection of cysteine (Cys). After it was reacted with Cys and illuminated by light, a strong turn-on fluorescence was observed at the excitation of 390 nm. The probe IC-2 was well tolerated at physiological pH conditions and exhibited a fast response rate to Cys within 10 min. Moreover, the probe IC-2 displayed high selectivity towards Cys among other amino acids and metal ions. Fluorescence response studies suggested that the limit of detection of IC-2 was calculated as 2.6 × 10-8 M. An MTT assay demonstrated that IC-2 had good cell permeability and low cytotoxicity to HepG2 cells. Notably, IC-2 was successfully applied in one- and two-photon fluorescence imaging for Cys in living cells and tissues.