Acetylcholinesterase electrochemical biosensors with graphene-transition metal carbides nanocomposites modified for detection of organophosphate pesticides

Recent advances and challenges in graphene-based electrochemical biosensors for food safety

Ensuring food safety is a critical global concern, particularly in light of recent pandemics and rising contamination risks from pesticides, antibiotics, toxins, and allergens. These contaminants pose significant health hazards, including neurological disorders, endocrine disruption, antibiotic resistance, and carcinogenic effects. Regulatory agencies such as the Food and Agriculture Organization (FAO), the World Health Organization (WHO), and the United States Food and Drug Administration (FDA) have established strict maximum residue limits (MRLs) to mitigate these risks. However, enforcement remains challenging due to limitations in current detection methods. The increasing global population and limited food resources have exacerbated food security challenges, while contaminants can infiltrate food at various stages, including production, processing, and packaging. Despite consumer awareness, significant amounts of food are discarded due to quality concerns. To address these issues, researchers are actively developing low-cost, reliable sensing technologies for real-time food quality assessment and contamination detection. Among these, graphene-based electrochemical biosensors have emerged as a promising solution due to their high sensitivity, selectivity, and cost-effectiveness. This review provides an in-depth analysis of recent advancements in graphene-based electrochemical biosensors, focusing on their role in detecting foodborne hazards and improving food quality monitoring. By integrating selective layers, these sensors enhance detection efficiency and provide an innovative solution for safeguarding public health. The findings underscore the transformative potential of graphene-derived biosensors in food safety diagnostics, paving the way for more reliable and sustainable food monitoring systems.

Ti3C2 MXene/MoS2@AuNPs ternary nanocomposite for highly sensitive electrochemical detection of phoxim residues in fruits

Phoxim, extensively utilized in agriculture as an organothiophosphate insecticide, has the potential to cause neurotoxicity and pose human health hazards. In this study, an electrochemical enzyme biosensor based on Ti3C2 MXene/MoS2@AuNPs/AChE was constructed for the sensitive detection of phoxim. The two-dimensional multilayer structure of Ti3C2 MXene provides a robust framework for MoS2, leading to an expansion of the specific surface area and effectively preventing re-stacking of Ti3C2 MXene. Additionally, the synergistic effect of self-reduced grown AuNPs with MoS2 further improves the electrical conductivity of the composites, while the robust framework provides a favorable microenvironment for immobilization of enzyme molecules. Ti3C2 MXene/MoS2@AuNPs electrochemical enzyme sensor showed a significant response to phoxim in the range of 1 × 10-13 M to 1 × 10-7 M with a detection limit of 5.29 × 10-15 M. Moreover, the sensor demonstrated excellent repeatability, reproducibility, and stability, thereby showing its promising potential for real sample detection.

Silica-Ti3C2Tx MXene Nanoarchitectures with Simultaneous Adsorption and Photothermal Properties

Layered Ti3C2Tx MXene has been successfully intercalated and exfoliated with the simultaneous generation of a 3D silica network by treating its cationic surfactant intercalation compound (MXene-CTAB) with an alkoxysilane (TMOS), resulting in a MXene-silica nanoarchitecture, which has high porosity and specific surface area, together with the intrinsic properties of MXene (e.g., photothermal response). The ability of these innovative MXene silica materials to induce thermal activation reactions of previously adsorbed compounds is demonstrated here using NIR laser irradiation. For this purpose, the pinacol rearrangement reaction has been selected as a first model example, testing the effectiveness of NIR laser-assisted photothermal irradiation in these processes. This work shows that Ti3C2Tx-based nanoarchitectures open new avenues for applications that rely on the combined properties inherent to their integrated nanocomponents, which could be extended to the broader MXene family.

Modern analytical and bioanalytical technologies and concepts for smart and precision farming

Unpredictable natural disasters, disease outbreaks, climate change, pollution, and war constantly threaten food crop production. Smart and precision farming encourages using information or data obtained by using advanced technology (sensors, AI, and IoT) to improve decision-making in agriculture and achieve high productivity. For instance, weather prediction, nutrient information, pollutant assessment, and pathogen determination can be made with the help of new analytical and bioanalytical methods, demonstrating the potential for societal impact such as environmental, agricultural, and food science. As a rising technology, biosensors can be a potential tool to promote smart and precision farming in developing and underdeveloped countries. This review emphasizes the role of on-field, in vivo, and wearable biosensors in smart and precision farming, especially those biosensing systems that have proven with suitably complex and analytically challenging samples. The development of various agricultural biosensors in the past five years that fulfill market requirements such as portability, low cost, long-term stability, user-friendliness, rapidity, and on-site monitoring will be reviewed. The challenges and prospects for developing IoT and AI-integrated biosensors to increase crop yield and advance sustainable agriculture will be discussed. Using biosensors in smart and precision farming would ensure food security and revenue for farming communities.

