Acetylcholinesterase biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine neurotransmitter: A literature review

Recent advances in bioassays for assessing the toxicity of environmental contaminants in effect-directed analysis

Chemical cocktails in the environment can cause adverse impacts on ecosystems and human health even at low concentrations. Effect-directed analysis (EDA) has proven to be very valuable in identifying key toxic substances in environmental mixtures. For this, it is important to carefully select accurate bioassays from a wide range of tests for EDA when applying it to actual environmental samples. This article reviews studies published from 2014 to 2023 that have applied EDA and summarizes the bioassays and their corresponding biological effects. A total of 127 studies were selected from 591 publications evaluating the toxic effects of environmental samples, including wastewater, surface water, and sediments. Here, bioassays used in EDA are summarized, including the assays that measure specific receptor-mediated modes of action (MOA), induction of xenobiotic metabolism pathways, and induction of adaptive stress response pathways using either in vitro or in vivo bioassays. Also, the identified substances using EDA are discussed based on their MOA. The importance of EDA in establishing a comprehensive approach for the detection of environmental contaminants using bioanalytical methods is emphasized. The current limitations and benefits of using EDA in practical applications are outlined and strategies for moving forward are proposed.

Liquid/liquid junction microelectrodes for monitoring cholinergic transmitter in live mice brain in vivo

Acetylcholine (ACh) is an important neurotransmitter and biomarker for neurological disorders. The quantitative detection of ACh in vivo is critical but remains a challenge. In this work, we developed a novel micrometer-sized electrode based on interface between two immiscible electrolyte solutions (ITIES) to achieve in vivo measurement of ACh at high spatiotemporal resolution. The fabricated microITIES electrode was tested in vitro for ACh sensing using electrochemical methods including cyclical voltammetry and i-t amperometry in artificial cerebrospinal fluid (ACSF) solution. An increase in current was observed in both CV and i-t at -0.25 V (vs E1/2, TEA). Both CV and i-t showed a high sensitivity and a linear response with the linear range starting from as low as 0.5 μM. Then the electrode was applied for in vivo measurement of ACh in the living mouse brain. The electrode was implanted in the cortex of the mouse brain via stereotaxic surgery. The electrode was tested for exogenously applied ACh in vivo by local injection of ACh (500 nL, 0.5 M) twice. Repeated cyclic voltammograms were recorded before, during, and after both injections; the cyclic voltammograms showed a significant increase in current at ACh detection potential. The electrode was also tested for endogenously released ACh in vivo by the local injection of a high concentration KCl solution (500 nL and 1000 nL, 100 mM) to stimulate ACh release. Similarly, repeated cyclic voltammograms were recorded before, during, and after both injections; a significant increase in current at the ACh detection potential in the cyclic voltammograms was observed following each injection of KCl. These results validated the capability of the introduced microITIES electrode to measure exogenous and endogenous ACh in vivo.

A DNA tweezer-actuated nanozyme-enzyme hybrid nanoreactor for pesticide detection

The construction of a nanozyme-enzyme hybrid cascade system is an effective protocol to optimize the performance of biosensors. Yet, the integration has limitations due to the lack of harmonious collaboration between nanozyme and enzyme. Herein, we have constructed an efficient enzymatic cascade system by utilizing the base complementary pairing and the targeting capability of DNA tweezers to combine DNA-regulated copper nanoflowers (CuNFs) with acetylcholinesterase (AChE). The DNA tweezers were immobilized onto the CuNFs undergo regular base complementary pairing, and subsequently employed as aptamer to capture AChE gently, forming CuNFs-Apt-AChE cascade system. This system not only enhanced the spatial proximity of CuNFs and AChE to increase cascade catalytic activity, but also demonstrated excellent stability under harsh conditions. Harnessing the nanoarchitecture and characteristics, the CuNFs-Apt-AChE composites were embedded into the hydrogel to fabricate a sensitive biosensor for on-site detecting carbamate pesticides with a detection limit of 0.19 ng mL-1. The hydrogel sensor exhibited high specificity for carbamate pesticides and had been successfully applied in water and juice samples for pesticide detection with strong anti-interference ability. This method holds great potential for the on-site detection of pesticides, offering a new strategy for constructing nanozyme-enzyme cascade hybrid systems with accuracy and sensitivity.

