Differential pulse adsorptive stripping voltammetric determination of methotrexate using a functionalized carbon nanotubes-modified glassy carbon electrode

Determination of methotrexate in plasma and environmental samples using an electrochemical sensor modified by UiO66-NH2/mesoporous carbon nitride composite and synergistic signal amplification with decorated AuNPs

Electrochemical methods have low toxicity, fast response and, easy operation. By modifying electrochemical sensors with a conductive and porous modifier, their sensitivity and selectivity can be improved. Nanomaterials with new and extraordinary properties are a new approach in science and especially in electrochemical sensors. In this study, UiO66-NH2/mesoporous carbon nitride (M - C3N4) composite provides a porous structure for decorated Au nanoparticles (AuNPs) to prepare a potent modifier for carbon paste electrode (CPE). Due to environmental toxicity of methotrexate, its sensitive, fast and, low-cost determination in workplace environments is of great interest. So, the modified CPE was applied as a sensitivity analysis approach for methotrexate in plasma samples. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as techniques to optimize the analysis and measurement of methotrexate. To measure this drug, several effective parameters were optimized and a calibration curve was drawn under optimal conditions. The calibration curve showed a linear range from 0.5 to 150 μM with a detection limit of 0.15 μM for methotrexate. Examining the repeatability of the response of one electrode and multiple electrodes under optimal conditions shows the high precision of the developed method. Finally, this developed method based on UiO66-NH2/M-gC3N4/AuNPs|CPE was used to determine the methotrexate in the plasma sample using the standard addition method.

Novel and Highly Sensitive Electrochemical Sensor for the Determination of Oxytetracycline Based on Fluorine-Doped Activated Carbon and Hydrophobic Deep Eutectic Solvents

Residues of oxytetracycline (OTC), a veterinary antibiotic and growth promoter, can be present in animal-derived foods; their consumption is harmful to human health and their presence must therefore be detected and regulated. However, the maximum residue limit is low, and consequently highly sensitive and accurate detectors are required to detect the residues. In this study, a novel highly sensitive electrochemical sensor for the detection of OTC was developed using a screen-printed electrode modified with fluorine-doped activated carbon (F-AC/SPE) combined with a novel deep eutectic solvent (DES). The modification of activated carbon by doping with fluorine atoms (F-AC) enhanced the adsorption and electrical activity of the activated carbon. The novel hydrophobic DES was prepared from tetrabutylammonium bromide (TBABr) and a fatty acid (malonic acid) using a green synthesis method. The addition of the DES increased the electrochemical response of F-AC for OTC detection; furthermore, it induced preconcentration of OTC, which increased its detectability. The electrostatic interactions between DES and OTC as well as the adsorption of OTC on the surface of the modified electrode through H-bonding and π-π interactions helped in OTC detection, which was quantified based on the decrease in the anodic peak potential (E _pa = 0.3 V) of AC. The electrochemical behavior of the modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of OTC exhibited a linear response in the range 5-1500 μg L^-1, with a detection limit of 1.74 μg L^-1. The fabricated electrochemical sensor was successfully applied to determine the OTC in shrimp pond and shrimp samples with recoveries of 83.8-100.5% and 93.3-104.5%, respectively. In addition to the high sensitivity of OTC detection, the proposed electrochemical sensor is simple, cost-effective, and environmentally friendly.

A novel three-dimensional network of CuCr2O4/CuO nanofibers for voltammetric determination of anticancer drug methotrexate

