A visual peroxidase mimicking aptasensor based on Pt nanoparticles-loaded on iron metal organic gel for fumonisin B1 analysis in corn meal

An Encyclopedic Compendium on Chemosensing Supramolecular Metal-Organic Gels

Chemosensing, an interdisciplinary scientific domain, plays a pivotal role ranging from environmental monitoring to healthcare diagnostics and (inter)national security. Metal-organic gels (MOGs) are recognized for their stability, selectivity, and responsiveness, making them valuable for chemosensing applications. Researchers have explored the development of MOGs based on different metal ions and ligands, allowing for tailored properties and sensitivities, and have even demonstrated their applications as portable sensors such as paper-based test strips for practical use. Herein, several studies related to MOGs development and their applications in the chemosensing field via UV-visible or luminance along with electrochemical approach are presented. These papers explored MOGs as versatile materials with their use in sensing bio or environmental analytes. This review provides a foundational understanding of key concepts, methodologies, and recent advancements in this field, fostering the scientific community.

Magnetic nanoparticle-based immunosensors and aptasensors for mycotoxin detection in foodstuffs: An update

Mycotoxin contamination of food crops is a global challenge due to their unpredictable occurrence and severe adverse health effects on humans. Therefore, it is of great importance to develop effective tools to prevent the accumulation of mycotoxins through the food chain. The use of magnetic nanoparticle (MNP)-assisted biosensors for detecting mycotoxin in complex foodstuffs has garnered great interest due to the significantly enhanced sensitivity and accuracy. Within such a context, this review includes the fundamentals and recent advances (2020-2023) in the area of mycotoxin monitoring in food matrices using MNP-based aptasensors and immunosensors. In this review, we start by providing a comprehensive introduction to the design of immunosensors (natural antibody or nanobody, random or site-oriented immobilization) and aptasensors (techniques for aptamer selection, characterization, and truncation). Meanwhile, special attention is paid to the multifunctionalities of MNPs (recoverable adsorbent, versatile carrier, and signal indicator) in preparing mycotoxin-specific biosensors. Further, the contribution of MNPs to the multiplexing determination of various mycotoxins is summarized. Finally, challenges and future perspectives for the practical applications of MNP-assisted biosensors are also discussed. The progress and updates of MNP-based biosensors shown in this review are expected to offer readers valuable insights about the design of MNP-based tools for the effective detection of mycotoxins in practical applications.

Aptasensors Based on Non-Enzymatic Peroxidase Mimics: Current Progress and Challenges

Immunoassays based on antibodies as recognizing elements and enzymes as signal-generating modules are extensively used now in clinical lab diagnostics, food, and environmental analyses. However, the application of natural enzymes and antibodies has some drawbacks, such as relatively high manufacturing costs, thermal instability, and lot-to-lot variations that lower the reproducibility of results. Oligonucleotide aptamers are able to specifically bind their targets with high affinity and selectivity, so they represent a prospective alternative to protein antibodies for analyte recognition. Their main advantages include thermal stability and long shelf life, cost-efficient chemical synthesis, and negligible batch-to-batch variations. At the same time, a wide variety of non-protein peroxidase mimics are now available that show strong potential to replace protein enzymes. Here, we review and analyze non-protein biosensors that represent a nexus of these two concepts: aptamer-based sensors (aptasensors) with optical detection (colorimetric, luminescent, or fluorescent) based on different peroxidase mimics, such as DNAzymes, nanoparticles, or metal-organic frameworks.

Rapid colorimetric sensor for ultrasensitive and highly selective detection of Fumonisin B1 in cereal based on laccase-mimicking activity of silver phosphate nanoparticles

Ag3PO4 nanoparticles (NPs) was prepared through a facile coprecipitation method, and was first found to have excellent laccase-mimicking catalytic activity. The study confirms that Fumonisin B1 (FB1) can effectively hinder the production of superoxide anion (O2-) between Ag3PO4 NPs and dissolved oxygen, and further inhibit laccase-mimicking activity of Ag3PO4 NPs. Thus, a novel rapid colorimetric sensor for FB1 analysis in cereal was first established using laccase-mimicking activity as sensing signal. The absorbance variation of sensing solution is directly related to the amount of FB1, and the color change is further combined with smartphone for quantitively analysis of FB1. The limit of detection (LOD) of the sensor is determined as low as 1.73 μg·L-1, which is far lower than the maximum residue limits (MRLs) of FB1 set by European Commission and US Food and Drug Administration (FDA). The average recovery of 87.8-104.5% for FB1 detection was obtained in cereal.

Galvanic Bipolar Electrode Arrays with Self-Driven Optical Readouts

In this work, we report a bipolar electrode (BPE) array system with self-driven optical readouts of the faradic current flowing through the BPEs. The BPE array system is based on the spontaneous redox reactions that are respectively occurring at opposite poles of the BPEs with appropriate electrocatalysts on the poles; this system is analogous to one consisting of galvanic electrochemical cells. The galvanic BPE array system operates in a self-powered mode that requires there to be neither a direct electrical connection nor external electrical polarization to each BPE. Importantly, the appropriate electrocatalysts on the poles play a critical role in the galvanic BPE array system to induce the spontaneous redox reactions occurring at the poles of BPEs. Moreover, the galvanic BPE array system provides self-driven optical readouts, including fluorometric and colorimetric ones, to report the faradaic current resulting from the spontaneous redox reactions on the BPE poles. Based on the unique benefits that the galvanic BPE array system has over conventional BPEs, we demonstrated the promising potential of galvanic BPE arrays for the simple yet rapid and quantitative screening of electrocatalysts for the oxygen reduction reaction as well as sensitive sensing of H2O2 in parallel.