Unlocking the Potential of Origanum Grosii Essential Oils: A Deep Dive into Volatile Compounds, Antioxidant, Antibacterial, and Anti-Enzymatic Properties within Silico Insights

The present study aimed to comprehensively characterize the volatile compounds from the aerial parts of Origanum grosii and evaluate their potential as antioxidants and enzyme inhibitors through both in vitro and in silico approaches. The essential oil's volatile constituents were identified using Gas Chromatography-Mass Spectrometry (GC-MS) analysis, revealing carvacrol (31 %), p-cymene (18.59 %), thymol (12.31 %), and ɣ-terpinene (10.89 %) as the major compounds. The antioxidant capacity was measured using three distinct assays. Notably, Origanum grosii essential oil (OGEO) exhibited significant antioxidant activity, with IC50 values of 55.40±2.23, 81.65±3.26, and 98.04±3.87 μg/mL in DPPH, ABTS, and FRAP assays, respectively. The antibacterial activity was evaluated against both Gram-positive and Gram-negative bacterial strains, including Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa IH, and Listeria monocytogenes ATCC 13932. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the broth microdilution method. The inhibitory effects of OGEO were also assessed against enzymes implicated in human pathologies, including α-glucosidase, α-amylase, tyrosinase, and acetylcholinesterase (AChE). OGEO demonstrated notable inhibitory activity with IC50 values of 49.72±1.64, 60.28±2.13, 97.14±5.15, and 119.42±2.97 μg/mL against elastase, α-glucosidase, tyrosinase, and α-amylase, respectively. Additionally, OGEO exhibited anti-AChE and anti-BChE effects, with values of 7.49±0.83 and 1.91±0.77 mg GALAE/g, respectively. The MIC values were 0.125 μg/mL for E. coli, P. aeruginosa, and S. aureus, and 0.25 μg/mL for L. monocytogenes, while MBC values ranged from 0.25 to 0.5 μg/mL. Compared to chloramphenicol (MIC: 8-16 μg/mL, MBC: 32-64 μg/mL), OGEO showed significantly stronger antibacterial effects. In silico analysis further supported the strong binding affinities of the major compounds to the target enzymes. Overall, OGEO shows promise as a natural agent with potential applications in the food, pharmaceutical, and cosmetic industries.

Ultrasensitive non-enzymatic electrochemical detection of paraoxon-ethyl in fruit samples using 2D Ti3C2Tx/MWCNT-OH

This study reports on the development of a highly sensitive non-enzymatic electrochemical sensor based on a two-dimensional Ti3C2Tx/MWCNT-OH nanocomposite for the detection of paraoxon-based pesticide. The synergistic effect between the Ti3C2Tx nanosheet and the functionalized multi-walled carbon nanotubes enhanced the sensor's conductivity and catalytic activity. The nanocomposite demonstrates superior electrochemical and electroanalytical performance compared to the pristine Ti3C2Tx and MWCNT-OH in detecting paraoxon-ethyl in fruit samples (green and red grapes), with a linear response range from 0.1 to 100 μM, a low limit of detection (LOD) of 10 nM, limit of quantitation (LOQ) of 70 nM, and sensitivity of 0.957 µA μM-1 cm-2 at pH 8. Furthermore, the sensors maintain excellent selectivity and effectiveness in detecting paraoxon-ethyl even in the presence of various interferents, including diazinon, carbaryl, Fe2+, NO2-, NO3-, ascorbic acid, and glucose. The facile fabrication and enhanced sensing capabilities of the Ti3C2Tx/MWCNT-OH nanocomposite position it as a reliable, cost-effective, and sustainable alternative to conventional detection systems for monitoring pesticide residues in agricultural products.

