An electrochemical detection platform for selective and sensitive voltammetric determination of quercetin dosage in a food supplement by poly(9-(2-(pyren-1-yl)ethyl)-9h-carbazole) coated indium tin oxide electrode

Monitoring of Specific Phytoestrogens by Dedicated Electrochemical Sensors: A Review

Phytoestrogens are non-steroidal estrogens produced from plants that can bind with the human body's estrogenic receptor site and be used as a substitute for maintaining hormonal balance. They are mainly classified as flavonoids, phenolic acids, lignans, stilbenes, and coumestans; some are resocyclic acids of lactones, which are mycotoxins and not natural phytoestrogen. Phytoestrogens have many beneficial medicinal properties, making them an important part of the daily diet. Electrochemical sensors are widely used analytical tools for analysing various pharmaceuticals, chemicals, pollutants and food items. Electrochemical sensors provide an extensive platform for highly sensitive and rapid analysis. Several reviews have been published on the importance of the biological and medicinal properties of phytoestrogens. However, this review provides an overview of recent work performed through electrochemical measurements with electrochemical sensors and biosensors for all the classes of phytoestrogens done so far since 2019.

Sensitive electrochemical determination of quercetin and folic acid with cobalt nanoparticle functionalized multi-walled carbon nanotube

A nanocomposite of cobalt nanoparticle (CoNP) functionalized carbon nanotube (Co@CNT) was prepared and used to modify a glassy carbon electrode (Co@CNT/GCE). Characterization indicates the morphology of Co@CNT is CoNPs adhering on CNTs. With the nano-interface, Co@CNT provides large surface area, high catalytic activity, and efficient electron transfer, which makes Co@CNT/GCE exhibiting satisfactory electrochemical response toward quercetin (QC) and folic acid (FA). The optimum pH values for the detection of FA and QC are 7.0 and 3.0, respectively. The saturated absorption capacity (Γ*) and catalytic rate constant (kcat) of Co@CNT/GCE for QC and FA are calculated as 1.76 × 10-9, 3.94 × 10-10 mol∙cm-2 and 3.04 × 102, 0.569 × 102 M-1∙s-1. The linear range for both FA and QC is estimated to be 5.0 nM-10 μM, and the LODs (3σ/s) were 2.30 nM and 2.50 nM, respectively. The contents of FA and QC in real samples determined by Co@CNT/GCE are comparable with the results determined by HPLC. The recoveries were in the range 90.5 ~ 114% and the total RSD was lower than 8.67%, which further confirms the reliability of the proposed electrode for practical use.

An Enhanced Photosensitive Sensor Based on ITO/MWCNTs@Polymer Composite@BiVO4 for Quercetin Detection

The fact that antioxidants scavenge free radicals in the human body and naturally treat many health problems that will occur in this way has increased the consumption of antioxidant-containing foods. However, consumption of artificially prepared antioxidants could cause cancer. Therefore, antioxidants from natural sources are preferred. Quercetin is an antioxidant present in natural samples. In this article, multi-walled carbon nanotubes (MWCNTs), a polymer composite (PC) consisting of a mixture of 15% (by mass) polystyrene (PST), 15% (by mass) polyacrylonitrile (PAN) and 70% (by mass) polyindole (PIN), and semiconducting BiVO₄ were used to prepare electrodes, and then a photosensitive ITO/MWCNTs@PC@BiVO₄-based sensor was fabricated for quercetin detection. Quercetin was analyzed via the photosensitive ITO/MWCNTs@PC@BiVO₄ sensor in 0.1 M phosphate buffered saline (pH 7.4) solutions including various quercetin concentrations. The constructed quercetin sensor displayed a wide linear response between 10 and 200 μM and a limit of detection of 0.133 μM. The developed photosensitive ITO/MWCNTs@PC@BiVO4 demonstrated a high sensitivity (442 µA mM^-1 cm^-2), good reproducibility (relative standard deviation 3.6%), high selectivity and long-term stability (>49 days) towards quercetin sensing. The photoelectrochemical sensor was then applied to detection of quercetin in black tea as a real-life sample. Our study could lead to the development of novel photosensitive PC polyphenol sensors.

Electrochemical determination of quercetin using glassy carbon electrode modified with WS2/GdCoO3 nanocomposite

A WS₂/GdCoO₃ nanocomposite was successfully prepared using hydrothermal-assisted synthesis. Our prepared WS₂/GdCoO₃ nanocomposite was fabricated on a glassy carbon electrode (GCE) for the detection of quercetin (QCT). The WS₂/GdCoO₃ nanomaterial was characterized by powder XRD, micro-Raman, FT-IR, XPS, FE-SEM, and HR-TEM, which proved that WS₂ nanoplates were finely dispersed on the surface of the GdCoO₃ nanoflakes. The electrocatalytic performance of WS₂/GdCoO₃ was investigated by the EIS technique, and it exhibited a small semi-circle, which confirms that it has a large active surface area and high electrical conductivity. The electrochemical behavior of QCT at the WS₂/GdCoO₃ sensor was explored by using the CV and DPV methods. The proposed electrochemical sensor exhibited excellent electrochemical response toward QCT with a wide linear range of 0.001 to 329 µM, low limit of detection (LOD) of 0.003 µM, and limit of quantification (LOQ) of 0.0101 µM. The sensor also displayed excellent selectivity, sensitivity, reproducibility, and stability. Additionally, the WS₂/GdCoO₃ sensor was utilized for the detection of QCT in apple juice and grape juice samples, and it exhibited good recovery results.

Deep eutectic solvent synthesis of iron vanadate-decorated sulfur-doped carbon nanofiber nanocomposite: electrochemical sensing tool for doxorubicin

Detection of anticancer drug (doxorubicin) using an electrochemical sensor is developed based on a transition metal vanadate's related carbon composite material. With an environmentally friendly process, we have synthesized a metal oxide composite of iron vanadate nanoparticle assembled with sulfur-doped carbon nanofiber (FeV/SCNF). The FeV/SCNF composite was characterized using XRD, TEM, FESEM with elemental mapping, XPS and EDS. In contrast to other electrodes reported in the literature, a much-improved electrochemical efficiency is shown by FeV/SCNF composite modified electrodes. Amperometric technique has been employed at 0.25 V (vs. Ag/AgCl) for the sensitive detection of DOX within a wide range of 20 nM-542.5 μM and it possesses enhanced selectivity in presence of common interferents. The modified electrochemical sensors show high sensitivity of 46.041 μA μM^-1 cm^-2. The newly developed sensor could be used for the determination of doxorubicin in both blood serum and drug formulations with acceptable results, suggesting its feasibility for real-time applications.