Ultrasensitive voltammetric detection of an antimalarial drug (amodiaquine) at a disposable and low cost electrode

ZrS2 Nanoparticles Embedded in Chitosan-Based Hydrogel for the Electrochemical Detection of Antimalarial Drug Amodiaquine in Serum Samples

In this study, we report the synthesis of ZrS2 nanoparticles embedded in a chitosan-based hydrogel (ZrS2/CS hydrogel) for the electrochemical detection of amodiaquine (ADQ). The ZrS2 nanoparticles are synthesized via a hydrothermal synthesis technique. Morphologically, transmission electron microscopy images show that the ZrS2 nanoparticles agglomerated to form nanoclusters. Scanning electron microscopy images reveal the porous interconnected structure of the stacked hydrogel layer with ZrS2 nanoparticles that have a high surface area and electrochemically active sites. These ZrS2 nanoparticles embedded in the hydrogel enhanced the high electron transport during the redox process. Differential pulse voltammetry is employed to electrochemically detect ADQ in a wide linear range of 0.02 nM to 2 μM. The sensitivity of ADQ is calculated to be 1.138 μA/nM with a limit of detection of 0.4 nM and a limit of quantification of 1.33 nM. The possible mechanism behind the enhanced performance can be ascribed to the electrochemical oxidation of ADQ, its corresponding quinone-imine, and the improved interaction between the electrode and electrolyte solution, leading to enhanced electron transfer and more stable signals for electrochemical sensing. The sensor developed here has a highly selective response toward ADQ over other interferents such as NaCl, urea, uric acid, glucose, ascorbic acid, and dopamine. In simulated human serum, the sensor shows a recovery rate from 98.58 to 100.62%, suggesting its potential in developing electrochemical sensors. The repeatability and reproducibility results of the ZrS2/CS hydrogel show excellent consistent results, with relative standard deviations of 3.41 and 3.46%, respectively, further affirming the reliability of the sensor. This approach opens up future research directions for detecting various analytes in point-of-care and other biomedical devices.

Low-Cost and Portable Biosensor Based on Monitoring Impedance Changes in Aptamer-Functionalized Nanoporous Anodized Aluminum Oxide Membrane

We report a low-cost, portable biosensor composed of an aptamer-functionalized nanoporous anodic aluminum oxide (NAAO) membrane and a commercial microcontroller chip-based impedance reader suitable for electrochemical impedance spectroscopy (EIS)-based sensing. The biosensor consists of two chambers separated by an aptamer-functionalized NAAO membrane, and the impedance reader is utilized to monitor transmembrane impedance changes. The biosensor is utilized to detect amodiaquine molecules using an amodiaquine-binding aptamer (OR7)-functionalized membrane. The aptamer-functionalized membrane is exposed to different concentrations of amodiaquine molecules to characterize the sensitivity of the sensor response. The specificity of the sensor response is characterized by exposure to varying concentrations of chloroquine, which is similar in structure to amodiaquine but does not bind to the OR7 aptamer. A commercial potentiostat is also used to measure the sensor response for amodiaquine and chloroquine. The sensing response measured using both the portable impedance reader and the commercial potentiostat showed a similar dynamic response and detection threshold. The specific and sensitive sensing results for amodiaquine demonstrate the efficacy of the low-cost and portable biosensor.

Highly sensitive voltammetric determination of the fungicide fenhexamid using a cost-effective and disposable pencil graphite electrode

A differential pulse voltammetric (DPV) method is proposed for the highly sensitive determination of fenhexamid (FHX) based on both electrooxidation and electroreduction processes using a disposable and cost-effective pencil graphite electrode (PGE). The electrochemical oxidation and reduction mechanisms of FHX at the PGE were elucidated by recording cyclic voltammograms at various pH values of Britton-Robinson buffer (BRB) solutions at a scan rate of 50 mV s-1 and different scan rate values in the range 10-400 mV s-1 at selected pH of BRB (pH 2.0). Differential pulse voltammograms recorded under optimized conditions revealed an oxidation peak of FHX around + 0.65 V and a reduction peak of FHX around + 0.45 V. The DPV analysis of FHX revealed two linear ranges: 0.001-0.01 µmol L-1 and 0.01-5.0 µmol L-1 for the anodic peak, and 0.001-0.1 µmol L-1 and 0.1-5.0 µmol L-1 for the cathodic peak. The limits of detection were 0.34 nmol L-1 and 0.32 nmol L-1 for the anodic and cathodic peaks, respectively. The proposed methodology demonstrated satisfactory selectivity, as selected pesticides, certain electroactive compounds, and cationic species tested did not interfere with the voltammetric determination of FHX, particularly during its reduction. The recovery results, showing values close to 100% obtained from the analysis of real samples spiked with FHX, indicated that this methodology can accurately determine FHX in water and soil samples.

Voltammetric Determination of Favipiravir Used as an Antiviral Drug for the Treatment of Covid-19 at Pencil Graphite Electrode

This work describes the sensitive voltammetric determination of favipiravir (FAV) based on its reduction for the first time with a low-cost and disposable pencil graphite electrode (PGE). In addition, the determination of FAV was also performed based on its oxidation. Differential pulse (DP) voltammograms recorded in 0.5 M H2SO4 for the reduction of FAV show that peak currents increase linearly in the range of 1.0 to 600.0 μM with a limit of detection of 0.35 μM. The acceptable recovery values (98.9-106.0 %) obtained from a pharmaceutical tablet, real human urine, and artificial blood serum samples spiked with FAV confirm the high accuracy of the proposed method.

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.