Multivariate nanocomposites for electrochemical sensing in the application of food

From traditional to modern: Nanotechnology-driven innovation in mycotoxin sensing for Chinese herbal medicines

Mycotoxin contamination in Chinese herbal medicines (CHMs) is a pressing concern that jeopardizes their quality and safety, despite their widespread therapeutic use. Conventional detection methods are often limited by complexity, cost, and sensitivity, particularly in resource-limited settings. This gap in effective and efficient mycotoxin detection necessitates a comprehensive review that explores innovative solutions to enhance the safety and efficacy of CHMs. Advancements in nanomaterials and related advanced sensing techniques have emerged as a beacon of hope. Therefore, this review aims to fill the knowledge gap by providing a comprehensive overview of the latest developments in mycotoxin detection in CHMs, spotlighting the transformative role of nanomaterials and advanced sensing techniques. This review stands out for its in-depth exploration of functional nanomaterials across dimensions and their innovative applications in mycotoxin detection. Its innovation stems from a holistic approach that not only surveys current technologies but also charts a forward-looking path, emphasizing novel nanomaterial development, refined pretreatment, and advanced biosensing for on-site detection. It delves into the integration of nanomaterials with advanced sensing technologies, discussing the advantages and limitations of these approaches. A significant innovation of this review lies in the nuanced integration of nanomaterials with machine learning and artificial intelligence, revealing untapped potential for accuracy enhancement. Through this synthesis of knowledge, we hope to inspire further research and development in this critical area, ensuring the continued safe use of CHMs in traditional medicine practices.

Recent Advancements in Electrochemical Sensors Based on MOFs and Their Derivatives

Metal-organic frameworks (MOFs) are composed of metal nodes and organic linkers that can self-assemble into an infinite network. The high porosity and large surface area of MOFs facilitate the effective enrichment and mass transfer of analytes, which can enhance the signal response and improve the sensitivity of electrochemical sensors. Additionally, MOFs and their derivatives possess the properties of unsaturated metal sites and tunable structures, collectively demonstrating their potential for electrochemical sensing. This paper summarizes the preparation methods, structural properties, and applications of MOFs and their derivatives in electrochemical sensing, emphasizing sensors' selectivity and sensitivity from the perspectives of direct and indirect detection. Additionally, it also explores future directions and prospects for MOFs in electrochemical sensing, with the aim of overcoming current limitations through innovative approaches.

Reaction mechanism and detecting properties of a novel molecularly imprinted electrochemical sensor for microcystin based on three-dimensional AuNPs@MWCNTs/GQDs

Microcystins with leucine arginine (MC-LR) is a virulent hepatotoxin, which is commonly present in polluted water with its demethylated derivatives [Dha7] MC-LR. This study reported a low-cost molecularly imprinted polymer network-based electrochemical sensor for detecting MC-LR. The sensor was based on a three-dimensional conductive network composed of multi-walled carbon nanotubes (MWCNTs), graphene quantum dots (GQDs), and gold nanoparticles (AuNPs). The molecularly imprinted polymer was engineered by quantum chemical computation utilizing p-aminothiophenol (p-ATP) and methacrylic acid (MAA) as dual functional monomers and L-arginine as a segment template. The electrochemical reaction mechanism of MC-LR on the sensor was studied for the first time, which is an irreversible electrochemical oxidation reaction involving an electron and two protons, and is controlled by a mixed adsorption-diffusion mechanism. The sensor exhibited a great detection response to MC-LR in the linear range of 0.08-2 μg/L, and the limit of detection (LOD) is 0.0027 μg/L (S/N = 3). In addition, the recoveries of the total amount of MC-LR and [Dha7] MC-LR in the actual sample by the obtained sensor were in the range from 91.4 to 116.7%, which indicated its great potential for environmental detection.

