Application of electrochemical sensors based on nanomaterials modifiers in the determination of antipsychotics

At present, the content of antipsychotics in samples is always analyzed by traditional detection methods, including mass spectrometry (MS), spectrophotometry, fluorescence, capillary electrophoresis (CE). However, conventional methods are cumbersome and complex, require a large sample volume, many pre-processing steps, long analysis cycles, expensive instruments, and need well-trained detection capabilities personnel. In addition, patients with schizophrenia require frequent and painful blood collection procedures, which adds additional treatment costs and time burdens. In view of these factors, electrochemical methods have become the most promising candidate technology for timely analysis due to their low cost, simple operation, excellent sensitivity and specificity. As we all know, nanomaterials play an extremely important role in electrochemical sensing applications. As the sensor modifiers, nanomaterials enable electrochemical analysis to overcome the time-consuming and labor-intensive shortcomings of traditional detection methods, and greatly reduce the research cost. Nanomaterials modified electrodes can be used as sensors to determine the concentration of antipsychotics in organisms quickly and accurately, which is a bright spot in the application of nanomaterials. The combination of different nanomaterials can even form a nanocomposite with a synergistic effect. This paper firstly reviews the application of nanomaterials-modified sensors on the basis of research in the past ten years, reviews the use of nanomaterial-modified sensors to quickly and accurately determine the concentration of antipsychotics in biological samples, and demonstrates a new idea of using nanomaterials sensors for drug monitoring and determination. At the end of this review, a brief overview is given of the limitations and the future prospects of nanomaterial sensors for the determination of antipsychotics concentrations.

Comparison of Hydrogen Peroxide Secretion From Living Cells Cultured in Different Formats Using Hydrogel-Based LSPR Substrates

Reactive oxygen species (ROS), a number of reactive molecules and free radicals derived from molecular oxygen, are generated as by-products during mitochondrial electron transport within cells. Physiologically, cells are capable of metabolizing the ROS exploiting specific mechanisms. However, if excessive ROS accumulate inside the cells, it will cause the cells apoptosis or necrosis. Hydrogen peroxide (H₂O₂) is one of the essential ROS often participating in chemical reactions in organisms and regulating homeostasis in the body. Therefore, rapid and sensitive detection of H₂O₂ is a significant task in cell biology research. Furthermore, it has been found that cells cultured in different formats can result in different cellular responses and biological activities. In order to investigate the H₂O₂ secretion from the cells cultured in different formats, a hydrogel-based substrate is exploited to separate relatively large molecular (e.g., proteins) for direct measurement of H₂O₂ secreted from living cells in complete cell culture medium containing serum. The substrate takes advantage of the localized surface plasmon resonance (LSPR) method based on enzyme immunoprecipitation. In addition, the H₂O₂ secreted from the cells cultured in different dimensions (suspension of single cells and three-dimensional cell spheroids) treated with identical drugs is measured and compared. The spheroid samples can be prepared with ample amount using a designed microfluidic device with precise control of size. The results show that the H₂O₂ secretion from the cells are great affected by their culture formats.

Colorimetric Detection of Extracellular Hydrogen Peroxide Using an Integrated Microfluidic Device

It is well known that hydrogen peroxide (H₂O₂) is a signaling molecule essential for vital physiological reactions in mammalian cells, such as cell survival, intercellular communication, and cancer metabolism. However, to fully understand the function of H₂O₂, it is critical to monitor its intracellular and/or extracellular concentrations. Current techniques implemented to address this need require large sample volumes, expensive instrumentation, and long sample preparation and analysis times, inapplicable to inline or online monitoring. In this paper, a new integrated microfluidic device capable of overcoming these limitations is demonstrated for the colorimetric detection of extracellular hydrogen peroxide H₂O₂. The device contains an optical waveguide to determine absorbance changes and micromixers to enable complete mixing of reagents using a passive approach. This novel H₂O₂-sensing device has allowed the detection of H₂O₂ in the range of 0.5-60 μM with a detection limit of 167 ± 5.8 nM and a sensitivity of 13.5 ± 0.1 AU/mM. Proof of concept of the device was demonstrated by quantifying H₂O₂ release from benign prostatic epithelial (BPH-1) cells upon stimulation with phorbol 12-myristate 13-acetate (PMA). Results show that this integrated device can be potentially utilized to continuously monitor cell-released metabolites autonomously without constant human supervision during the process. Furthermore, this can be achieved without interfering with the cell culture conditions, as only a very small volume of conditioned media (less than 0.4 μL), and not the cells, is required.

