A highly dispersed multi-walled carbon nanotubes and poly(methyl orange) based electrochemical sensor for the determination of an anti-malarial drug: Amodiaquine

Electrochemical Determination of N‑Guanylurea Dinitramide (FOX-12) Using a Poly(Methyl Orange)-Modified Carbon Nanotube Electrode

This study introduces a novel electrochemical method and a sensor electrode designed for the first time to enable the selective and sensitive quantification of N-guanylurea dinitramide (FOX-12) via square-wave voltammetry (SWV). A glassy carbon (GC) electrode was surface-modified to create the new working electrode using poly-(methyl orange: MO), which was altered by electropolymerizing the acid/base indicator MO using cyclic voltammetry and dripping well-dispersed multiwalled carbon nanotubes solution onto the electrode surface. The current intensity was correlated to the concentration of FOX-12, and the calibration line was built between 10 and 100 mg L-1 of FOX-12. The limit of detection (LOD) and the limit of quantitation (LOQ) for FOX-12 were 1.5 mg L-1 and 5.0 mg L-1, respectively, and its distinctive reduction peak potential was determined to be around -1.25 V. Additionally, the modified GC/MWCNTs/pMO electrode was effectively used to measure FOX-12 in the presence of synthetic and real mixtures of energetic substances. Furthermore, FOX-12 (50 mg L-1) was quantitatively recovered at 40-fold concentrations of common soil ions and 10-fold concentrations of camouflage materials. The proposed method was applied to clay soil samples polluted with FOX-12 and validated against an HPLC method using the statistical t- and F-tests.

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.

Electrochemical investigation of an anticancer drug 5-Fluorouracil in the presence of Theophylline using low-cost and disposable poly(GLY) modified pencil graphite electrode

Herein this study, a facile, efficient and disposable electrochemical sensor has been prepared by electropolymerization of glycine (poly(GLY)) on the surface of pencil graphite electrode (PGE). The surface topology of the equipped poly(GLY) modified pencil graphite electrode (poly(GLY)/PGE) and bare pencil graphite electrode (BPGE) has been characterized by the scanning electron microscopy (SEM) combined with energy dispersive x-ray analysis (EDX) and charge transfer behaviour was measured by electron impedance spectroscopy (EIS) method. The voltammetric behaviour of anticancer, 5-fluorouracil (5-FU) in the presence of theophylline (THP) has been carried out in 0.1 M phosphate buffer solution (PBS) of physiological pH 7.0 using different techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). The proposed poly(GLY)/PGE shows augmented peak current for 5-FU at lower potential side over the BPGE due to the electrocatalytic behaviour of modifier layers wrapped on the electrode surface. The kinetic behaviour of 5-FU at modified electrode surface was studied by varying different parameters such as pH, scan rate and concentration study in 0.1 M PBS used as a supporting electrolyte. The limit of detection (LOD) for 5-FU was attained using DPV method with different concentrations (1.0-13.0 μM) and it was found to be 0.012 μM. The possible electrochemical reaction of 5-FU was proposed and it was incorporated by two electrons and two protons mechanism at modified electrode surface. The voltammetric response of poly(GLY)/PGE towards the determination of 5-FU was unaffected in the presence of some excipients in addition to the remarkable stability and reproducibility. The applicability of the proposed sensor has been performed by real sample investigation of 5-FU with a substantial percentage of recovery results in all optimized conditions.

Conducting dyes as electro-active monomers and polymers for detecting analytes in biological and environmental samples

Currently, electrochemical sensors are regarded as an efficient tool for the biological and environmental sensing. Electrochemical sensors, such as voltammetric, amperometric, and impedimetric sensors, have gained great attention due to their simplicity, sensitivity, and selectivity. The performance of these electrochemical sensors could be enhanced by surface engineered nano/micro structured materials with conducting dyes/redox species. In this review, a great focus has been put on the redox-active dyes because of their electronic, optical, electrochromic, and conductivity properties. The mechanisms of oxidation and subsequent polymerization of different redox-active dyes at the surface of electrodes have been studied. Additionally, their role in catalyzing the oxidation or reduction of the target analytes at the surfaces of electrodes has also been highlighted. The redox-active dyes were used as electrochemical probes for detecting various analytes in biological and environmental samples. Overall, redox-active dyes are considered promising conducting polymers for the assessment of many analytes such as drugs, pesticides, surfactants, and heavy metal ions.

