Electrochemical Affinity Biosensors Based on Selected Nanostructures for Food and Environmental Monitoring

Recent research progress of selenotungstate-based biomolecular sensing materials

Polyoxometalates (POMs) have drawn significant attention on account of their structural designability, compositional diversity and great potential applications. As an indispensable branch of POMs, selenotungstates (SeTs) have been synthesized extensively. Some SeTs have been applied as sensing materials for detecting biomarkers (e.g., metabolites, hormones, cancer markers). To gain a comprehensive understanding of advancements in SeT-based sensing materials, we present an overview that encapsulates the sensing performances and mechanisms of SeT-based biosensors. SeT-based biosensors are categorized into electrochemical catalytic biosensors, electrochemical affinity biosensors, "turn-off" fluorescence biosensors and "turn-on" fluorescence biosensors. We anticipate the expansive potential of SeT-based biosensors in wearable and implantable sensing technologies, which promises to catalyze significant breakthroughs in SeT-based biosensors.

Machine learning-guided the fabrication of nanozyme based on highly-stable violet phosphorene decorated with phosphorus-doped hierarchically porous carbon microsphere for portable intelligent sensing of mycophenolic acid in silage

Violet phosphorene (VP) have been proved to be more stable than black phosphorene, but few reports for its application in electrochemical sensors. In this study, a highly-stable VP decorated with phosphorus-doped hierarchically porous carbon microsphere (PCM) with multiple enzyme-like activities as a nanozyme sensing platform for portable intelligent analysis of mycophenolic acid (MPA) in silage with machine learning (ML) assistance is successfully fabricated. The pore size distribution on the PCM surface is discussed using N2 adsorption tests, and morphological characterization indicates that the PCM is embedded in the layers of lamellar VP. The affinity of the VP-PCM nanozyme obtained under the guidance of the ML model reaches Km = 12.4 μmol/L for MPA. The VP-PCM/SPCE for the efficient detection of MPA exhibits high sensitivity, a wide detection range of 2.49 μmol/L - 71.14 μmol/L with a low limit of detection of 18.7 nmol/L. The proposed ML model with high prediction accuracy (R2 = 0.9999, MAPEP = 0.0081) assists the nanozyme sensor for intelligent and rapid quantification of MPA residues in corn silage and wheat silage with satisfactory recoveries of 93.33%-102.33%. The excellent biomimetic sensing properties of the VP-PCM nanozyme are driving the development of a novel MPA analysis strategy assisted by ML in the context of production requirements of livestock safety.

Anti-Fouling Strategies of Electrochemical Sensors for Tumor Markers

The early detection and prognosis of cancers require sensitive and accurate detection methods; with developments in medicine, electrochemical biosensors have been developed that can meet these clinical needs. However, the composition of biological samples represented by serum is complex; when substances undergo non-specific adsorption to an electrode and cause fouling, the sensitivity and accuracy of the electrochemical sensor are affected. In order to reduce the effects of fouling on electrochemical sensors, a variety of anti-fouling materials and methods have been developed, and enormous progress has been made over the past few decades. Herein, the recent advances in anti-fouling materials and strategies for using electrochemical sensors for tumor markers are reviewed; we focus on new anti-fouling methods that separate the immunorecognition and signal readout platforms.

Antibody-Conjugated Electrospun Nanofibers for Electrochemical Detection of Methamphetamine

Multifunctional electrospun nanofibers (ENs) with improved properties have increased attention nowadays. Their insoluble forms in water with decreased hydrophobicity are desired for the immobilization of biological molecules. Also, the addition of functional groups on the backbone provides the conjugation of biomolecules onto the surface of ENs via covalent bonds to increase their stability. Here, poly(vinylidene fluoride) (PVDF) was chosen to prepare a platform, which is insoluble in water, and polyethylenimine (PEI) was used to add amine groups on the surface of ENs to bind biological molecules via covalent conjugation. So, PVDF-PEI nanofibers were prepared on a glassy carbon electrode to immobilize an antimethamphetamine antibody (Anti-METH) as a model biomolecule. The obtained PVDF-PEI/Anti-METH was used for the bioelectrochemical detection of methamphetamine (METH), a common illicit drug. Bioelectrochemical detection of METH on PVDF-PEI/Anti-METH-coated electrodes was carried out by voltammetry in the range of 2.0-50 ng/mL METH. Moreover, the effect of dansyl chloride (DNC) derivatization of METH on the sensitivity of PVDF-PEI/Anti-METH was tested. Finally, METH analysis was carried out in synthetic body fluids. The obtained results showed that PVDF-PEI ENs can be adopted as an immobilization matrix for the biorecognition elements of biobased detection systems, and the derivative of METH (METH-DNC) increased the sensitivity of PVDF-PEI/Anti-METH.