Luminescent Lanthanide Infinite Coordination Polymers for Ratiometric Sensing Applications

Ratiometric lanthanide coordination polymers (Ln-CPs) are advanced materials that combine the unique optical properties of lanthanide ions (e.g., Eu3+, Tb3+, Ce3+) with the structural flexibility and tunability of coordination polymers. These materials are widely used in biological and chemical sensing, environmental monitoring, and medical diagnostics due to their narrow-band emission, long fluorescence lifetimes, and excellent resistance to photobleaching. This review focuses on the composition, sensing mechanisms, and applications of ratiometric Ln-CPs. The ratiometric fluorescence mechanism relies on two distinct emission bands, which provides a self-calibrating, reliable, and precise method for detection. The relative intensity ratio between these bands varies with the concentration of the target analyte, enabling real-time monitoring and minimizing environmental interference. This ratiometric approach is particularly suitable for detecting trace analytes and for use in complex environments where factors like background noise, temperature fluctuations, and light intensity variations may affect the results. Finally, we outline future research directions for improving the design and synthesis of ratiometric Ln-CPs, such as incorporating long-lifetime reference luminescent molecules, exploring near-infrared emission systems, and developing up-conversion or two-photon luminescent materials. Progress in these areas could significantly broaden the scope of ratiometric Ln-CP applications, especially in biosensing, environmental monitoring, and other advanced fields.

Temperature-dependent toxicity and mechanisms of florfenicol on the embryonic development of marine medaka (Oryzias melastigma)

The extensive use of antibiotics and their persistence in the environment have seriously threatened marine ecosystems in recent years. The frequent occurrence of extreme weather due to climate change has also increased the uncertainty of effective toxicity identification and risk assessment of the chemicals of concern. This study aimed to investigate the toxic effects and potential mechanisms of florfenicol (0.5, 10, 100, 500 and 1000 μg/L) on the embryonic development of marine medaka (Oryzias melastigma) through 21-d experiment under three temperature exposure scenarios (20, 25, and 30 °C). Considering embryo development, the highest level of florfenicol at 1000 μg/L decreased the hatching success at 25 °C, whereas the total inhibition of hatching was observed at 20 °C regardless of florfenicol concentrations of concern. The ATP content was inhibited by the highest florfenicol dose at 20 °C, while stimulated ATP content at 20 °C and 30 °C, compared to 25 °C. Fluctuation of temperatures, especially at 20 ℃, induced oxidative stresses, including increased MDA contents and decreased CYP450 and HSP90 contents. For inflammatory response-related genes (nf-κb, nlrx1, pycard, caspase 1, and il-1β), an increase of florfenicol dose led to gene upregulation at 25 °C. Conversely, gene upregulation was also observed for all treatments at 30 °C, while predominantly downregulation was observed for all treatments at 20 °C. For genes related to DNA damage and apoptosis (pi3k, akt, foxo1, tp53, bcl-2, bax, apaf-1, caspase 9, and 3), alterations in gene expression were evident for all florfenicol treatments at both 20 °C and 30 °C. Therefore, this study suggests that the combined effects of florfenicol and temperature may disrupt the normal function of mitochondria, impacting ATP production, thereby inducing oxidative stress, inflammatory response, DNA damage, and apoptosis, ultimately resulting in decreased hatching rates and increased mortality. Furthermore, the key findings of this study reveal the complex interactions between florfenicol and temperature and emphasize the need to consider temperature when identifying toxicity and mechanisms, as well as the ecological risk assessment of florfenicol in marine environments.

Electrochemical sensor for effective detection of methyl parathion applying multidimensional MXene/CNHs/PPy nanocomposite to synergistically immobilize acetylcholinesterase

In this study, a novel acetylcholinesterase (AChE)-based electrochemical sensor was successfully constructed using two-dimensional MXene, carbon nanohorns (CNHs) and polypyrrole (PPy) as the substrate material for the detection of methyl parathion (MP) residue. The multidimensional MXene/CNHs composite, formed through electrostatic self-assembly, provided a high specific surface area and excellent conductivity. With an active surface area of 0.1062 cm2, the composite provided numerous electroactive sites for AChE immobilization and facilitated electron diffusion at the sensing interface, amplifying the electrochemical signals. Additionally, polypyrrole (PPy) improved AChE adhesion on the electrode surface, further enhancing the stability of the sensor. The proposed sensor exhibited a wide linear range (0.002-346 ng mL-1) and low detection limit (0.00021 ng mL-1) for MP. This study offers an innovative strategy to detect MP, showcasing the potential of two-dimensional materials in electrochemical sensing.