Recent Advances of Enzyme-Free Electrochemical Sensors for Flexible Electronics in the Detection of Organophosphorus Compounds: A Review

Emerging materials integrated into high performance flexible electronics to detect environmental contaminants have received extensive attention worldwide. The accurate detection of widespread organophosphorus (OP) compounds in the environment is crucial due to their high toxicity even at low concentrations, which leads to acute health concerns. Therefore, developing rapid, highly sensitive, reliable, and facile analytical sensing techniques is necessary to monitor environmental, ecological, and food safety risks. Although enzyme-based sensors have better sensitivity, their practical usage is hindered due to their low specificity and stability. Therefore, among various detection methods of OP compounds, this review article focuses on the progress made in the development of enzyme-free electrochemical sensors as an effective nostrum. Further, the novel materials used in these sensors and their properties, synthesis methodologies, sensing strategies, analytical methods, detection limits, and stability are discussed. Finally, this article summarizes potential avenues for future prospective electrochemical sensors and the current challenges of enhancing the performance, stability, and shelf life.

Electrochemical biosensor based on cellulose nanofibers/graphene oxide and acetylcholinesterase for the detection of chlorpyrifos pesticide in water and fruit juice†

In this work, cellulose nanofibers and graphene oxide are used to fabricate a simple and reliable electrochemical biosensor, based on acetylcholinesterase (AChE) for the detection of highly dangerous organophosphates (OPs), utilizing chlorpyrifos as a representative sample. AChE is an enzyme that is essential for neurotransmission and catalyzes the conversion of acetylcholine (ATCh) into thiocholine and acetic acid. The pesticide used in this work, chlorpyrifos, inhibits the catalytic activity of AChE on ATCh, and this inhibition can be measured using square wave voltammetry (SWV). Utilizing a process of surface modification, layers of cellulose nanofibers, graphene oxide, a chitosan-graphene oxide composite, and acetylcholinesterase (AChE/CS-GO/GO/CNFs) were immobilized on a screen-printed carbon electrode (SPCE). The modified SPCE working electrode was characterized using scanning electron microscopy and graphene oxide trapped in the cellulose nanofibers was found to increase the sensitivity of the biosensor. The modified biosensor demonstrated good performance for detection of chlorpyrifos over a linear range of 25–1000 nM under optimum conditions, and the limits of detection and quantification were 2.2 nM and 73 nM, respectively. Our sophisticated technique might offer a more precise, straightforward, quick, and environmentally friendly way to assess chlorpyrifos contamination in water and juice samples.

Cellulose nanofibers and graphene oxide are used to fabricate an electrochemical biosensor based on acetylcholinesterase for detecting organophosphates. This biosensor is simple and reliable, and it utilizes chlorpyrifos as a representative sample of highly dangerous OPs.

Hybrid Nanobioengineered Nanomaterial-Based Electrochemical Biosensors

Nanoengineering biosensors have become more precise and sophisticated, raising the demand for highly sensitive architectures to monitor target analytes at extremely low concentrations often required, for example, for biomedical applications. We review recent advances in functional nanomaterials, mainly based on novel organic-inorganic hybrids with enhanced electro-physicochemical properties toward fulfilling this need. In this context, this review classifies some recently engineered organic-inorganic metallic-, silicon-, carbonaceous-, and polymeric-nanomaterials and describes their structural properties and features when incorporated into biosensing systems. It further shows the latest advances in ultrasensitive electrochemical biosensors engineered from such innovative nanomaterials highlighting their advantages concerning the concomitant constituents acting alone, fulfilling the gap from other reviews in the literature. Finally, it mentioned the limitations and opportunities of hybrid nanomaterials from the point of view of current nanotechnology and future considerations for advancing their use in enhanced electrochemical platforms.

A novel construct of an electrochemical acetylcholinesterase biosensor for the investigation of malathion sensitivity to three different insect species using a NiCr2O4/g-C3N4 composite integrated pencil graphite electrode