Considering the importance of measuring anticancer drugs, a carbon paste electrode (CPE) modified with CuCr₂O₄/CuO nanofibers in the presence of hydrophobic ionic liquid (IL) was fabricated for methotrexate (MTX) sensing. CuCr₂O₄/CuO nanofibers were prepared by electrospinning method. Then, the morphology and structure of the nanofibers were studied by scanning electron microscopy, thermal analysis, X-ray diffraction, energy-dispersive X-ray, map analysis, and FT-IR spectroscopy. The electrochemical behavior of MTX at CuCr₂O₄/CuO/IL/CPE surface was studied using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. After optimization of the experimental parameters, the prepared sensor showed a low detection limit of 25 nM MTX, based on signal-to-noise (S/N = 3), and it can determine in a wide range of 0.1-300 μM in Britton-Robinson buffer solution at pH 2.5. The modified electrode was used to determine MTX concentration in blood and urine samples with good recoveries of 94.1-104.3. This sensor has several advantages such as low cost, easy preparation, high-performance speed and high sensitivity, selectivity, stability, and repeatability. Graphical abstract Scheme of preparation of CuCr₂O₄/CuO nanofibers by electrospinning method and design of a carbon past electrode using prepared nanofibers (CuCr₂O₄/CuO/IL/CPE). This electrode was used for methotrexate determination in plasma and urine samples using differential pulse voltammetry.

Ultrasound-induced radicals initiated the formation of inorganic-organic Pr2O3/polystyrene hybrid composite for electro-oxidative determination of chemotherapeutic drug methotrexate

To dates, the facile synthesis of inorganic-coated organic polymer composite has received greater attention in the order of research fields including advanced materials and electrochemical analysis owing to the complementary or synergistic effects. In this context, Pr₂O₃ and Pr₂O₃ coated polystyrene (Pr₂O₃/PS) inorganic-organic colloidal composite were prepared via ultrasound-induced radicals initiated precipitation and dispersion polymerization methods. The synthesized Pr₂O₃/PS composite was systematically studied by FE-SEM, TEM, EDX, FT-IR, XRD, and XPS analysis. This composite modified glassy carbon electrode (Pr₂O₃/PS GCE) was utilized to construct a novel electrochemical sensor for the detection assay of chemotherapy agent methotrexate (MTA). Under optimal condition, the designed sensor showed outstanding performance for MTA trace level detection over the linear concentration range of 0.01-236 µM with a detection limit of 0.8 nM for MTA. Furthermore, the prepared sensor accomplished excellent stability and relevant reproducibility, in addition to reliable practical assay in real human blood serum and urine samples. Besides, the possible MTA sensing mechanism of Pr₂O₃/PS GCE has been deliberated in detail. Our finding suggested that the developed Pr₂O₃/PS composite might be a favorable material for the fabrication of the high-performance electrochemical sensor.

Determination of methotrexate in spiked human blood serum using multi-frequency electrochemical immittance spectroscopy and multivariate data analysis

This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55. The data were analysed using multivariate data analysis and showed a concentration dependence and time dependence that could be separated. This allowed the calculation of a multivariate calibration model. The model showed good linear behavior on a logarithmic scale offering a detection limit of 5 × 10^-12 mol L^-1.

Nanostructured materials in electroanalysis of pharmaceuticals

Basic strategies and recent developments for the enhancement of the sensory performance of nanostructures in the electroanalysis of pharmaceuticals are reviewed. A discussion of the properties of nanostructures and their application as modified electrodes for drug assays is presented. The electrocatalytic effect of nanostructured materials and their application in determining low levels of drugs in pharmaceutical forms and biofluids are discussed.

Controlled release of drugs from cellulose acetate matrices produced from sugarcane bagasse: monitoring by square-wave voltammetry

In this paper, cellulose triacetate (CTA) was produced from sugarcane bagasse and used as matrices for controlled release of paracetamol. Symmetric and asymmetric membranes were obtained by formulations of CTA/dichloromethane/drug and CTA/dichloromethane/water/drug, respectively, and they were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Different morphologies of membranes were observed by SEM, and the incorporation of paracetamol was confirmed by lowering of the glass transition temperature (Tg) in the DSC curves. This indicates the existence of interactions between the matrix and the drug. The evaluation of drug release was based on the electrochemical monitoring of paracetamol through its oxidation at a glassy carbon electrode surface using square-wave voltammetry (SWV), which provides fast, precise and accurate in situ measurements. The studies showed a content release of 27% and 45% by the symmetric and asymmetric membranes, respectively, during 8 h.