An electrochemical sensor for the voltammetric determination of artemisinin based on carbon materials and cobalt phthalocyanine

An electrochemical sensor for the determination of artemisinin has been developed based on a glassy carbon electrode modified with hybrid nanocomposites of cobalt phthalocyanine, graphene nanoplatelets, multi-walled carbon nanotubes and ionic liquids (IL). To improve the sensitivity and selectivity of the sensor, cobalt phthalocyanine (CoPc) was used as an effective redox mediator to promote and catalyze the artemisinin reduction. Furthermore, the graphene nanoplatelets and multi-walled carbon nanotubes were used as excellent conducting supporting materials to improve the sensitivity of the electrochemical sensor. Moreover, IL with a surface charge was also employed to prevent aggregation of the graphene nanoplatelets and multi-walled carbon nanotubes. The analytical signal was generated from the reduction of Co(III)Pc generated by artemisinin. The proposed electrochemical sensor was applied to the detection of artemisinin using differential pulse voltammetry and provided a signal with wide linearity ranging from 1.5-60 μM and 60-600 μM and a detection limit of 0.70 μM (3SD/m). Furthermore, the proposed sensor displayed good repeatability and reproducibility of 2.9-3.0 and 3.1-4.4% RSD, respectively. Applications of the sensor to drug and plant samples demonstrated accuracy in a range of 105-116% recoveries. In addition, the results were in good agreement with those obtained from the HPLC method as a reference technique. Thus, the proposed electrochemical sensor provides a new alternative platform for sensitive and selective determination of artemisinin in the analysis of pharmaceuticals with good precision and accuracy.

A review on analytical methods with special reference to electroanalytical methods for the determination of some anticancer drugs in pharmaceutical and biological samples

It is widely accepted that cancer, the second leading cause of death, is a morbidity with big impacts on the global health. In the last few years, chemo-therapeutic treatment continually induces alone most lengthy consequents, which is extremely harmful for the physiological and psychological health of the patients. In the present research, we discuss the recent techniques for employed for extraction, and quantitative determination of such compounds in pharmaceutical, and biological specimens. In the frame of this information, this review aims to provide basic principles of chromatography, spectroscopy, and electroanalytical methods for the analysis of anticancer drugs published in the last three years. The review also describes the recent developments regarding enhancing the limit of detection (LOD), the linear dynamic range, and so forth. The results show that the LOD for the chromatographic techniques with the UV detector was obtained equaled over the range 2.0 ng mL^-1-0.2 μg mL^-1, whereas the LOD values for analysis by chromatographic technique with the mass spectrometry (MS) detector was found between 10.0 pg mL^-1-0.002 μg mL^-1. The biological fluids could be directly injected to capillary electrophoresis (CE) in cases where the medicine concentration is at the contents greater than mg L^-1 or g L^-1. Additionally, electrochemical detection of the anticancer drugs has been mainly conducted by the voltammetry techniques with diverse modified electrodes, and lower LODs were estimated between 3.0 ng mL^-1-0.3 μg mL^-1. It is safe to say that the analyses of anticancer drugs can be achieved by employing a plethora of techniques such as electroanalytical, spectroscopy, and chromatography techniques.

Effect of surface properties on the electrochemical response of cynarin by electro-synthesized functionalized-polybithiophene/MWCNT/GNP

Cynarin is one of the biologically active functional components present a wide range of pharmacological applications. Herein, we reported the fabrication and surface properties investigation of a new highly sensitive electrochemical sensor for the detection of cynarin. The electrochemical sensors were fabricated in several steps; the first being the synthesis of bi-thiophene derivatives-based monomers 3,3'-bithiophen (M1); 2-methoxy-5-carbaldehyde-[3,3'-bithiophene] (M2) and 2-((2-methoxy-[3,3'-bithiophen]-5-yl)methylene)malononitrile) (M3) followed by electrochemical polymerization on a glassy carbon electrode after which multi-walled carbon nanotube (MWCNT) and gold nanoparticles (GNP's) were electrodeposited layer-by-layer on the polymer coating to obtain multilayer electrochemical sensors. The morphological properties of the formed polymers were evaluated using SEM analysis and the apparent contact angles to preview the changes in surface properties after the functionalization of monomers and therefore their effects on the detection of cynarin. Analytical parameters such as the accumulation time and pH of the PBS solution which influence the sensitivity of the electrochemical sensors were optimized. Under the optimal conditions the GCE/P3/MWCNT/GNP's showed a wide range of analyte concentrations (1 to 100 μM and 0.01 to 1 μM) and detection limit of 0.0095 using pulse differential voltammetry. In addition, the electrochemical sensors showed good reproducibility, stability and selectivity and they were used successfully for the determination of cynarin in real solutions.