Recent Progress in Non-Enzymatic Electroanalytical Detection of Pesticides Based on the Use of Functional Nanomaterials as Electrode Modifiers

This review presents recent advances in the non-enzymatic electrochemical detection and quantification of pesticides, focusing on the use of nanomaterial-based electrode modifiers and their corresponding analytical response. The use of bare glassy carbon electrodes, carbon paste electrodes, screen-printed electrodes, and other electrodes in this research area is presented. The sensors were modified with single nanomaterials, a binary composite, or triple and multiple nanocomposites applied to the electrodes' surfaces using various application techniques. Regardless of the type of electrode used and the class of pesticides analysed, carbon-based nanomaterials, metal, and metal oxide nanoparticles are investigated mainly for electrochemical analysis because they have a high surface-to-volume ratio and, thus, a large effective area, high conductivity, and (electro)-chemical stability. This work demonstrates the progress made in recent years in the non-enzymatic electrochemical analysis of pesticides. The need for simultaneous detection of multiple pesticides with high sensitivity, low limit of detection, high precision, and high accuracy remains a challenge in analytical chemistry.

Materials Approaches for Improving Electrochemical Sensor Performance

Electrochemical sensors have emerged as important diagnostic tools in recent years, due to their simplicity and ease of use. Compared to instrumental analysis methods that use complicated experimental and data analysis techniques─such as mass spectrometry, nuclear magnetic resonance (NMR), spectrophotometric methods, and chromatography─electrochemical sensors show promise for use in a wide range of real-time and in situ applications such as pharmaceutical testing, environmental monitoring, and medical diagnostics. In order to identify analytes in complex and/or biological samples, materials used for both the electrode materials and the chemically selective layer have been evolving throughout the years for optimizing the analytical performance of electrochemical sensors to increase sensitivity, selectivity and linear range. In this Perspective, attention will be focused on different types of materials that have been used for electrochemical sensing, including new combinations of well-studied materials as well as novel strategies to enhance the performance of sensing devices. The Perspective will also discuss existing challenges in the field and future strategies for addressing those challenges.

Azaporphyrins Embedded on Carbon-Based Nanomaterials for Potential Use in Electrochemical Sensing-A Review

Phthalocyanines and porphyrazines as macrocyclic aza-analogues of well-known porphyrins were deposited on diverse carbon-based nanomaterials and investigated as sensing devices. The extended π-conjugated electron system of these macrocycles influences their ability to create stable hybrid systems with graphene or carbon nanotubes commonly based on π-π stacking interactions. During a 15-year period, the electrodes modified by deposition of these systems have been applied for the determination of diverse analytes, such as food pollutants, heavy metals, catecholamines, thiols, glucose, peroxides, some active pharmaceutical ingredients, and poisonous gases. These procedures have also taken place, on occasion, in the presence of various polymers, ionic liquids, and other moieties. In the review, studies are presented that were performed for sensing purposes, involving azaporphyrins embedded on graphene, graphene oxide or carbon nanotubes (both single and multi-walled ones). Moreover, possible methods of electrode fabrication, limits of detection of each analyte, as well as examples of macrocyclic compounds applied as sensing materials, are critically discussed.

Covalent immobilization of delipidated human serum albumin on poly(pyrrole-2-carboxylic) acid film for the impedimetric detection of perfluorooctanoic acid

The immobilization of biomolecules at screen printed electrodes for biosensing applications is still an open challenge. To enrich the toolbox of bioelectrochemists, graphite screen printed electrodes (G-SPE) were modified with an electropolymerized film of pyrrole-2-carboxilic acid (Py-2-COOH), a pyrrole derivative rich in carboxylic acid functional groups. These functionalities are suitable for the covalent immobilization of biomolecular recognition layers. The electropolymerization was first optimized to obtain stable and conductive polymeric films, comparing two different electrolytes: sodium dodecyl sulphate (SDS) and sodium perchlorate. The G-SPE modified with Py-2-COOH in 0.1 M SDS solution showed the required properties and were further tested. A proof-of-concept study for the development of an impedimetric sensor for perfluorooctanoic acid (PFOA) was carried out using the delipidated human serum albumin (hSA) as bioreceptor. The data interpretation was supported by size exclusion chromatography and small-angle X-ray scattering (SEC-SAXS) analysis of the bioreceptor-target complex and the preliminary results suggest the possibility to further develop this biosensing strategy for toxicological and analytical studies.