Nanozymes towards Personalized Diagnostics: A Recent Progress in Biosensing

This review highlights the recent advancements in the field of nanozymes and their applications in the development of point-of-care biosensors. The use of nanozymes as enzyme-mimicking components in biosensing systems has led to improved performance and miniaturization of these sensors. The unique properties of nanozymes, such as high stability, robustness, and surface tunability, make them an attractive alternative to traditional enzymes in biosensing applications. Researchers have explored a wide range of nanomaterials, including metals, metal oxides, and metal-organic frameworks, for the development of nanozyme-based biosensors. Different sensing strategies, such as colorimetric, fluorescent, electrochemical and SERS, have been implemented using nanozymes as signal-producing components. Despite the numerous advantages, there are also challenges associated with nanozyme-based biosensors, including stability and specificity, which need to be addressed for their wider applications. The future of nanozyme-based biosensors looks promising, with the potential to bring a paradigm shift in biomolecular sensing. The development of highly specific, multi-enzyme mimicking nanozymes could lead to the creation of highly sensitive and low-biofouling biosensors. Integration of nanozymes into point-of-care diagnostics promises to revolutionize healthcare by improving patient outcomes and reducing costs while enhancing the accuracy and sensitivity of diagnostic tools.

Affinity-based electrochemical sensors for biomolecular detection in whole blood

The detection and/or quantification of biomarkers in blood is important for the early detection, diagnosis, and treatment of a variety of diseases and medical conditions. Among the different types of sensors for detecting molecular biomarkers, such as proteins, nucleic acids, and small-molecule drugs, affinity-based electrochemical sensors offer the advantages of high analytical sensitivity and specificity, fast detection times, simple operation, and portability. However, biomolecular detection in whole blood is challenging due to its highly complex matrix, necessitating sample purification (i.e., centrifugation), which involves the use of bulky, expensive equipment and tedious sample-handling procedures. To address these challenges, various strategies have been employed, such as purifying the blood sample directly on the sensor, employing micro-/nanoparticles to enhance the detection signal, and coating the electrode surface with blocking agents to reduce nonspecific binding, to improve the analytical performance of affinity-based electrochemical sensors without requiring sample pre-processing steps or laboratory equipment. In this article, we present an overview of affinity-based electrochemical sensor technologies that employ these strategies for biomolecular detection in whole blood.

Application of Nanotechnology in COVID-19 Infection: Findings and Limitations

There is an urgent need to address the global mortality of the COVID-19 pandemic, as it reached 6.3 million as of July 2022. As such, the experts recommended the mass diagnosis of SARS-CoV-2 infection at an early stage using nanotechnology-based sensitive diagnostic approaches. The development of nanobiosensors for Point-of-Care (POC) sampling of COVID-19 could ensure mass detection without the need for sophisticated laboratories or expert personnel. The use of Artificial Intelligence (AI) techniques for POC detection was also proposed. In addition, the utilization of various antiviral nanomaterials such as Silver Nanoparticles (AgNPs) for the development of masks for personal protection mitigates viral transmission. Nowadays, nano-assisted vaccines have been approved for emergency use, but their safety and effectiveness in the mutant strain of the SARS-CoV-2 virus remain challenging. Methodology: Updated literature was sourced from various research indexing databases such as PubMed, SCOPUS, Science Direct, Research Gate and Google Scholars. Result: We presented the concept of novel nanotechnology researched discovery, including nano-devices, electrochemical biosensing, nano-assisted vaccine, and nanomedicines, for use in recent times, which could be a formidable step for future management of COVID-19.

Design and implementation of low-cost portable potentiostat based on wechat

The potentiostat is critical in the development of electrochemical systems; however, its cumbersome detection and high cost considerably limit its large-scale application. To provide an affordable alternative to developing countries and resource-constrained areas, this study designs an electrochemical detection system based on smartphones, which uses Bluetooth Low Energy to convert open-source potentiostat data based on PSoC-5LP. The WeChat application on the smartphone provides an interface for entering experimental parameters and visualizing the results in real time. The smartphone-based electro-chemical detection system has a simple design and reduces the size (10?3?0.3 cm) and the cost of the hardware ($ 18). The system performs the most commonly used cyclic voltammetry for electrochemical detection, with results that are comparable to those obtained using a commercial potentiostat and an error rate of 1.3 %. In the classical teaching experiment of electrochemical determination of ascorbic acid in orange juice samples, the measured value of the system is 0.367 ? 0.012 mg/mL, compared with the standard reference value of 0.37 mg/ mL, which is obviously a convincing value. Therefore, this system is a low-cost, reliable alternative to a potentiostat for research, education, or product integration development.

