Metabolic pathway-based self-assembled Au@MXene liver microsome electrochemical biosensor for rapid screening of aflatoxin B1

Nanobioelectrocatalysis Using Human Liver Microsomes and Cytochrome P450 Bactosomes: Pyrenyl-Nanocarbon Electrodes

Human liver microsomes containing various drug-metabolizing cytochrome P450 (P450) enzymes, along with their NADPH-reductase bound to phospholipid membranes, were absorbed onto 1-pyrene butylamine pi-pi stacked with amine-functionalized multiwalled carbon nanotube-modified graphite electrodes. The interfaced microsomal biofilm demonstrated direct electrochemical communication with the underlying electrode surface and enhanced oxygen reduction electrocatalytic activity typical of heme enzymes such as P450s over the unmodified electrodes and nonenzymatic currents. Similar enhancements in currents were observed when the bioelectrodes were constructed with recombinant P450 2C9 (single isoform) expressed bactosomes. The designed liver microsomal and 2C9 bactosomal bioelectrodes successfully facilitated the electrocatalytic conversion of diclofenac, a drug candidate, into 4'-hydroxydiclofenac. The enzymatic electrocatalytic metabolite yield was several-fold greater on the modified electrodes than on the unmodified bulk graphite electrodes adsorbed with a microsomal or bactosomal film. The nonenzymatic metabolite production was less than the enzymatically catalyzed metabolite yield in the designed microsomal and bactosomal biofilm electrodes. To test the throughput potential of the designed biofilms, eight-electrode array configurations were tested with the microsomal and bactosomal biofilms toward electrochemical 4'-hydroxydiclofenac metabolite production from diclofenac. The stability of the designed microsomal bioelectrode was assessed using nonfaradaic impedance spectroscopy over 40 h, which indicated good stability.

Recent advances using MXenes in biomedical applications

An MXene is a novel two-dimensional transition metal carbide or nitride, with a typical formula of Mn+1XnTx (M = transition metals, X = carbon or nitrogen, and T = functional groups). MXenes have found wide application in biomedicine and biosensing, owing to their high biocompatibility, abundant reactive surface groups, good conductivity, and photothermal properties. Applications include photo- and electrochemical sensors, energy storage, and electronics. This review will highlight recent applications of MXene and MXene-derived materials in drug delivery, tissue engineering, antimicrobial activity, and biosensors (optical and electrochemical). We further elaborate on recent developments in utilizing MXenes for photothermal cancer therapy, and we explore multimodal treatments, including the integration of chemotherapeutic agents or magnetic nanoparticles for enhanced therapeutic efficacy. The high surface area and reactivity of MXenes provide an interface to respond to the changes in the environment, allowing MXene-based drug carriers to respond to changes in pH, reactive oxygen species (ROS), and electrical signals for controlled release applications. Furthermore, the conductivity of MXene enables it to provide electrical stimulation for cultured cells and endows it with photocatalytic capabilities that can be used in antibiotic applications. Wearable and in situ sensors incorporating MXenes are also included. Major challenges and future development directions of MXenes in biomedical applications are also discussed. The remarkable properties of MXenes will undoubtedly lead to their increasing use in the applications discussed here, as well as many others.

Constructed MXene matrix composites as sensing material and applications thereof: A review

Most studies on MXene matrix composites for sensor development have primarily focused on synthesis and application. Nevertheless, there is currently a lack of research on how the introduction of different materials affects the sensing properties of these composites. The rapid development of MXene has raised intriguing questions about improving sensor performance by combining MXene with other materials such as polymers, metals and inorganic non-metals. This review will concentrate on the construction of MXene-based composites and explore ways to enhance their sensor applications. Specifically, this review describes why the introduction of materials to the system brings the advantage of low concentration and high sensitivity assays, as well as the MXene-based frameworks that have been recently investigated. Lastly, in order to capture the current trend of MXene-based composites in sensor applications and identify promising research directions, this review will critically evaluate the potential applications of newly developed MXene systems.

Computer aided aptamer selection for fabrication of electrochemical sensor to detect Aflatoxin B1

Aflatoxin B1 (AFB1) is a naturally occurring toxin produced by Aspergillus flavus and Aspergillus parasiticus. The AFB1 is classified as a potent carcinogen and poses significant health risks both to humans and animals. Early detection of the toxin in post-harvest agricultural products will save lives and promote healthy food production. In this study, stratified docking approach was utilized to screen and identify potential aptamers that can bind to AFB1. ssDNA sequences were acquired from the Mendeley dataset, secondary and tertiary structures were predicted through a series of bioinformatics pipelines. Further, the final DNA tertiary structures were minimized and SiteMap algorithm was used to probe and locate binding cavities. According to the final XP docking result, a 34 nt sequence (5'-ATCCTGTGAGGAATGCTCATGCATAGCAAGGGCT-3') aptamer with a docking score of -5.959 kcal/mol was considered for 200 ns MD Simulation. Finally, the screened DNA-aptamer was immobilized over the gold surface based on Au-S chemistry and utilized for the detection of AFB1. The fabricated DNA-aptamer electrode demonstrated a good analytical performance including wide linear range (1.0 to 1000 ng L-1), detection limit (1.0 ng L-1), high stability, and reproducibility.Communicated by Ramaswamy H. Sarma.