Herein, an electrochemical biosensor has been prepared to assess the sensitivity of an organophosphate insecticide, malathion, to acetylcholinesterase (AChE) enzyme of three insects including Apis mellifera (honeybee), Tribolium castaneum (red flour beetle), and Zootermopsis nevadensis (dampwood termite). A composite of nickel chromite (NiCr2O4) and graphitic carbon nitride (g-C3N4) was prepared and characterized for its morphological, chemical and electrical properties. The NiCr2O4/g-C3N4 composite integrated pencil graphite electrodes were used to covalently immobilize insect AChE enzymes and amperometric response of bioelectrodes was determined through cyclic voltammetry. The prepared bioelectrodes exhibited high enzyme immobilization efficiency and electro-catalytic performance. The integrated bioelectrodes could efficiently detect malathion induced inhibition of insects' AChEs. The linear ranges for malathion were found to be 0.1-1.6 μM, 1-40 nM and 2-100 nM, and LODs were 2 nM, 0.86 nM and 2.3 nM for A. mellifera, T. castaneum, and Z. nevadensis, respectively. Additionally, the biosensing platform developed using A. mellifera AChE was found highly sensitive and effective for malathion recoveries from spiked wheat flour samples with high recovery rates. Moreover, the proposed method was adequately reproducible and selective. The results revealed that A. mellifera AChE is less sensitive to inhibition by malathion as compared to T. castaneum, and Z. nevadensis AChE. The experimental results were validated through computational docking of malathion with insect AChEs and the results were in correspondence to experimental outcomes. The proposed method can be a plausible alternate to conventional analytical methods to assess the pesticide sensitivity and toxicity of various compounds against insect enzymes.

Electrochemical (Bio)Sensors for the Detection of Organophosphorus Pesticides Based on Nanomaterial-Modified Electrodes: A Review

Organophosphorus pesticides were easily remained in fruits and vegetables which would be harm to the environmental safety and human health. In recent years, due to the simple preparation process, fast response and high sensitivity, the electrochemical (bio)sensors have received increasing attention, which were extensively used as the sensing platform for the detection of OPPs. The mechanisms for the determination of OPPs mainly included redox of nitrophenyl OPPs, enzyme hydrolysis and inhibition, immunosensor, aptasensor. Nowadays, the mainly explored electrode material has focused on metal-organic frameworks, metal and metal derivatives, carbon materials (carbon nanotube, graphene, g-C3N4), MXene, etc. These nanomaterials played important roles in the electrochemical (bio)sensors, which included: (a) as an electrocatalyst to promote the redox reaction, (b) as a carrier to load the enzyme or aptamer, (c) as a recognizer to identify the targets. The nanomaterials-based electrochemical (bio)sensor was a rapid, cost-effective methods to detect OPPs with high sensitivity. Besides, this review compared the analytical performance of different nanomaterials-based electrochemical (bio)sensors, and also identified the key challenges in the future. It would provide new ideas and insights to the further development and application of electrochemical (bio)sensors and the detection of pesticides in real samples.

MXene-based electrochemical and biosensing platforms to detect toxic elements and pesticides pollutants from environmental matrices

Fabricating new biosensing constructs with high selectivity and sensitivity is the most needed environmental detection tool. In this context, several nanostructured materials have been envisaged to construct biosensors to achieve superior selectivity and sensitivity. Among them, MXene is regarded as the most promising to develop biosensors due to its fascinating attributes, like high surface area, excellent thermal resistance, good hydrophilicity, unique layered topology, high electrical conductivity, and environmentally-friendlier properties. MXenes-based materials have emerged as a prospective for catalysis, energy storage, electronics, and environmental sensing and remediation applications thanks to the above-mentioned exceptional characteristics. This review elaborates on the contemporary and state-of-the-art advancements in MXene-based electrochemical and biosensing tools to detect toxic elements, pharmaceutically active residues, and pesticide contaminants from environmental matrices. At first, the surface functionalization/modification of MXenes is discussed. Afterwards, a particular focus has been devoted to exploiting MXene to construct electrochemical (bio) sensors to detect various environmentally-related pollutants. Lastly, current challenges in this arena accompanied by potential solutions and directions are also outlined.

A 3D printable adapter for solid-state fluorescence measurements: the case of an immobilized enzymatic bioreceptor for organophosphate pesticides detection

The widespread use of pesticides in the last decades and their accumulation into the environment gave rise to major environmental and human health concerns. To address this topic, the scientific community pointed out the need to develop methodologies to detect and measure the presence of pesticides in different matrices. Biosensors have been recently explored as fast, easy, and sensitive methods for direct organophosphate pesticides monitoring. Thus, the present work aimed at designing and testing a 3D printed adapter useful on different equipment, and a membrane support to immobilize the esterase-2 from Alicyclobacillus acidocaldarius (EST2) bioreceptor. The latter is labelled with the IAEDANS, a bright fluorescent probe. EST2 was selected since it shows a high specificity toward paraoxon. Our results showed good stability and replicability, with an increasing linear fluorescent intensity recorded from 15 to 150 pmol of labelled EST2. Linearity of data was also observed when using the immobilized labelled EST2 to detect increasing amounts of paraoxon, with a limit of detection (LOD) of 0.09 pmol. This LOD value reveals the high sensitivity of our membrane support when mounted on the 3D adapter, comparable to modern methods using robotic workstations. Notably, the use of an independent support significantly simplified the manipulation of the membrane during experimental procedures and enabled it to match the specificities of different systems. In sum, this work emphasizes the advantages of using 3D printed accessories adapted to respond to the newest research needs.

