Disposable non-enzymatic electrochemical glucose sensors based on screen-printed graphite macroelectrodes modified via a facile methodology with Ni, Cu, and Ni/Cu hydroxides are shown to accurately determine glucose in real human serum blood samples

Electrochemical nonenzymatic glucose sensors catalyzed by Au nanoclusters on metallic nanotube arrays and polypyrrole nanowires

Monitoring blood glucose level is critical, since its abnormality leads to diabetes and causes death, even though glucose is essential for human living. Herein, the sensing study was performed on electrochemical nonenzymatic glucose sensors, which are composed of an Au nanocluster (AuNC) catalyst deposited on a metallic nanotube array (MeNTA) and polypyrrole nanowire (PPyNW). The AuNC was produced by irradiating a femtosecond pulse laser to the Au precursor solution, and it is a simple and facile method. The successful deposition of AuNC on both MeNTA and PPyNW was confirmed by means of the surface morphology and the Au content increase. On the exploration by cyclic voltammetry in alkaline condition, AuNC/MeNTA electrodes showed better performance than AuNC/PPyNW electrodes: The former was a remarkable electrocatalytic detector towards glucose oxidation with better sensitivity, lower detection limit, wider linear range, and longer-term stability without interference from potential interfering agents such as ascorbic acid, urea, NaCl, KCl, etc. Moreover, nonenzymatic AuNC/MeNTA electrodes exhibited high precision and accuracy in real human blood samples and, thus, can be a promising candidate in glucose sensing applications.

Enzyme-free electrochemical sensor platforms based on transition metal nanostructures for clinical diagnostics

The detection of emergent biomarkers is of key significance in numerous clinical, biological, and biomedical fields. Specifically, the design and development of potent electrochemical lactic acid and glucose sensing platforms are especially in great demand in a variety of industries, including those involved in clinical analysis, biomedicine, biological, food, cosmetics, pharmaceuticals, leather, sports, and chemical industries. Nanostructured transition metal-derived materials have opened the door to electrochemical sensors and biosensors due to their advantages of high surface-to-volume ratio, surface reaction activity, catalytic activity, and strong adsorption capability. The primary aim of the present minireview is to highlight the advancement of enzyme-free electrochemical sensor platforms based on transition metal-derived nanostructures with high electrocatalytic activity and sensing performance towards lactic acid and glucose in practical samples. The preparation approaches, structural and composition monitoring, fabrication of sensing electrodes, catalytic activity, sensing performance in real samples, and the exploration of sensing mechanisms are majorly concentrated on in most of our recent research studies. Moreover, state-of-the-art transition metal-derived nanostructure-derived electrochemical sensor platforms, critical comparison of the analytical performance of the sensor platforms, and the future perspectives of the enzyme-free electrochemical sensor for clinical diagnostics are described.

Fully automated station for testing, characterizing and modifying screen-printed electrodes

Electrochemical detection systems that provide either quantitative or sample-to-answer information are promising for various analytical applications in the emerging field of point-of-care testing (POCT). Nevertheless, in mobile POC systems optical detection is currently more preferred compared to electrochemical detection due to the insufficient robustness of electrochemical detection approaches toward "real world" use. Over the last couple of decades, screen-printed electrodes (SPEs) have emerged as a simple and low-cost electrochemical detection platform. Here, we report, firstly and solely, a novel benchtop system for the processing of electrochemical methods on SPE platforms. Our solution prevents operator errors from occurring while processing and testing SPEs, achieves an automatic processing of more than 300 electrodes per day and enables comparative testing due to the presence of two simultaneous working channels; furthermore, the SPEs used can be stored in specially-designed cartridges. This novel device helps to overcome the major disadvantages in processing SPE technology, such as a low level of automation and issues with process repeatability, making this technology more efficient and enabling faster growth in industry.

Techniques to Improve the Performance of Planar Microwave Sensors: A Review and Recent Developments

Planar microwave sensors have become increasing developed in recent decades, especially in material characterization (solid/liquid) as they provide regions highly sensitive to the surrounding medium. However, when it comes to deciphering the content of practical biological analytes or chemical components inside a host medium, even higher sensitivities are required due to their minute concentrations. This review article presents a comprehensive outlook on various methodologies to enhance sensitivity (e.g., coupling resonators, channel embedding, analyte immobilization, resonator pattern recognition, use of phase variation, using coupled line section, and intermodulation products), resolution (active sensors, differential measurements), and robustness (using machine learning) of arbitrary sensors of interest. Some of the most practical approaches are presented with prototype examples, and the main applications of incorporating such procedures are reported. Sensors with which the proposed techniques are implemented exhibit higher performance for high-end and real-life use.

A dual-channel colorimetric and fluorescent sensor for the rapid and ultrasensitive detection of kanamycin based on gold nanoparticles-copper nanoclusters

In this work, a dual-channel assay was constructed for the colorimetric and fluorescent detection of kanamycin (KAN) based on gold nanoparticles (Au NPs) and copper nanoclusters (Cu NCs). Initially, the fluorescence of Cu NCs was quenched by 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT)-functionalized Au NPs due to the inner filter effect (IFE). The existence of KAN acted as a molecular bridge to interact with AHMT via hydrogen bonds and induced the aggregation of AHMT-Au NPs, leading to a change in the color of the gold colloidal solution from reddish-violet to blue within 2 min. Moreover, the aggregated AHMT-Au NPs can weaken its IFE toward Cu NCs and result in fluorescence restoration. With the sensor employed here, the concentration of KAN can be quantitatively analyzed through double channels, and a low LOD (limit of detection) of 1.9 nM and 1.2 nM was realized by the colorimetric and fluorescent method, respectively. Benefitting from the short response time, high sensitivity, and good reliability, the established assay offered great opportunities for the on-site monitoring of antibiotics in environmental samples.

Electrochemical Characterization of Modified Glassy Carbon Electrodes for Non-Enzymatic Glucose Sensors

The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. Our approach involved comprehensive morphologic and structural characterization of copper sulfides as well as drop-casted suspensions based on three different polymers-cationic chitosan, anionic Nafion, and nonionic polyvinylpyrrolidone (PVP). For this purpose, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were applied. Subsequently, comparative studies of electrochemical properties of bare glassy carbon electrode (GCE), polymer- and copper sulfides/polymer-modified GCEs were performed using electrochemical impedance spectroscopy (EIS) and voltammetry. The results from EIS provided an explanation for the enhanced analytical performance of Cu-PVP/GCE over chitosan- and Nafion-based electrodes. Moreover, it was found that the pH of the electrolyte significantly affects the electrocatalytic behavior of copper sulfides, indicating the importance of OH_ads in the detection mechanism. Additionally, diffusion was denoted as a limiting step in the irreversible electrooxidation process that occurs in the proposed system.