Nanohybrid sensor for simple, cheap, and sensitive electrochemical recognition and detection of methylglyoxal as chemical markers

Subtle adjustment of the cyclic potential on electro-activated glassy carbon electrodes for sensitive sensing of methyl parathion

Facile electro-activated glassy carbon electrodes (e-GCEs), which are prepared in electrolyte solution with a certain potential for a few seconds, have been verified to improve analytical performance toward not a few electro-active molecules recently. Nevertheless, how and why the potential plays an important role is not clear, and has even not received enough consideration. In this paper, we found that the mode and the range of applied potential significantly impacted the sensitivity of methyl parathion (MP), which is a typical pesticide with the electro-active group of -NO2. Compared with constant potential, the e-GCE with cyclic potential provided a much more stable baseline during MP detection. Additionally, the electro-oxidation peak current of MP at around -0.1 V on it was higher than another changeable potential (constant current). What's more interesting, with cyclic potential for 50 segments from -2 to 1.5 V, the peak current value increased by 30 times in comparison with a bare GCE, but only 2 times from -2 to 1 V. Then after systematic investigation including structures of the electrode surface and functional groups, we speculated that the produced group of O-CO in the process of activation and remaining groups of C-O and CO on the bare GCE surface are beneficial for adsorbing MP molecules leading to enhanced peak current. Employing the proposed e-GCE, the limit of detection of MP reached 0.015 μM and the reproducibility was perfect. This work elucidates the potent impact of electro-activation potential parameters on electroanalysis behaviors.

Photo-Enhanced Chemo-Transistor Platform for Ultrasensitive Assay of Small Molecules

Compared with traditional assay techniques, field-effect transistors (FETs) have advantages such as fast response, high sensitivity, being label-free, and point-of-care detection, while lacking generality to detect a wide range of small molecules since most of them are electrically neutral with a weak doping effect. Here, we demonstrate a photo-enhanced chemo-transistor platform based on a synergistic photo-chemical gating effect in order to overcome the aforementioned limitation. Under light irradiation, accumulated photoelectrons generated from covalent organic frameworks offer a photo-gating modulation, amplifying the response to small molecule adsorption including methylglyoxal, p-nitroaniline, nitrobenzene, aniline, and glyoxal when measuring the photocurrent. We perform testing in buffer, artificial urine, sweat, saliva, and diabetic mouse serum. The limit of detection is down to 10^-19 M methylglyoxal, about 5 orders of magnitude lower than existing assay technologies. This work develops a photo-enhanced FET platform to detect small molecules or other neutral species with enhanced sensitivity for applications in fields such as biochemical research, health monitoring, and disease diagnosis.

Electrochemical approaches based on micro- and nanomaterials for diagnosing oxidative stress

This review article comprehensively discusses the various electrochemical approaches for measuring and detecting oxidative stress biomarkers and enzymes, particularly reactive oxygen/nitrogen species, highly reactive chemical molecules, which are the byproducts of normal aerobic metabolism and can oxidize cellular components such as DNA, lipids, and proteins. First, we address the latest research on the electrochemical determination of reactive oxygen species generating enzymes, followed by detection of oxidative stress biomarkers, and final determination of total antioxidant activity (endogenous and exogenous). Most electrochemical sensing platforms exploited the unique properties of micro- and nanomaterials such as carbon nanomaterials, metal or metal oxide nanoparticles (NPs), conductive polymers and metal-nano compounds, which have been mainly used for enhancing the electrocatalytic response of sensors/biosensors. The performance of the electroanalytical devices commonly measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in terms of detection limit, sensitivity, and linear range of detection is also discussed. This article provides a comprehensive review of electrode fabrication, characterization and evaluation of their performances, which are assisting to design and manufacture an appropriate electrochemical (bio)sensor for medical and clinical applications. The key points such as accessibility, affordability, rapidity, low cost, and high sensitivity of the electrochemical sensing devices are also highlighted for the diagnosis of oxidative stress. Overall, this review brings a timely discussion on past and current approaches for developing electrochemical sensors and biosensors mainly based on micro and nanomaterials for the diagnosis of oxidative stress.

α-Dicarbonyl compounds in food products: Comprehensively understanding their occurrence, analysis, and control

α-Dicarbonyl compounds (α-DCs) are readily produced during the heating and storage of foods, mainly through the Maillard reaction, caramelization, lipid-peroxidation, and enzymatic reaction. They contribute to both the organoleptic properties (i.e., aroma, taste, and color) and deterioration of foods and are potential indicators of food quality. α-DCs are also important precursors to hazardous substances, such as acrylamide, furan, advanced lipoxidation end products, and advanced glycation end products, which are genotoxic, neurotoxic, and linked to several diseases. Recent studies have indicated that dietary α-DCs can elevate plasma α-DC levels and lead to "dicarbonyl stress." To accurately assess their health risks, quantifying α-DCs in food products is crucial. Considering their low volatility, inability to absorb ultraviolet light, and high reactivity, the analysis of α-DCs in complex food systems is a challenge. In this review, we comprehensively cover the development of scientific approaches, from extraction, enrichment, and derivatization, to sophisticated detection techniques, which are necessary for quantifying α-DCs in different foods. Exposure to α-DCs is inevitable because they exist in most foods. Recently, novel strategies for reducing α-DC levels in foods have become a hot research topic. These strategies include the use of new processing technologies, formula modification, and supplementation with α-DC scavengers (e.g., phenolic compounds). For each strategy, it is important to consider the potential mechanisms underlying the formation and removal of process contaminants. Future studies are needed to develop techniques to control α-DC formation during food processing, and standardized approaches are needed to quantify and compare α-DCs in different foods.

Detection and electrocatalytic mechanism of zearalenone using nanohybrid sensor based on copper-based metal-organic framework/magnetic Fe3O4-graphene oxide modified electrode

A novel and simple strategy was proposed for the determination of ZEA in breakfast cereal, maize powder and rice flour using an electrochemical nanohybrid sensor based on copper-based metal-organic framework (Cu-MOF)/magnetic Fe₃O₄-graphene oxide (Fe₃O₄-GO) modified electrode fabricated by the layer-by-layer assembled technique. The synthesized Cu-MOF with high porosity favorably improved the effective surface area and the analytical performance of nanohybrid sensing electrode. The crafted sensor has large surface area, high electron transfer, and satisfactory efficiency. ZEA was electrochemically detected in a wide linear range from 159.2 to 2865.2 ng mL^-1 with LOD of 23.14 ng mL^-1 under the optimal conditions. Moreover, the electrocatalytic mechanism of ZEA oxidation was proposed by density functional theory (DFT). A favorable energetic interaction was presented when Cu-MOF adsorbed on Fe₃O₄-GO, and a small new band appeared on the Fermi level energy (E_f) that facilitated the electron transfer between bands.

Nitrogen, phosphorus co-doped hollow porous carbon microspheres as an oxidase-like electrochemical sensor for baicalin

The extraordinary properties and unique structure of porous carbon has rapidly turned into a new favorite in the development and application of high-performance electrocatalytic sensor. Nitrogen, phosphorus co-doped hollow porous...

An electrochemical sensor with a copper oxide/gold nanoparticle-modified electrode for the simultaneous detection of the potential diabetic biomarkers methylglyoxal and its detoxification enzyme glyoxalase

Highly sensitive electro-oxidation of the MGO and GLO biomarkers at the CuO/Au/GCE sensor employing the AdSDPV method.