A highly specific two-photon fluorescent probe for real-time monitoring of acetylcholinesterase in neurogenic disorders in vivo

Acetylcholinesterase (AChE) hydrolyses choline into thiocholine, which is essential for cholinergic neurons to revert to their resting state following activation. Abnormal changes in AChE activity can directly affect nervous system function. Thus, the specific detection of AChE activity is urgently needed for elucidating the function of the nervous system and diagnosing AChE-related diseases. Current methods for detecting AChE activity have several limitations, including strong background interference and poor tissue penetration. Thus, we designed and synthesized a two-photon (TP) excited fluorescent probe, WZ-AChE, for the specific detection of AChE. Briefly, a carbamate bond was chosen to specifically recognize AChE, which can also be cleaved by AChE. The product, WZ, released strong deep red fluorescence signal under TP excitation at 800 nm. Our results showed that WZ-AChE can detect AChE activity in PC12 cells with both superior sensitivity and selectivity. In addition, we successfully applied WZ-AChE to a C. elegans Parkinson's disease (PD) model and a mouse model of depression. The findings revealed that AChE activity was greater in both disease models than in the control group. To summarize, a novel tool was created to investigate the mechanisms underlying PD and depression.

Parthenogenetic Haemaphysalis longicornis acetylcholinesterases are triggered by the repellent effect of cinnamaldehyde, a primary compound found in cinnamon oil

The control and prevention of ticks and tick-borne diseases rely on chemical insecticides and repellents. Plant-derived compounds potentially represent new and safer repellents. Cinnamaldehyde, a component of cinnamon oil, exhibits antibacterial, anti-inflammatory, acaricidal, and repellent activity against ticks. Here we studied the molecular mechanism of the repellent effect of cinnamaldehyde on Haemaphysalis longicornis. A 2 % cinnamaldehyde treatment resulted in >90 % nymph repellency within 6 h. Nymphs were exposed to cinnamaldehyde for 30 min, and subsequent transcriptome and metabolome analyses revealed the involvement of H. longicornis Acetylcholinesterases (HL-AchEs) in the response process. HL-AchEs was transcribed in all tick developmental stages and tissues. Following cinnamaldehyde treatment, the transcript and specific activity of the enzyme of AchE were significantly altered. Following RNAi, electroantennography (EAG) tests demonstrated a significant decrease in response to various repellents as well as a significant decrease in repellency. Our findings have revealed that HL-AchEs mediates cinnamaldehyde-induced tick repellency, and the results provide insights into the mechanism of plant-derived tick repellents.

DbGTi protein attenuates chromium (VI)-induced oxidative stress via activation of the Nrf2/HO-1 signalling pathway in zebrafish (Danio rerio) larval model

Hexavalent chromium (Cr (VI)) contamination poses a significant threat to environmental and human health due to its ability to induce oxidative stress. Conventional strategies to counter Cr (VI)-induced oxidative stress, like antioxidants and chelating agents, face efficacy limitations and adverse effects. The present study is intended to counteract the limitations of conventional strategies by introducing a trypsin inhibitor isolated from Dioscorea bulbifera L. tubers, known as DbGTi protein, against Cr (VI)-induced developmental toxicity and oxidative stress. Through a comprehensive array of biochemical assays, behavioural tests, and gene expression analyses, this study interprets the underlying mechanisms of the DbGTi protein. Results demonstrated that the DbGTi protein effectively restored antioxidant defense systems, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione S-transferase (GST), and glutathione peroxidase (GTPx), thereby mitigating cellular damage, reducing cell death, and enhancing neuro-biomarkers. qRT-PCR analysis of mRNA expression profiling revealed the upregulation of genes associated with antioxidant defense (sod, cat, gpx) and defense pathway (nrf2, hmox-1a), further highlighting the protective effects of DbGTi protein against Cr (VI)-induced oxidative stress.