Electrochemical DNA Sensor Based on Acridine Yellow Adsorbed on Glassy Carbon Electrode

Electrochemical DNA sensors offer unique opportunities for the sensitive detection of specific DNA interactions. In this work, a voltametric DNA sensor is proposed on the base of glassy carbon electrode modified with carbon black, adsorbed acridine yellow and DNA for highly sensitive determination of doxorubicin antitumor drug. The signal recorded by cyclic voltammetry was attributed to irreversible oxidation of the dye. Its value was altered by aggregation of the hydrophobic dye molecules on the carbon black particles. DNA molecules promote disaggregation of the dye and increased the signal. This effect was partially suppressed by doxorubicin compensate for the charge of DNA in the intercalation. Sensitivity of the signal toward DNA and doxorubicin was additionally increased by treatment of the layer with dimethylformamide. In optimal conditions, the linear range of doxorubicin concentrations determined was 0.1 pM–1.0 nM, and the detection limit was 0.07 pM. No influence of sulfonamide medicines and plasma electrolytes on the doxorubicin determination was shown. The DNA sensor was tested on two medications (doxorubicin-TEVA and doxorubicin-LANS) and showed recoveries of 102–105%. The DNA sensor developed can find applications in the determination of drug residues in blood and for the pharmacokinetics studies.

Voltammetric Immunosensor to Track a Major Peanut Allergen (Ara h 1) in Food Products Employing Quantum Dot Labels

Tracking unreported allergens in commercial foods can avoid acute allergic reactions. A 2-step electrochemical immunosensor was developed for the analysis of the peanut allergen Ara h 1 in a 1-h assay (<15 min hands-on time). Bare screen-printed carbon electrodes (SPCE) were used as transducers and monoclonal capture and detection antibodies were applied in a sandwich-type immunoassay. The short assay time was achieved by previously combining the target analyte and the detection antibody. Core/shell CdSe@ZnS Quantum Dots were used as electroactive label for the detection of the immunological interaction by differential pulse anodic stripping voltammetry. A linear range between 25 and 1000 ng·mL-1 (LOD = 3.5 ng·mL-1), an adequate precision of the method (Vx0 ≈ 6%), and a sensitivity of 23.0 nA·mL·ng-1·cm-2 were achieved. The immunosensor was able to detect Ara h 1 in a spiked allergen-free product down to 0.05% (m/m) of peanut. Commercial organic farming cookies and cereal and protein bars were tested to track and quantify Ara h 1. The results were validated by comparison with an ELISA kit.

Analytical Parameters of a Novel Glucose Biosensor Based on Grafted PFM as a Covalent Immobilization Technique

Bioanalytical methods, in particular electrochemical biosensors, are increasingly used in different industrial sectors due to their simplicity, low cost, and fast response. However, to be able to reliably use this type of device, it is necessary to undertake in-depth evaluation of their fundamental analytical parameters. In this work, analytical parameters of an amperometric biosensor based on covalent immobilization of glucose oxidase (GOx) were evaluated. GOx was immobilized using plasma-grafted pentafluorophenyl methacrylate (pgPFM) as an anchor onto a tailored HEMA-co-EGDA hydrogel that coats a titanium dioxide nanotubes array (TiO2NTAs). Finally, chitosan was used to protect the enzyme molecules. The biosensor offered outstanding analytical parameters: repeatability (RSD = 1.7%), reproducibility (RSD = 1.3%), accuracy (deviation = 4.8%), and robustness (RSD = 2.4%). In addition, the Ti/TiO2NTAs/ppHEMA-co-EGDA/pgPFM/GOx/Chitosan biosensor showed good long-term stability; after 20 days, it retained 89% of its initial sensitivity. Finally, glucose concentrations of different food samples were measured and compared using an official standard method (HPLC). Deviation was lower than 10% in all measured samples. Therefore, the developed biosensor can be considered to be a reliable analytical tool for quantification measurements.

Smartphone-Based NFC Potentiostat for Wireless Electrochemical Sensing

Most electrochemical sensing requires affordable, portable and easy-to-use electrochemical devices for use in point-of-care testing and resource-limited settings. This work presents the design and evaluates the analytical performance of a near-field communication (NFC) potentiostat, a flat card-sized electrochemical device containing a microchip for electrical analysis and an NFC antenna for smartphone connection. The NFC interface is a wireless connection between the microchip and smartphone to simplify measuring units and make the potentiostat into a passive operated device, running without a battery. The proposed potentiostat can perform the common electrochemical techniques including cyclic voltammetry and chronoamperometry with a current range and voltage range of ±20 µA and ±0.8 V. The performance of the NFC potentiostat is compared to a commercial benchtop potentiostat using ferricyanide as a standard solution. The results show that the NFC potentiostat is comparable to a commercial benchtop potentiostat for both cyclic voltammetry and chronoamperometry measurements. The application of the proposed potentiostat is demonstrated by measuring ascorbic acid concentration. As described, the NFC potentiostat, which is compatible with a smartphone, is low-cost, small in size and user-friendly. Thus, the device can be developed for on-site measurement to apply in various fields.