An electrochemical aptasensor for methylamphetamine rapid detection by single-on mode based on competition with complementary DNA.

A simple and rapid electrochemical sensing method with high sensitivity and specificity of aptamers was developed for the detection of methylamphetamine (MAMP). A short anti-MAMP thiolated aptamer (Apt) with a methylene blue (MB) probe at 3'-end was immobilized on the surface of a gold electrode (MB-Apt-S/GE). The electrochemical signal appeared when MAMP presenting in the sample solution competed with cDNA for binding with MB-Apt-S. Under optimized conditions, the liner range of this signal-on electrochemical aptasensor for the detection of MAMP achieved from 1.0 to 10.0 nmol/L and 10.0-400 nmol/L. LOD 0.88 nmol/L were obtained. Satisfactory spiked recoveries of saliva and urine were also obtained. In this method, only 5 min were needed to incubate before the square wave voltammetry (SWV) analysis, which was much more rapid than other electrochemical sensors, leading to a bright and broad prospect for the detection of MAMP in biological sample. This method can be used for on-site rapid detection on special occasions, such as drug driving scenes, entertainment venues suspected of drug use, etc.

A self-immolative near-infrared fluorescent probe for identification of cancer cells and facilitating its apoptosis.

Hydrogen sulfide (H2S) plays a significant role in the onset and progression of cancer. It has led to increased interest in its potential as a diagnostic tool owing to its overexpression in cancer. However, research into the anti-cancer activity of H2S, particularly its ability to promote apoptosis, is hindered by the lack of effective detection tools. To gain a comprehensive understanding of the targeted efficacy of H2S in promoting cancer cell apoptosis, we designed and synthesized a self-immolative near-infrared fluorescent diagnostic probe, named YH-NO2. The activation of this self-immolative reaction is dependent on the presence of nitroreductase (NTR) overexpressed in tumor cells. The design of YH-NO2 involves releasing fluorophores through the activated self-immolative reaction for detection, while simultaneously releasing H2S-loaded self-immolative spacers to promote cancer cell apoptosis. Consequently, YH-NO2 achieves a seamless integration of recognizing and promoting cancer cell apoptosis through its self-immolative structure. This dual function allows YH-NO2 to recognize NTR activity in cells under varying hypoxia levels and differentiate between normal cells and cancer cells using imaging technology. Notably, YH-NO2 exhibits remarkable stability in cellular environments, providing controlled and selective H2S release, thereby targeting the elimination of cancer cells through the promotion of apoptosis. Furthermore, in vivo experiments have demonstrated that YH-NO2 can accurately identify tumor tissue and effectively reduce its size by utilizing its apoptosis-promoting properties. These findings not only provide further evidence for the anti-cancer activity of H2S but also offer valuable tools for understanding the complex relationship between H2S and cancer.

Design strategy for an analyte-compensated fluorescent probe to reduce its toxicity.

During biological detection, the toxicity caused by probes to living organisms is neglected. In this study, an analyte-compensated fluorescent probe (NP-SN3) was constructed for the detection of H2S. Through experiments with HepG2 cells and zebrafish embryos and larvae, the NP-SN3 probe showed no significant difference in imaging performance compared with the traditional probe (NP-N3) but exhibited lower detection-induced toxicity in the imaging of liver fibrosis in activated HSC-T6 cells. During the development of zebrafish embryos and continuous administration in rats, NP-SN3 showed a lower death rate, higher hatchability and lower malformation in zebrafish embryos and milder pathological symptoms in stained rat tissues.

A novel H2O2 activated NIR fluorescent probe for accurately visualizing H2S fluctuation during oxidative stress.

