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

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.

An optical sensing platform for the detection of anti-cancer drugs and their cytotoxicity screening using a highly selective phosphorene-based composite

Monitoring therapeutic drugs and their elimination is crucial because they may cause severe side effects on the human body. Methotrexate (MTX) is a widely used anti-cancer drug, which is highly expensive, and the detection of unwanted overdoses of MTX using traditional procedures is time-consuming and involves complex instrumentation. In this work, we have developed a nanocomposite material using phosphorene, cystine, and gold (Ph-Cys-Au) that shows excellent optical properties. This nanocomposite can be used as an optical sensing platform for the detection of MTX in the range 0-260 μM. The synthesized sensing platform is very sensitive, selective, and cost-effective for the detection of MTX. Ph-Cys-Au can effectively detect MTX in aqueous media with a limit of detection (LOD) of about 0.0266 nM (for a linear range of 0-140 μM) and 0.0077 nM (for a linear range of 160-260 μM). The nanocomposite is equally selective for real samples, such as human blood serum (HBS) and artificial urine (AU) with a LOD of 0.0914 nM and 0.0734 nM, respectively. We have also determined the limit of quantification (LOQ); the LOQ values for the aqueous media were 0.0807 nM (for a linear range of 0-140 μM) and 0.0234 nM (for a linear range of 160-260 μM), whereas, the values for HBS and AU were around 0.2771 nM and 0.2226 nM, respectively. Moreover, the nanocomposite also provides a feasible platform for cytotoxicity screening in cancerous cells (Caco-2 cell lines) and non-cancerous cells (L-929 cell lines).

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.

Preparation of Polyvinyl Imine Modified Carbon Quantum Dots and Their Application in Methotrexate Detection

Objective: A sensitive and selective fluorescence-detection platform based on carbon quantum dots (CQDs) was designed and developed for the determination of methotrexate (MTX), for the purpose of minimizing the possible toxic threat of MTX in clinics. Methods: The approach was prepared for the first time by a simple, hydrothermal method, making the synthesis and modification processes realized in one step using polyethyleneimine (PEI), and the proposed PEI-CQDs were obtained with high fluorescence quantum yield (38%). Results: MTX was found highly responsive and effective in quenching the fluorescence of the PEI-CQDs, due to a suggested fluorescence resonance energy transfer mechanism or inner-filter effect. The linear range of MTX was between 1 and 600 μmol/L under optimum conditions, with a detection limit (LOD) as low as 0.33 μmol/L. Furthermore, the fluorescent method was established for the MTX assay, and satisfactory results were acquired in real-sample determination. The average labeled quantity was 98.2%, and the average added standard recovery was 100.9%. Conclusions: The proposed PEI-CQDs showed a remarkable potential for broad applications in biological molecule determination and environmental analysis.

One-Step Preparation of S, N Co-Doped Carbon Quantum Dots for the Highly Sensitive and Simple Detection of Methotrexate

(1) Background: Carbon quantum dots (CQDs) are a new class of carbon nanomaterials with favorable features, such as tunable luminescence, unique optical properties, water solubility, and lack of cytotoxicity; they are readily applied in biomedicine. (2) Methods: S, N co-doped CQDs were prepared to develop a highly selective and sensitive fluorescence technique for the detection of methotrexate (MTX). For this purpose, citric acid and thiourea were used as C, N, and S sources in a single-step hydrothermal process to prepare the S, N co-doped CQDs, which displayed remarkable fluorescence properties. (3) Results: Two optimal emissions were observed at the excitation/emission wavelengths of 320/425 nm, respectively. The two emissions were significantly quenched in the presence of MTX. Under optimal conditions, MTX was detected in the linear concentration range of 1–300 μmol/L, with the detection limit of 0.33 μmol/L. The sensing mechanism was due to the fact that the effect of the inner filter on MTX and S, N-CQDs causes fluorescence quenching. The contents of MTX in real medicine samples were evaluated with acceptable recoveries of 98–101%. (4) Conclusions: This approach has great potential for detecting MTX in pharmaceutical analysis.

An ultrasensitive electrochemical aptasensor based on a single-stranded aptamer-Au@Fe-MIL-88 complex using methylene blue as an electrochemical probe for insulin detection

This work introduces an electrochemical aptasensor based on a single-stranded aptamer-Au@Fe-MIL-88 complex for sensitive and selective determination of insulin using differential pulls voltammetry. Au@Fe-MIL-88 with a large surface area was synthesized and employed as a suitable substrate for immobilization of the aptamer (APT-Au@Fe-MIL-88). Methylene blue (MB), as an electrochemical probe, was intercalated into the aptamer. Graphene oxide (GO) and zinc sulfide (ZnS) were placed on the Au electrode to amplify the MB current. Also, ZnS improves the immobilization of APT-Au@Fe-MIL-88 into the aptasensor through the strong interaction of Au-S. In the presence of the insulin, MB is released from the aptamer due to DNA conformational change, and as a result, the peak intensity of the intercalated MB was decreased. Under optimal conditions, the change in the current of MB was proportional to the insulin concentration in the range of 5.0 × 10^-16-5.0 × 10^-11 mol L^-1, with a superior ultra-low detection limit of 1.3 × 10^-16 mol L^-1. It was observed that the aptasensor is suitable for determining insulin in serum samples with good sensitivity and reproducibility and with recoveries ranging from 96.4 to 102.0%. The relative standard deviations (RSD) were lower than 3.8% (n = 3).

Electrospun Nanofibers for Sensing and Biosensing Applications-A Review

Sensors and biosensors have found applications in many areas, e.g., in medicine and clinical diagnostics, or in environmental monitoring. To expand this field, nanotechnology has been employed in the construction of sensing platforms. Because of their properties, such as high surface area to volume ratio, nanofibers (NFs) have been studied and used to develop sensors with higher loading capacity, better sensitivity, and faster response time. They also allow to miniaturize designed platforms. One of the most commonly used techniques of the fabrication of NFs is electrospinning. Electrospun NFs can be used in different types of sensors and biosensors. This review presents recent studies concerning electrospun nanofiber-based electrochemical and optical sensing platforms for the detection of various medically and environmentally relevant compounds, including glucose, drugs, microorganisms, and toxic metal ions.

Application of Electrospun Nanofibers for Fabrication of Versatile and Highly Efficient Electrochemical Devices: A Review

Electrochemical devices convert chemical reactions into electrical energy or, vice versa, electricity into a chemical reaction. While batteries, fuel cells, supercapacitors, solar cells, and sensors belong to the galvanic cells based on the first reaction, electrolytic cells are based on the reversed process and used to decompose chemical compounds by electrolysis. Especially fuel cells, using an electrochemical reaction of hydrogen with an oxidizing agent to produce electricity, and electrolytic cells, e.g., used to split water into hydrogen and oxygen, are of high interest in the ongoing search for production and storage of renewable energies. This review sheds light on recent developments in the area of electrospun electrochemical devices, new materials, techniques, and applications. Starting with a brief introduction into electrospinning, recent research dealing with electrolytic cells, batteries, fuel cells, supercapacitors, electrochemical solar cells, and electrochemical sensors is presented. The paper concentrates on the advantages of electrospun nanofiber mats for these applications which are mostly based on their high specific surface area and the possibility to tailor morphology and material properties during the spinning and post-treatment processes. It is shown that several research areas dealing with electrospun parts of electrochemical devices have already reached a broad state-of-the-art, while other research areas have large space for future investigations.