Electrochemical biosensor based on CuPt alloy NTs-AOE for the ultrasensitive detection of organophosphate pesticides

The electrode material is vital for the performance of the electrochemical biosensor. Lately, many nanomaterials have been developed to improve the sensitivity and detection efficiency of the biosensors. In this work, a kind of one-dimensional nanomaterials, the CuPt alloy nanotubes with an open end (CuPt alloy NTs-AOE), was explored. The nanotubes with an open end can provide a larger electrochemical active surface area and more active sites for the immobilization of enzyme. The CuPt alloy displays excellent conductivity and catalytic activity. In addition, the Cu shows the great affinity to thio-compounds, which can greatly enhance the detection efficiency and sensitivity. As a result, the prepared biosensor demonstrates the wider linear range of 9.98 × 10^-10-9.98 × 10^-5g l^-1for fenitrothion and 9.94 × 10^-11-9.94 × 10^-4g l^-1for dichlorvos (as model OPs ) and with the lower detection limit of 1.84 × 10^-10g l^-1and 6.31 × 10^-12g l^-1(S/N = 3), respectively. Besides, the biosensor has been used to detect the real samples and obtains satisfactory recoveries (95.58%-100.56%).

Colorimetric Detection of Organophosphate Pesticides Based on Acetylcholinesterase and Cysteamine Capped Gold Nanoparticles as Nanozyme

Organophosphates (OPs) are neurotoxic agents also used as pesticides that can permanently block the active site of the acetylcholinesterase (AChE). A robust and sensitive detection system of OPs utilising the enzyme mimic potential of the cysteamine capped gold nanoparticles (C-AuNPs) was developed. The detection assay was performed by stepwise addition of AChE, parathion ethyl (PE)-a candidate OP, acetylcholine chloride (ACh), C-AuNPs, and 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the buffer solution. The whole sensing protocol completes in 30–40 min, including both incubations. The Transmission Electron Microscopy (TEM) results indicated that the NPs are spherical and have an average size of 13.24 nm. The monomers of C-AuNPs exhibited intense catalytic activity (nanozyme) for the oxidization of TMB, revealed by the production of instant blue colour and confirmed by a sharp peak at 652 nm. The proposed biosensor’s detection limit and linear ranges were 5.8 ng·mL⁻¹ and 11.6–92.8 ng·mL⁻¹, respectively, for PE. The results strongly advocate that the suggested facile colorimetric biosensor may provide an excellent platform for on-site monitoring of OPs.

A Fluidics-Based Biosensor to Detect and Characterize Inhibition Patterns of Organophosphate to Acetylcholinesterase in Food Materials

A chip-based electrochemical biosensor is developed herein for the detection of organophosphate (OP) in food materials. The principle of the sensing platform is based on the inhibition of dimethoate (DMT), a typical OP that specifically inhibits acetylcholinesterase (AChE) activity. Carbon nanotube-modified gold electrodes functionalized with polydiallyldimethylammonium chloride (PDDA) and oxidized nanocellulose (NC) were investigated for the sensing of OP, yielding high sensitivity. Compared with noncovalent adsorption and deposition in bovine serum albumin, bioconjugation with lysine side chain activation allowed the enzyme to be stable over three weeks at room temperature. The total amount of AChE was quantified, whose activity inhibition was highly linear with respect to DMT concentration. Increased incubation times and/or DMT concentration decreased current flow. The composite electrode showed a sensitivity 4.8-times higher than that of the bare gold electrode. The biosensor was challenged with organophosphate-spiked food samples and showed a limit of detection (LOD) of DMT at 4.1 nM, with a limit of quantification (LOQ) at 12.6 nM, in the linear range of 10 nM to 1000 nM. Such performance infers significant potential for the use of this system in the detection of organophosphates in real samples.

2D Transition Metal Carbides (MXene) for Electrochemical Sensing: A Review

MXene, a novel class of 2-dimensional transition metal carbides has evolved as a promising material for various applications owing to its outstanding characteristics such as hydrophilicity, high electrical conductivity, surface area, and attractive topological structure. MXenes can form dispersion in common solvents and constitute composite with other nanomaterials, which can be utilized as effective transducers for molecular sensing. MXene-modified support materials, thus provide an intriguing platform for immobilization of target molecules onto their surface. The literature reveals that it has been increasingly utilized in the sensing of diverse types of analytes including glucose, pharmaceuticals, metals and dyes, cancer markers, pesticides, neurotransmitters, small valuable molecules, and so on. In this review, we summarize the recent updates in the MXene modified materials for sensing. For the convenience of our audience, we have distributed the analytes into categories and discussed them comprehensively. Not only we present the synthesis approach, electrochemical properties and surface chemistry of MXenes but also discussed briefly the current challenges and an outlook for future research in the related area.