A dually functional 4-aminophenylboronic acid dimer for voltammetric detection of hypochlorite, glucose and fructose

Cyanine based ratio fluorescent probe and its application in hypochlorite detection

Hypochlorite (ClO-), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO- or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO- is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO-, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO-, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 μM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

Dual detection and quantification of hypochlorite and sulfite ions via SERS spectroscopy by utilizing the redox reaction of tetramethylbenzidine

We developed a highly efficient, ultra-sensitive, and selective dual detection sensor for hypochlorite (ClO-) and sulfite (SO32-) ions based on surface-enhanced Raman scattering (SERS) spectroscopy. 3,3',5,5'-Tetramethylbenzidine (TMB) is oxidized by ClO- under acidic conditions to diazotized oxTMB that, when electrostatically adsorbed onto Au nanoparticles (NPs), produces a strong Raman signal at 1605 cm-1. Meanwhile, oxTMB is reduced to TMB by SO32-, which significantly reduces the Raman signal. The linear detection range of the proposed sensor is 10-10 to 10-6 M with a detection limit of 59 pM for ClO- and 10-9 to 10-5 M with a detection limit of 5.4 nM for SO32-. In addition, the sensor was successfully applied to detect ClO- and SO32- in water samples.

Selective Ligand-Doped Liquid Crystal-Based Sensing Platform for Detection of ClO- Ions in Aqueous Media

The liquid crystal (LC) detection platform has been fabricated for the detection of hypochlorite ions (ClO^-) in aquatic solutions. In this system, an imine consisting of the ligand (E)-2-((4-(diethylamino)-2-hydroxybenzylidene)amino)-5-methoxybenzenesulfonic acid (MBA) was doped in 4-cyano-4'-pentyl biphenyl as a selecting LC for ClO^-. When immersing the platform in a solution containing ClO^-, hypochlorite appears to react with the imine bond in the MBA, and cause it to cleave, which eventually disrupts the direction of LC and causes a dark-to-bright conversion of the LC image. The detection limit for ClO^- is 0.05 μM. This sensory platform was unresponsive to NO₃ ^-, BrO₃ ^-, CH₃COO^-, CO₃ ^2-, and PO₄ ^3- ions. Our sensing platform also detected ClO^- in piped water. Since this sensory platform is colored under ambient light, it is easy for regular operators, and it can be used as a mobile tool for monitoring water quality anywhere.

A benzothiazole-based fluorescent and colorimetric probe for the detection of ClO- and its application to zebrafish and water sample

A benzothiazole-based fluorescent and colorimetric chemosensor BZD ((E)-2-(benzo[d]thiazol-2-yl)-5-((4-(diethylamino)-2-hydroxybenzylidene)amino)phenol) was applied for detecting ClO^-. BZD showed fluorescence quenching and color variation for ClO^- via oxidative reaction between ClO^- and the imine bond. It could effectively detect ClO^- over various competitive analytes. Detection limit for ClO^- was calculated to be 1.74 μM by fluorescent method and 16.44 μM by colorimetric one, respectively. Additionally, BZD could be utilized for sensing ClO^- in zebrafish, real water sample and paper strip. The photophysical characteristics and sensing mechanism of BZD to ClO^- were studied by fluorescent and UV-visible spectroscopy, NMR titration, and ESI-mass spectrometry.

Simple and Cost-effective Enzymatic Detection of Cholesterol Using Flow Injection Analysis

A flow-injection analytical (FIA) system was developed for the determination of cholesterol concentrations based on enzymatic reactions that occurred in a cholesterol oxidase (CHO_x)-immobilized, fused-silica capillary followed by electrochemical detection. The production of hydrogen peroxide from cholesterol in an enzymatic reaction catalyzed by CHO_x was subsequently oxidized electrochemically at an electrode. Our FlA system demonstrated its cost-effectiveness and utility at an applied potential of 0.6 V (vs. Ag/AgCl), a flow rate of 100 μL/min and, under optimal conditions, the resulting signal demonstrated a linear dynamic range from 50 μM to 1.0 mM with a limit of detection (LOD) of 12.4 μM, limit of quantification (LOQ) of 44.9 μM, and the coefficient of variation of 5.17%. In addition, validation of our proposed system using a reference HDL-cholesterol kit used for clinical diagnosis suggested our FIA system was comparable to commercial kits for the determination of the cholesterol incorporation amount in various aqueous liposomal suspensions. These good analytical features achieved by FIA could make the implementation of this methodology possible for on-line monitoring of cholesterol in various types of samples.