MXene-based electrochemical devices applied for healthcare applications

The initial part of the review provides an extensive overview about MXenes as novel and exciting 2D nanomaterials describing their basic physico-chemical features, methods of their synthesis, and possible interfacial modifications and techniques, which could be applied to the characterization of MXenes. Unique physico-chemical parameters of MXenes make them attractive for many practical applications, which are shortly discussed. Use of MXenes for healthcare applications is a hot scientific discipline which is discussed in detail. The article focuses on determination of low molecular weight analytes (metabolites), high molecular weight analytes (DNA/RNA and proteins), or even cells, exosomes, and viruses detected using electrochemical sensors and biosensors. Separate chapters are provided to show the potential of MXene-based devices for determination of cancer biomarkers and as wearable sensors and biosensors for monitoring of a wide range of human activities.

A novel dual-channel immunochromatographic strip using up-conversion nanoparticles for simultaneous detection of AFB1 and ZEN in maize

Due to universal contamination and synergistic toxicity of multiple mycotoxins in foodstuff, reliable and high-throughput detection methods for multiple mycotoxins are urgently needed in corn products. In this study, a novel dual-channel immunochromatographic assay (ICA) based on improved up-conversion nanoparticles (IUCNPs) was developed for rapidly detecting aflatoxin B1 (AFB1) and zearalenone (ZEN). The synthesized IUCNPs doped by 30% Lu3+ showed a larger size, more regular structure, and brighter fluorescence intensity than conventional UCNPs. The limits of detection (LODs) of single-channel ICA test strips for AFB1 and ZEN detection were 0.01 and 0.1 ng/mL, respectively. After the optimization, the dual-channel ICA of AFB1 and ZEN in 10 min was conducted, resulting in low detection limits of 0.025 and 0.1 ng/mL, respectively. Moreover, the built assay was revealed to be highly specific for six other food-contaminated mycotoxins, and exhibited excellent accuracy, with corresponding R2 of 0.9931 and 0.9982 in calibration curves, respectively. Long-term storage experiments indicated that the dual-channel test strips had superior stability and precision. The LODs of AFB1 and ZEN in spiked maize were 0.025 and 0.25 μg/kg, demonstrating great sensitivity and matrix tolerance. Furthermore, the IUNCP-ICA was validated by high-performance liquid chromatography (HPLC) analyses, and a satisfactory consistency was obtained in 15 natural maize samples. Thus, the IUCNPs-ICA proposed in this work realized rapid and sensitive detection of AFB1 and ZEN, providing broad application potential in on-site screening for multiple mycotoxins in agricultural products.

Diagnostic genosensor for detection of rotavirus based on HFGNs/MXene/PPY signal amplification

A novel genosensor was developed for rotavirus specific cDNA sequence detection. The genosensor was comprised of hierarchical flower-like gold nanostructures, MXene, and polypyrrole (HFGNs/MXene/PPY) nanocomposite as a signal amplification tag, specific antisense ssDNA oligonucleotide as a recognition bioelement, and methylene blue (MB) as a redox marker. The morphological and electrochemical features of the biosensor were first tested and optimized and the high performance of the platform was confirmed in terms of sensitivity and reproducibility. Then, 20 rotavirus RNA isolated from clinical and cell-cultured samples (10 positive and 10 negative confirmed by RT-PCR and electrophoresis methods) were evaluated by the genosensor. The analysis results revealed that the genosensor is able to differentiate successfully between the positive and negative control groups. The developed genosensor for rotavirus RNA detection presented an excellent limit of detection of ∼ 0.8 aM and a determination  range of  10^-18 and 10^-7 M. In addition, the ssDNA/HFGNs/MXene/PPY/GCE showed high selectivity and long-term stability of ~ 24 days. Therefore, this novel genosensor would be of great benefit for the clinical diagnosis of rotavirus.

Recent Progress in Screening of Mycotoxins in Foods and Other Commodities Using MXenes-Based Nanomaterials

Mycotoxin pollution in agricultural food products endangers animal and human health during the supply chains, therefore the development of accurate and rapid techniques for the determination of mycotoxins is of great importance for food safety guarantee. MXenes-based nanoprobes have attracted enormous attention as a complementary analysis and promising alternative strategies to conventional diagnostic methods, because of their fascinating features, like high electrical conductivity, various surface functional groups, high surface area, superb thermal resistance, good hydrophilicity, and environmentally-friendlier characteristics. In this study, we outline the state-of-the-art research on MXenes-based probes in detecting various mycotoxins like aflatoxin, ochratoxin, deoxynivalenol, zearalenone, and other toxins as a most commonly founded mycotoxin in the agri-food supply chain. First, we present the diverse synthesis approaches and exceptional characteristics of MXenes. Afterward, based on the detecting mechanism, we divide the biosensing utilizations of MXenes into two subcategories: electrochemical, and optical biosensors. Then their performance in effective sensing of mycotoxins is comprehensively deliberated. Finally, present challenges and prospective opportunities for MXenes are debated.