A nanostructured microfluidic device for plasmon-assisted electrochemical detection of hydrogen peroxide released from cancer cells

Non-invasive liquid biopsies offer hope for a rapid, risk-free, real-time glimpse into cancer diagnostics. Recently, hydrogen peroxide (H₂O₂) was identified as a cancer biomarker due to its continued release from cancer cells compared to normal cells. The precise monitoring and quantification of H₂O₂ are hindered by its low concentration and the limit of detection (LOD) in traditional sensing methods. Plasmon-assisted electrochemical sensors with their high sensitivity and low LOD make a suitable candidate for effective detection of H₂O₂, yet their electrical properties need to be improved. Here, we propose a new nanostructured microfluidic device for ultrasensitive, quantitative detection of H₂O₂ released from cancer cells in a portable fashion. The fluidic device features a series of self-organized gold nanocavities, enhanced with graphene nanosheets having optoelectrical properties, which facilitate the plasmon-assisted electrochemical detection of H₂O₂ released from human cells. Remarkably, the device can successfully measure the released H₂O₂ from breast cancer (MCF-7) and prostate cancer (PC3) cells in human plasma. Briefly, direct amperometric detection of H₂O₂ under simulated visible light illumination showed a superb LOD of 1 pM in a linear range of 1 pM-10 μM. We thoroughly studied the formation of self-organized plasmonic nanocavities on gold electrodes via surface and photo-electrochemical characterization techniques. In addition, the finite-difference time domain (FDTD) simulation of the electric field demonstrates the intensity of charge distribution at the nanocavity structure edges under visible light illumination. The superb LOD of the proposed electrode combining gold plasmonic nanocavities and graphene sheets paves the way for the development of non-invasive plasmon-assisted electrochemical sensors that can effectively detect low concentrations of H₂O₂ released from cancer cells.

Sonochemical synthesis of iron-graphene oxide/honeycomb-like ZnO ternary nanohybrids for sensitive electrochemical detection of antipsychotic drug chlorpromazine

We report a novel electrochemical sensor for the sensitive and selective determination of the antipsychotic drug chlorpromazine (CPZ) based on the iron (Fe) nanoparticles-loaded graphene oxide (GO-Fe)/three dimensional (3D) honeycomb-like zinc oxide (ZnO) nanohybrid modified screen printed carbon electrode (SPCE). The 3D hierarchical honeycomb-like ZnO was synthesized using a novel aqueous hydrothermal method and the GO-Fe/ZnO nanohybrid was prepared based on an inexpensive and fast sonochemical method using a high-intensity ultrasonic bath (Delta DC200H, 200 W, 40 KHz). Characterizations including scanning electron microscopy, elemental mapping, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy were carried out as part of this work. The electrocatalytic oxidation behavior of CPZ at various electrodes was investigated using the cyclic voltammetry technique, through which the GO-Fe/ZnO modified SPCE was identified as the best performing electrode. The quantitative determination of CPZ was then performed using the differential pulse voltammetry technique. The as-prepared GO-Fe/ZnO/SPCE sensor exhibited a quick and sensitive response towards the oxidation of CPZ with linear concentration ranges from 0.02 to 172.74 μM and 222.48 to 1047.74 μM. The modified SPCE sensor displayed a low detection limit (LOD) of 0.02 µM and a high sensitivity of 7.56 µA µM^-1 cm^-2. The proposed sensor also showed remarkable operational and storage stability, reproducibility, and repeatability. Furthermore, the practicability of the GO-Fe/ZnO/SPCE sensor has been verified with real sample analysis using commercial antipsychotic CPZ tablets and human urine samples, and adequate recovery has been achieved.

Fingerprinting Green Curry: An Electrochemical Approach to Food Quality Control

The detection and identification of multiple components in a complex sample such as food in a cost-effective way is an ongoing challenge. The development of on-site and rapid detection methods to ensure food quality and composition is of significant interest to the food industry. Here we report that an electrochemical method can be used with an unmodified glassy carbon electrode for the identification of the key ingredients found within Thai green curries. It was found that green curry presents a fingerprint electrochemical response that contains four distinct peaks when differential pulse voltammetry is performed. The reproducibility of the sensor is excellent as no surface modification is required and therefore storage is not an issue. By employing particle swarm optimization algorithms the identification of ingredients within a green curry could be obtained. In addition, the quality and freshness of the sample could be monitored by detecting a change in the intensity of the peaks in the fingerprint response.