Carbonization and Preparation of Nitrogen-Doped Porous Carbon Materials from Zn-MOF and Its Applications

Nitrogen-doped porous carbon (NPC) materials were successfully synthesized via a Zn-containing metal-organic framework (Zn-MOF). The resulting NPC materials are characterized using various physicochemical techniques which indicated that the NPC materials obtained at different carbonization temperatures exhibited different properties. Pristine MOF morphology and pore size are retained after carbonization at particular temperatures (600 °C-NPC600 and 800 °C-NPC800). NPC800 material shows an excellent surface area 1192 m2/g, total pore volume 0.92 cm3/g and displays a higher CO2 uptake 4.71 mmol/g at 273 k and 1 bar. Furthermore, NPC600 material displays good electrochemical sensing towards H2O2. Under optimized conditions, our sensor exhibited a wide linearity range between 100 µM and 10 mM with a detection limit of 27.5 µM.

Simple aminophenol-based electrochemical probes for non-enzymatic, dual amperometric detection of NADH and hydrogen peroxide

Non enzymatic detection of NADH and H₂O₂ is of practical significance for both environmental and biological prospective. However, there is no simple, straight forward electrochemical sensor available for sensing of them in real samples. Addressing this challenge, we report a simple stimuli responsive aminophenol, pre-anodized screen printed carbon electrode (SPCE*/AP) based electrochemical probes for dual detection of NADH and H₂O₂. Aminophenol prepared and adsorbed on the electrode from aminophenylboronic acid via boronic acid deprotection with H₂O₂. The SPCE*/AP fabricated with this process was characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), Raman spectroscopy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). Amperometric detection results showed that SPCE*/AP electrodes exhibited linearity from 50 µM to 500 µM and from 200 µM to 2 mM with a detection limit (S/N = 3) of 4.2 µM and 28.9 µM for NADH and H₂O₂, respectively. Excellent reproducibility and selectivity for NADH and H₂O₂ were observed for this electrochemical platform. In addition, the matrix effect was investigated further using the same technique to analyze NADH and H₂O₂ in human urine samples, human serum samples, cell culture medium (containing 10% fetal bovine serum, FBS), and environmental water samples (tap water and rain water). Also, the present sensor demonstrated promising outcomes with living cells (normal cells and cancer cells).

An Imidazo[1,5-α]Pyridine-Based Fluorometric Chemodosimeter for the Highly Selective Detection of Hypochlorite in Aqueous Media

A new fluorometric chemodosimeter 2-amino-3-(((E)-3-(1-phenylimidazo[1,5-α]pyridin-3-yl)benzylidene)amino)maleonitrile (BPI-MAL) has been designed and synthesized for sensing hypochlorite. BPI-MAL showed a selective turn-on fluorescence for ClO^- through hypochlorite-promoted de-diaminomaleonitrile reaction. It also could detect ClO^- in the presence of various competitive anions including reactive oxygen species. Interestingly, sensor BPI-MAL was successfully applied as a fluorescent test kit for ClO^- determination. The sensing property and mechanism of BPI-MAL toward ClO^- were studied by fluorescence and UV-vis spectroscopy, NMR titration and DFT calculations.

Porous Ni3N nanosheet array as a catalyst for nonenzymatic amperometric determination of glucose

A glassy carbon electrode was modified with an array of porous Ni₃N nanosheets (Ni₃N NA) and studied for its use in non-enzymatic electrochemical detection of glucose. The morphology and structure of the Ni₃N NA were characterized by scanning electron microscopy and X-ray diffraction. Electrochemical studies demonstrated that the Ni₃N NA acts as an efficient catalyst for the electro-oxidation of glucose at pH 13, best at a working voltage of 0.55 V (vs. Ag/AgCl). Figures of merit include (a) high sensitivity (39 μA·mM^-1·cm^-2), (b) a low limit of detection (0.48 μM), and (c) a linear range that extends from 2 μM to 7.5 mM. The sensor was applied to the determination of glucose levels in human serum, and satisfactory results were obtained. Graphical abstract Nonenzymatic electrochemical glucose sensor based on porous Ni₃N nanosheet array. The arrow indicates the successive addition of glucose standard solutions.