Hydrogen sulfide (H2S) is a typical gas signal molecule that plays a vital role in various pathological courses. Despite having the accumulated knowledge on the physiological functions of H2S in many diseases, the process in the measurement of its level in mitochondria during oxidative stress is still far away from the expectation. In this regard, it is great significant to design a fluorescent probe for accurately monitoring the dynamics of H2S during oxidative stress. In this work, we firstly synthesized an oxidative stress activated fluorescence probe QM-RSH for tracking H2S level in mitochondria. It exhibited high selectivity and sensitivity for detecting H2S with lower limit of detection (LOD = 44.6 nM) in the presence of H2O2. QM-RSH can be successfully applied to accurately monitor the fluctuation of H2S level during oxidative stress without interference from other physiological processes in living cells and zebrafish. Therefore, this multifunctional probe QM-RSH has great potential as an image tool in biological research. It also provides a novel strategy for designing fluorescent probe to investigate biomolecular information and signaling pathways under specific physiological conditions.

A water-soluble near-infrared fluorescent probe for monitoring change of hydrogen sulfide during cell damage and repair process.

As a signal molecule involved in autophagy, hydrogen sulfide (H2S) is considered to be essential in the development and treatment of diseases. In order to clarify the complex role of H2S in organism and the participation of H2S in disease process, it is urgently needed to visualize the dynamics of H2S. In this contribution, a water-soluble near-infrared (695 nm emission) self-immolative fluorescent probe CySO3N3 was constructed for H2S detection. The ability of self-immolative strategy to detect H2S was verified to increase the metabolic capacity and reduce the toxicity of probe. This probe can not only be used to detect H2S in living cell and mice, but also shows great potential in detecting H2S changes to monitor cell self-repair during inflammation and myocardial injury.

A novel fluorescent probe with large Stokes shift for accurate detection of HOCl in mitochondria and its imaging application.

Hypochlorous acid (HOCl), mainly generated in mitochondria, plays a critical role in various physiological processes. To better understand the role and function of HOCl in mitochondria, herein, we present the design and synthesis of a Mito-QL reporter for probing the HOCl within mitochondria without other interference generated in living cells. Through the combination of TICT/ICT mechanisms, probe Mito-QL, with large stokes shift (203 nm) and low background fluorescence, exhibited excellent sensitivity (900-fold fluorescence enhancement) and selectivity towards HOCl (LOD = 2.4 nM). The co-location experiments confirmed that probe Mito-QL can firstly localize in the mitochondria and then react with HOCl in mitochondria. Also, the probe is capable of imaging endogenous and exogenous HOCl even the generation of HOCl during the ferroptosis of cells, which is beneficial for more efficient application in biological imaging.

N-quaternization of heterocyclic compound extended the emission to NIR with large Stokes shift and its application in constructing fluorescent probe.

This is great significant to establish a method that extends the small molecules fluorescence emission wavelength to the near-infrared region (NIR) for in vivo imaging. Hence, we firstly reported a novel fluorogenic scaffold QOH that could extend its fluorescence wavelength from (λem = 555 nm) to NIR (λem = 720 nm) with a large Stokes shift (120 nm) by forming its N-quaternization product (QMOH). In addition, the effect of the introduction of substituent at different modification sites and the properties of substituent on the optical properties of QOH were fully discussed by theoretical calculation. To investigate the possibility of QOH as probe construction, the compound Q-SH and QM-R were synthesized and applied to detect H2S and H2O2 in vitro and in vivo, respectively. This study provided an efficient strategy to extend fluorescence emission to NIR and design fluorescence probes with large ratio variation for accurately imaging biomarkers in biological system.

Clean synthesis of RGO/Mn3O4 nanocomposite with well-dispersed Pd nanoparticles as a high-performance catalyst for hydroquinone oxidation.

In this study, a well-dispersed Pd nanoparticle (NP)-supported RGO/Mn3O4 (G/M/Pd) composite was synthesized by a clean synthetic route, where galvanic replacement reaction simply occurred between Mn3O4 and a palladium salt, thereby avoiding the use of harsh reducing and capping agents. The G/M/Pd composite served as a robust catalyst for the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) with H2O2 in an aqueous solution. Oxidation was completed in only 4 min, with a turnover frequency (TOF) of 3613 h-1; this TOF is one hundred times those of previously reported Pd- and Ag-based catalysts. The superior performance was related to the electronic inductive effect between Mn3O4 and Pd NPs, which was verified by density functional theory calculations. Trapping experiments revealed that the oxidation of HQ was considerably related to the ·OH radicals generated from the decomposition of H2O2. In addition, the influencing factors were further investigated, including catalyst and HQ concentrations, solution pH, solvents, and various inorganic and organic interferences. Moreover, the G/M/Pd catalyst exhibits diverse applications for the catalytic oxidation of HQ derivatives with high TOFs.

