A novel peptide-based fluorescent probe for highly selective detection of mercury (II) ions in real water samples and living cells based on aggregation-induced emission effect.

A new fluorescent probe TPE-GHK was synthesized containing a tetrastyrene (TPE) derivative as fluorophore and classical tripeptide (Gly-His-Lys-NH2) as a receptor based on the aggregation-induced emission (AIE) mechanism. TPE-GHK displayed high selectivity and rapid fluorescent "turn-on" response to Hg2+ among other competitive metal ions. The 2:1 complex binding mechanism of TPE-GHK toward Hg2+ was verified by fluorometric titration, Job's plots, and ESI-HRMS spectra. The fluorescent emission showed a good linear response in the range of 0-1.0 µM with the low detection limit of 28.6 nM. Meanwhile, TPE-GHK exhibited the excellent biocompatibility and low toxicity and was successfully applied in monitoring Hg2+ in living CAKI 2 cells, which demonstrated its potential application in environment and biological science. More importantly, TPE-GHK could be used to detect Hg2+ in two real water samples and also was successfully designed as test strips.

Rational development of a peptide-based probe for fluorescence and colorimetric dual-mode detection of Cu2+ and S2- ions: Real application in cell imaging and test strips.

A new dual-mode probe FAM-SSH with fluorescence and colorimetric properties was developed by solid-phase peptide synthesis, comprising 5-carboxy fluorescein (5-FAM) as a fluorophore, and tripeptide (Ser-Ser-His) as a recognition group. FAM-SSH not only displayed highly selective detection of Cu2+ based on fluorescence quenching mode, but also achieved colorimetric recognition of Cu2+ in solution, wherein a color change was observable to the naked eye. Additionally, the FAM-SSH-Cu2+ ensemble was highly selective for S2- over a wide pH range (7.0-12.0), characterized by a fluorescence enhanced response and colorimetric recognition, which was caused by the release of FAM-SSH and the precipitation of CuS. Moreover, the limit of detection (LOD) values for Cu2+ and S2- were 55.5 nM and 31.1 nM, respectively. Results of sample analyses and cell imaging experiments indicated that FAM-SSH has exciting field practicability and good cell permeability, and would be further useful for detection and imaging in environmental systems and living cells. Finally, test strips were produced by immersing them in FAM-SSH solution, thereby creating a method for portable visual detection. More importantly, a smartphone-assisted visual sensing platform was also developed for semi-quantitative Cu2+ and S2- detection with LOD values of 0.48 µM and 1.22 µM, respectively.

Peptide-based colorimetric and fluorescent dual-functional probe for sequential detection of copper(â ¡) and cyanide ions and its application in real water samples, test strips and living cells.

A novel dual-functional peptide probe FLH based on fluorescent "on-off-on" strategy and colorimetric visualization method was designed and synthesized. This new probe exhibited highly selective and rapid detection of Cu2+ with significant fluorescent "turn-off" response, with a visible colorimetric change from yellow to orange. The combination ratio of FLH to Cu2+ (1:1) was determined using ESI-HRMS spectra and Job's plot. The fluorescent emission showed a good linear response (R2 = 0.9986) with a low detection limit of 1.5 nM. In addition, the FLH-Cu2+ complex displayed colorimetric changes and a fluorescent "off-on" response toward CN- over a wide pH range from 7 to 12. This detection behavior was observed within 20 s, with a limit of detection (LOD) for CN- at 12.7 nM. Based on stability and accuracy, FLH was next developed as dual-functional test strips, and was also successfully applied to detect Cu2+ and CN- in two actual water samples. More importantly, the cytotoxicity studies indicated that FLH had good biocompatibility and low toxicity, and was successfully utilized for monitoring Cu2+ and CN- in living cells through fluorescence imaging.

A bifunctional peptide-based fluorescent probe for ratiometric and "turn-on" detection of Zn(II) ions and its application in living cells.

