Highly sensitive electrochemical determination of methotrexate based on a N-doped hollow nanocarbon sphere modified electrode

Electrochemistry as a Powerful Tool for Investigations of Antineoplastic Agents: A Comprehensive Review

Cancer is most frequently treated with antineoplastic agents (ANAs) that are hazardous to patients undergoing chemotherapy and the healthcare workers who handle ANAs in the course of their duties. All aspects related to hazardous oncological drugs illustrate that the monitoring of ANAs is essential to minimize the risks associated with these drugs. Among all analytical techniques used to test ANAs, electrochemistry holds an important position. This review, for the first time, comprehensively describes the progress done in electrochemistry of ANAs by means of a variety of bare or modified (bio)sensors over the last four decades (in the period of 1982-2021). Attention is paid not only to the development of electrochemical sensing protocols of ANAs in various biological, environmental, and pharmaceutical matrices but also to achievements of electrochemical techniques in the examination of the interactions of ANAs with deoxyribonucleic acid (DNA), carcinogenic cells, biomimetic membranes, peptides, and enzymes. Other aspects, including the enantiopurity studies, differentiation between single-stranded and double-stranded DNA without using any label or tag, studies on ANAs degradation, and their pharmacokinetics, by means of electrochemical techniques are also commented. Finally, concluding remarks that underline the existence of a significant niche for the basic electrochemical research that should be filled in the future are presented.

Simple and sensitive electrochemical sensing of amethopterin by using carbon nanobowl/cyclodextrin electrode

Resulted from the severe side effects, the development of inexpensive, simple and sensitive method for amethopterin (ATP, an antineoplastic drug) is very important but it still remains a challenge. In this work, low cost nanohybrid composed of carbon nanobowl (CNB) and β-cyclodextrins (β-CD) (CNB-CD) was prepared with a simple autopolymerization way and applied as electrode material to develop a novel electrochemical sensor of ATP. Scanning-/transmission-electron microscopy, Fourier transform infrared spectrum, photographic image and electrochemical technologies were utilized to characterize morphologies and structure of the as-prepared CNB and CNB-CD materials. On the basic of the coordination advantages from CNB (prominent electrical property and surface area) and β-CD (superior molecule-recognition and solubility capabilities), the CNB-CD nanohybrid modified electrode exhibits superior sensing performances toward ATP, and a low detection limit of 0.002 μM coupled with larger linearity of 0.005-12.0 μM are obtained. In addition, the as-prepared sensor offers desirable repeatability, stability, selectivity and practical application property, confirming that this proposal may have important applications in the determination of ATP.

Aptamer/proximity hybridization-based label-free and highly sensitive colorimetric detection of methotrexate via polymerization/nicking recycling amplifications

Methotrexate (MTX) is one of the commonly used therapeutic drugs for treating various tumors and autoimmune diseases. However, high dose usage of MTX may cause severe side effects and the monitoring of MTX is therefore critical. By coupling a new MTX aptamer-based proximity hybridization with polymerization/nicking reaction (PNR) recycling amplifications, we develop here a sensitive and label-free colorimetric approach for MTX detection in diluted human serums. The MTX molecules can bind and switch the conformation of aptamers in the DNA duplex probes to initiate subsequent proximity hybridization-induced PNR recycling processes for the yield of a great deal of G-quadruplexes with the assistance of two single-stranded assistant DNA sequences. Hemin subsequently combines with these G-quadruplexes to produce lots of G-quadruplex/hemin horseradish peroxidase (HRP) mimicking DNAzymes, which then catalyze intensified color transition of the substrate solution to exhibit highly magnified UV-Vis absorption for label-free and ultrasensitive detection of MTX at concentration as low as 5.66 nM in the range of 10 nM to 1 μM. High selectivity of the developed method also enables it to monitor low levels of MTX in diluted serum samples, which offers such a method enormous potentials for convenient and highly sensitive detection of other small molecule drugs for various clinical applications.

Engineered tenorite structure of barium-enriched copper oxide for on-site monitoring of cytotoxic methotrexate in environmental samples

Emerging pharmaceutical pollutants pose a threat to both human and environmental health. The removal and monitoring of such pollutants necessitate the use of practical on-site monitoring devices; however, the designs of such devices are underdeveloped. This study involves the fabrication of a low-cost sensor based on barium-incorporated copper oxide (Ba-CuO) for the on-site monitoring of the cytotoxic drug methotrexate (MTRX) in water and sediment samples. The tenorite structure of CuO was slightly enriched with Ba ions at the td sites, distorting the tetrahedron and enhancing its electrochemical properties. Ba-CuO was obtained from Cu(NO₃)₂ and Ba(OH)₂ by a ligand exchange protocol and was characterized using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. In addition, the Ba-CuO sensor was tested under various conditions, and it could detect MTRX at concentrations as low as 0.4 nM, with a high sensitivity of 1.3567 µA µM^-1 cm^-2. On-site monitoring yielded recoveries of greater than 93 % from spiked samples, thus exhibiting excellent reproducibility and stability. Therefore, the developed method is practical and has no matrix effect on the MTRX sensor.