Nanoscale Materials Applying for the Detection of Mycotoxins in Foods

Trace amounts of mycotoxins in food matrices have caused a very serious problem of food safety and have attracted widespread attention. Developing accurate, sensitive, rapid mycotoxin detection and control strategies adapted to the complex matrices of food is crucial for in safeguarding public health. With the continuous development of nanotechnology and materials science, various nanoscale materials have been developed for the purification of complex food matrices or for providing response signals to achieve the accurate and rapid detection of various mycotoxins in food products. This article reviews and summarizes recent research (from 2018 to 2023) on new strategies and methods for the accurate or rapid detection of mold toxins in food samples using nanoscale materials. It places particular emphasis on outlining the characteristics of various nanoscale or nanostructural materials and their roles in the process of detecting mycotoxins. The aim of this paper is to promote the in-depth research and application of various nanoscale or structured materials and to provide guidance and reference for the development of strategies for the detection and control of mycotoxin contamination in complex matrices of food.

Comprehensive insight into adsorption of chlortetracycline hydrochloride by room-temperature synthesized water-stable Zr-based metal-organic gel/sodium alginate beads

Chlortetracycline hydrochloride (CTC) is one of the prevailing antibiotic pollutants that harm both environmental ecosystem and human health. Herein, Zr-based metal-organic gels (Zr-MOGs) with lower-coordinated active sites and hierarchically porous structures are fabricated via a facile straightforward room-temperature strategy for CTC treatment. More importantly, we incorporated the powder Zr-MOGs into low-cost sodium alginate (SA) matrix to achieve shaped Zr-based metal-organic gel/SA beads for enhancing the adsorption ability and ameliorating the recyclability. The Langmuir maximum adsorption capacities of Zr-MOGs and Zr-MOG/SA beads could reach 143.9 mg/g and 246.9 mg/g, respectively. What's more, in the manual syringe unit and continuous bead column experiments, Zr-MOG/SA beads could achieve an eluted CTC removal ratio as high as 93.6% and 95.5% in the real water sample, respectively. On top of that, the adsorption mechanisms were put forward as a combination of pore filling, electrostatic interaction, hydrophilic-lipophilic balance, coordination, π-π interaction as well as hydrogen bonding interaction. This study outlines a workable strategy for the facile preparation of candidate adsorbents for wastewater treatment.

Novel electrochemiluminescence biosensor of fumonisin B1 detection using MWCNTs-PDMS flexible bipolar electrode

A novel portable and disposable bipolar electrode (BPE)-electrochemiluminescence (ECL) device was fabricated for fumonisin B₁ (FB₁) detection. BPE was fabricated by using MWCNTs and polydimethylsiloxane (PDMS) due to their excellent electrical conductivity and good mechanical stiffness. After the deposition of Au NPs on the cathode of BPE, the ECL signal could be improved 89-fold. Then a specific aptamer-based sensing strategy was constructed by grafting capture DNA on Au surface, followed by hybridizing with aptamer. Meanwhile, an excellent catalyst, Ag NPs was labeled on aptamer to activate oxygen reduction reaction, leading to a 13.8-fold enhancement in ECL signal at the anode of BPE. Under the optimal conditions, the biosensor exhibited a wide linear range of 0.10 pg/mL to 10 ng/mL for FB₁ detection. Meanwhile, it demonstrated satisfactory recoveries for real sample detection with good selectivity, making it to be a convenient and sensitive device for mycotoxin assay.

An In Situ Study on Nanozyme Performance to Optimize Nanozyme-Strip for Aβ Detection

The nanozyme-strip is a novel POCT technology which is different from the conventional colloidal gold strip. It primarily utilizes the catalytic activity of nanozyme to achieve a high-sensitivity detection of target by amplifying the detection signal. However, previous research has chiefly focused on optimizing nanozyme-strip from the perspective of increasing nanozyme activity, little is known about other physicochemical factors. In this work, three sizes of Fe₃O₄ nanozyme and three sizes of CoFe₂O₄ nanozyme were used to investigate the key factors of nanozyme-strip for optimizing and improving its detection performance. We found that three sizes of Fe₃O₄ nanozyme all gather at the bottom of the nitrocellulose (NC) membrane, and three sizes of CoFe₂O₄ nanozyme migrate smoothly on the NC membrane, respectively. After color development, the surface of NC membranes distributed with CoFe₂O₄ peroxidase nanozymes had significant color change. Experimental results show that CoFe₂O₄ nanozymes had better dispersity than Fe₃O₄ nanozymes in an aqueous solution. We observed that CoFe₂O₄ nanozymes with smaller particle size migrated to the middle of the NC membrane with a higher number of particles. According to the results above, 55 ± 6 nm CoFe₂O₄ nanozyme was selected to prepare the nanozyme probe and achieved a highly sensitive detection of Aβ42Os on the nanozyme-strip. These results suggest that nanozyme should be comprehensively evaluated in its dispersity, the migration on NC membrane, and the peroxidase-like activity to determine whether it can be applied to nanozyme-strip.