In this work, a bifunctional peptide-based fluorescent probe L containing a tetrapeptide scaffold (Pro-Gly-His-Trp-NH2) and a dansyl group was synthesized using solid phase peptide synthesis (SPPS) technology. As designed, L, based on a FRET mechanism, exhibited high selectivity, excellent ratiometric signals, and fast response to Zn2+ in aqueous solutions at an excitation wavelength of 280 nm. In addition, when excited at 320 nm, L exhibited a fluorescent "turn-on" response towards Zn2+ based on PET mechanism. More importantly, the stoichiometry of L and Zn2+ was determined to be 2:1 by fluorescent titration, Job's plot method, and ESI-MS spectrometry. The association constant for Zn2+ ions was determined to be 6.26 × 108 M-2, while the limit of detection (LOD) of L was estimated as 5.43 nM, which is a much lower value than WHO and EPA guidelines for drinking water. Moreover, L was successfully applied to detect both Zn2+ and Cu2+ in living cells due to good biocompatibility and excellent low toxicity.

Improving Gas-Sensing Performance Based on MOS Nanomaterials: A Review.

In order to solve issues of air pollution, to monitor human health, and to promote agricultural production, gas sensors have been used widely. Metal oxide semiconductor (MOS) gas sensors have become an important area of research in the field of gas sensing due to their high sensitivity, quick response time, and short recovery time for NO2, CO2, acetone, etc. In our article, we mainly focus on the gas-sensing properties of MOS gas sensors and summarize the methods that are based on the interface effect of MOS materials and micro-nanostructures to improve their performance. These methods include noble metal modification, doping, and core-shell (C-S) nanostructure. Moreover, we also describe the mechanism of these methods to analyze the advantages and disadvantages of energy barrier modulation and electron transfer for gas adsorption. Finally, we put forward a variety of research ideas based on the above methods to improve the gas-sensing properties. Some perspectives for the development of MOS gas sensors are also discussed.

Highly selective and sensitive detection of hydrogen sulfide in aqueous medium and live cells using peptide-based bioprobe to mimic the binding sites of the ceruloplasmin for Cu(II) ions.

Hydrogen sulfide (H2S) plays a vital role in biological systems, so it is important to develop new methods for monitoring H2S with high selectively and sensitivity. In this study, we report the efficient solid phase synthesis of a new peptide-based bioprobe L that mimics the Cu(II) binding sites of ceruloplasmin. L exhibits highly sensitive colorimetric and fluorescent "turn off" responses to Cu2+ with high selectively among various metal ions over a broad pH range in 100% aqueous solutions. Interestingly, as a new promising analytical bioprobe, the L-Cu ensemble can monitor H2S by both colorimetric and fluorescent changes, and the limit of detection (LOD) is found to be as low as 14.7 nM. The reversibility experiment indicated that L could be recycled many times as reversible bioprobe. It is worth noting that L could be used to detect Cu2+ and H2S specifically in two real samples. Moreover, L exhibited excellent water-solubility and low biotoxicity even at high concentrations based on MTT study, and cell imaging results indicated that it can be applied to detecting Cu(II) and H2S in living RKO cells monitored by confocal fluorescence microscopy imaging.

A novel fluorescent chemosensor for detection of mercury(II) ions based on dansyl-peptide and its application in real water samples and living LNcap cells.

Mercury is one of the most hazardous pollutants, and mercury pollution is a serious hazard to our environment. Herein, we designed and synthesized a new peptide-based fluorescent chemosensor (L) based on a Fmoc-Lys (Fmoc)-OH backbone conjugated with two Serines and dansyl groups using solid phase peptide synthesis (SPPS) technology. L exhibited highly selective and excellent sensitive detection of Hg2+ ions in 100% aqueous solutions through fluorescence quenching. The chemosensor L forms a 2:1 stoichiometry with high binding constants (4.89×106M-1) and the detection limit for Hg2+ ions of the proposed assay was 7.59nM. In addition, the recovery test results of Hg2+ concentration in actual water samples showed that the quantitative detection of Hg2+ ions can be realized in two water samples. Moreover, L showed low cytotoxicity and excellent membrane permeability in HK2 cells, which has been successfully applied for monitoring Hg2+ ions in living LNCaP cells.