In-situ formation of niobium oxide – niobium carbide – reduced graphene oxide ternary nanocomposite as an electrochemical sensor for sensitive detection of anticancer drug methotrexate

Engineering the nanostructure of an electrocatalyst is crucial in developing a high-performance electrochemical sensor. This work exhibits the hydrothermal followed by annealing synthesis of niobium oxide/niobium carbide/reduced graphene oxide (NbO/NbC/rGO) ternary nanocomposite. The oval-shaped NbO/NbC nanoparticles cover the surface of rGO evenly, and the rGO nanosheets are interlinked to produce a micro-flower-like architecture. The NbO/NbC/rGO nanocomposite-modified electrode is presented here for the first time for the rapid and sensitive electrochemical detection of the anticancer drug methotrexate (MTX). Down-sized NbO/NbC nanoparticles and rGO's high surface area provide many active sites with a rapid electron transfer rate, making them ideal for MTX detection. In comparison to previously reported MTX sensors, the developed drug sensor exhibits a lower oxidation potential and a higher peak current responsiveness. The constructed sensors worked analytically well under optimal conditions, as shown by a low detection limit of 1.6 nM, a broad linear range of 0.1-850 µM, and significant recovery findings (∼98 %, (n = 3)) in real samples analysis. Thus, NbO/NbC/rGO nanocomposite material for high-performance electrochemical applications seems promising.

Simultaneous and selective electrochemical sensing of methotrexate and folic acid in biological fluids and pharmaceutical samples using Fe3O4/ppy/Pd nanocomposite modified screen printed graphite electrode

The purpose of this study was to fabricate an electrochemical sensor for the detection of methotrexate and folic acid based on a screen-printed graphite electrode (SPGE) modified with prepared iron oxide (Fe₃O₄)/polypyrrole (ppy)/Palladium (Pd) nanocomposite. Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR) techniques were employed to characterize the Fe₃O₄/ppy/Pd nanocomposite. The produced modifier was used to induce a remarkable electrocatalytic impact relative to the oxidation of methotrexate, which caused the potential peak shift to a less positive amount (from 800 mV to about 500 mV) and improved the peak current (from 5.3 μA to about 16 μA). Methotrexate peak current was linearly dependent on its concentration from 0.03100.0 μM and the limit of detection (LOD) was estimated at 7.0 nM. The methotrexate and folic acid were co-detected by the proposed sensor. The experimental results indicated that the oxidation peaks of methotrexate and folic acid were separated about 200 mV in phosphate buffer solution (PBS) at pH 7.0. Fe₃O₄/ppy/Pd/SPGE was successfully able to detect methotrexate and folic acid in pharmaceutical and biological samples with excellent recovery.

Simple, low-cost and sensitive electrochemical sensing of antineoplastic drug amethopterin based on a nanocarbon black modified electrode

Various methods have been proposed currently to detect amethopterin (ATP, a widely used anticancer drug that is also called methotrexate); however, a simple and low-cost electrochemical method coupled with high sensitivity is scarce. In this study, by using low-cost and readily available nanocarbon black (NCB), which has excellent conductivity and stable dispersion in water as well as large surface area, as electrode materials to modify a glassy carbon electrode (GCE), a simple, inexpensive and highly-sensitive electrochemical sensor was constructed based on NCB/GCE. The electrochemical behaviors of ATP at both NCB/GCE and GCE were studied; the results show that the peak current of ATP at NCB/GCE is extremely higher than that at the bare GCE. For sensing ATP with high sensitivity, various control conditions including accumulation time, pH values of the phosphate buffer solution and NCB amount were optimized. The quantitative testing results show that NCB/GCE presents excellent sensing performances with a wide linearity range from 0.01 to 10.0 μM and low limit of detection (4.0 nM) towards ATP. Moreover, the investigation in the reproducibility and stability as well as selectivity of NCB/GCE demonstrated that the related results are also satisfactory. It is thus simple and effective method for ATP analysis and has important applications.