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A new water-soluble fluorescent probe 1 based on hemicyanine dye is designed for selective detection of glutathione (GSH). Probe 1 shows a tremendous colorimetric and ratiometric fluorescence response toward GSH with high selectivity over cysteine/homocysteine. After nucleophilic aromatic substitution reaction with GSH, probe 1 undergoes an intramolecular aldimine condensation that leads to forming a ring, which is accompanied by 107 and 41 nm red-shifts in the absorption and fluorescence spectra, respectively. Subsequent experiments in living cells indicate that probe 1 has a good photostability and response to mitochondrial GSH level in a ratiometric manner. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe O-hNRSel based on tetralin-xanthene fused dye O-hNR was designed and synthesized by introducing 2,4-dinitrobenzenesulfonate functionality. This probe is able to detect selenocysteine (Sec) with rapid response time (2 min) and a large fluorescence enhancement at 624 nm (124-fold). O-hNRSel exhibited selective response to Sec over many other analy and high sensitivity with the detection limit as low as 17 nM. Furthermore, O-hNRSel has been used for fluorescent imaging of Sec in living cells with good biocompatibility. [ABSTRACT FROM AUTHOR]

The highly sensitive and rapid detection and distinction of gram-negative bacteria are essential for the early diagnosis and accurate medical treatment of bacterial infection. In this work, we investigated a new selective and sensitive method of detecting gram-negative bacteria based on a small molecule modified sensor chip by a laser scanning confocal imaging-surface plasmon resonance (LSCI-SPR) system. The small molecule (polymyxin B) strongly interacted with bacteria cell membrane. SPR signals changed with SYTO 9 stained bacteria concentrations, and fluorescence images were recorded at the same time. Results showed that Escherichia coli were distinguished clearly with a limit of detection (LOD) of 1.0 × 10 2 CFU/mL for Escherichia coli . Moreover, a good linear relationship was observed between bacteria concentrations and SPR signals from 1.0 × 10 2 CFU/mL to 1.0 × 10 6 CFU/mL with a linear coefficient R 2 of 0.99146. All these results indicated that this small-molecule modified sensor can be used for quantitative detection of known gram-negative bacteria and qualitative distinction of unknown gram-negative bacteria within 10 min each sample in real-time. [ABSTRACT FROM AUTHOR]

A simple and general procedure is designed for in situ growth of gold nanoparticles (AuNPs) on hydrogen-bond supramolecular structures. The resulting nanocomposites are obtained via a one-pot synthetic method using chloroauric acid (HAuCl 4 ), sodium citrate, melamine (M) and cyanuric acid (CA) as precursors. At room temperature, melamine cyanurate (MCA) is formed immediately by M and CA through hydrogen bond self-assembly, possesses rich nitrogen content (49.4 wt%), and provides evenly dispersed and active sites to anchor and stabilize gold nanoparticles (AuNPs) as an ideal scaffold. The nanocomposites (AuNPs/MCA) exhibit high peroxidase-like activity that can catalyze the oxidation-reduction reaction of H 2 O 2 and peroxidase substrates over a broad pH range, including nearly neutral conditions (pH 5.0–7.4), as well as excellent stability. Combined with glucose oxidase (GO x ), AuNPs/MCA are successfully used for the quantitative determination of blood glucose via one-pot colorimetric assay. This study develops an economic approach for preparation of peroxidase mimetics with high catalytic activity at neutral pH, and well stability, expected to provide guidelines for other types of inorganic/supramolecule nanocomposites, and to broaden their applications in analytical chemistry and environmental science. [ABSTRACT FROM AUTHOR]