Catalytic Oxidation of Hydroquinone in Aqueous Solution over Bimetallic PdCo Catalyst Supported on Carbon: Effect of Interferents and Electrochemical Measurement.

Palladium-cobalt alloy nanoparticles were synthesized and dispersed on carbon black support, aiming to have a less expensive catalyst. Catalytic behaviors of PdCo/C catalyst for the oxidation of hydroquinone (HQ) with H2O2 in aqueous solution were evaluated using high-performance liquid chromatography (HPLC). The results revealed that PdCo/C catalyst had better catalytic activity than an equal amount of commercial Pd/C and Co/C catalysts because of the d-band hybridization between Pd and Co. The effects of pH value, solvent, and various interferents including inorganic and organic compounds on the efficiency of HQ oxidation were further investigated. Furthermore, on the basis of mixed potential theory, comprehensive electrochemical measurements such as the open-circuit potential-time (OCP-t) technique and Tafel plot were efficient to assess the catalytic activity of the catalyst, and the results obtained were consistent with those of HPLC measurements. The efficient HQ oxidation was closely associated with the catalytic activity of PdCo nanoparticles because they accelerated the electron-transfer process and facilitated the generation of OH radicals.

One-pot synthesis of graphene-supported monodisperse Pd nanoparticles as catalyst for formic acid electro-oxidation.

To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

Graphene nanosheets-polypyrrole hybrid material as a highly active catalyst support for formic acid electro-oxidation.

A novel electrode material based on graphene oxide (GO)-polypyrrole (PPy) composites was synthesized by in situ chemical oxidation polymerization. Palladium nanoparticles (NPs) with a diameter of 4.0 nm were loaded on the reduced graphene oxide(RGO)-PPy composites by a microwave-assisted polyol process. Microstructure analysis showed that a layer of coated PPy film with monodisperse Pd NPs is present on the RGO surface. The Pd/RGO-PPy catalysts exhibit excellent catalytic activity and stability for formic acid electro-oxidation when the weight feed ratio of GO to pyrrole monomer is 2:1. The superior performance of Pd/RGO-PPy catalysts may arise from utilization of heterogeneous nucleation sites for NPs and the greatly increased electronic conductivity of the supports.

Core-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds.

Silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with controlled silica shell thicknesses were prepared by a modified Stöber method using 20 nm hydrophilic Fe3O4 NPs as seeds. The core-shell NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), and UV-Vis adsorption spectra (UV-Vis). The results imply that NPs consist of a crystalline magnetite core and an amorphous silica shell. The silica shell thickness can be controlled from 12.5 nm to 45 nm by varying the experimental parameters. The reaction time, the ratio of TEOS/Fe3O4, and the concentration of hydrophilic Fe3O4 seeds were found to be very influential in the control of silica shell thickness. These well-dispersed core-shell Fe3O4@SiO2 NPs show superparamagnetic properties at room temperature.

Organic phase synthesis of monodisperse iron oxide nanocrystals using iron chloride as precursor.

Monodisperse iron oxide nanocrystals were synthesized by a simplified method using iron chloride as precursor. In the presence of Cl ions, the as-produced iron oxide nanocrystals preferred a cubic shape with {100} facets exposed. The function of halogens including Cl and Br ions on stabilizing {100} facets of spinel structured iron oxides, rather than the regulation of thermolysis kinetics and surfactants, was found influential on the shape control of nanocubes in this organic phase approach. The synthesis can be also extended for cobalt ferrite nanocubes and cobalt oxide polyhedrons.