Lead induced cerebellar toxicology of developmental Japanese quail (Coturnix japonica) via oxidative stress-based Nrf2/Keap1 pathway inhibition and glutathione-mediated apoptosis signaling activation

Lead (Pb) is a heavy metal that has been recognized as a neurotoxin, meaning it can cause harmful effects on the nervous system. However, the neurotoxicology of Pb to birds still needs further study. In this study, we examined the neurotoxic effects of Pb exposure on avian cerebellum by using an animal model-Japanese quail (Coturnix japonica). The one-week old male chicks were exposed to 50, 200 and 500 mg/kg Pb of environmental relevance in the feed for five weeks. The results showed Pb caused cerebellar microstructural damages charactered by deformation of neuroglia cells, granule cells and Purkinje cells with Nissl body changes. Moreover, cerebellar neurotransmission was disturbed by Pb with increasing acetylcholine (ACh) and decreasing acetylcholinesterase (AChE), dopamine (DA), γ-Aminobutyric Acid (GABA) and Na+/K+ ATPase. Meanwhile, cerebellar oxidative stress was caused by Pb exposure represented by increasing reactive oxygen species (ROS) and malondialdehyde (MDA) as well as decreasing catalase (CAT), glutathione peroxidase (GPX), glutathione (GSH) and superoxide dismutase (SOD). Moreover, RNA-Seq analysis showed that molecular signaling pathways in the cerebellum were disrupted by Pb exposure. In particular, the disruption of nuclear factor erythroid-2-related factor 2 (Nfr2)/kelch-like ECH-associated protein 1 (Keap1) pathway and glutathione metabolism pathway indicated increasing cell apoptosis and functional disorder in the cerebellum. The present study revealed that Pb induced cerebellar toxicology through structural injury, oxidative stress, neurotransmission interference and abnormal apoptosis.

Porphyrin-based covalent organic framework as oxidase mimic for highly sensitive colorimetric detection of pesticides

A covalent organic framework-based strategy was designed for label-free colorimetric detection of pesticides. Covalent organic framework-based nanoenzyme with excellent oxidase-like catalytic activity was synthesized. Unlike other artificial enzymes, porphyrin-based covalent organic framework (p-COF) as the oxidase mimic showed highly catalytic chromogenic activity and good affinity toward TMB without the presence of H2O2, which can be used as substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Based on the fact that the pesticide-aptamer complex can inhibit the oxidase activity of p-COF and reduced the absorbance at 650 nm in UV-Vis spectrum, a label-free and facile colorimetric detection of pesticides was designed and fabricated. Under the optimized conditions, the COF-based colorimetric probe for pesticide detection displayed high sensitivity and selectivity. Taking fipronil for example the limit of detection was 2.7 ng/mL and the linear range was 5 -500,000 ng/mL. The strategy was successfully applied to the detection of pesticides with good recovery , which was in accordance with that of HPLC-MS/MS. The COF-based colorimetric detection was free of complicated modification H2O2, which guaranteed the accuracy and reliability of measurements. The COF-based sensing strategy is a potential candidate for the sensitive detection of pesticides of interests.

State-of-the-art electrochemical biosensors based on covalent organic frameworks and their hybrid materials

As the development of global population and industry civilization, the accurate and sensitive detection of intended analytes is becoming an important and great challenge in the field of environmental, medical, and public safety. Recently, electrochemical biosensors have been constructed and used in sensing fields, such as antibiotics, pesticides, specific markers of cancer, and so on. Functional materials have been designed and prepared to enhance detection performance. Among all reported materials, covalent organic frameworks (COFs) are emerging as porous crystalline materials to construct electrochemical biosensors, because COFs have many unique advantages, including large surface area, high stability, atom-level designability, and diversity, to achieve a far better sensing performance. In this comprehensive review, we not only summarize state-of-the-art electrochemical biosensors based on COFs and their hybrid materials but also highlight and discuss some typical examples in detail. We finally provide the challenge and future perspective of COFs-based electrochemical biosensors.

Core-shell ZnO@CoO nitrogen doped nano-composites as highly sensitive electrochemical sensor for organophosphate pesticides detection

Core-shell ZIF-8@ZIF-67 was synthesized by growing a cobalt-based ZIF-67 on a ZIF-8 seed particle. Herein, through selective etching of the ZIF-8@ZIF-67 core and subsequent direct carbonization, core-shell hollow ZnO@CoO nitrogen-doped nanoporous carbon (HZnO@CoO-NPC) nanocomposites were prepared. HZnO@CoO-NPCs possessed a high nitrogen content, large surface area, high degree of graphitization and excellent electrical conductivity, all of which were attributed to successfully integrating the unique advantages of ZIF-8 and ZIF-67. HZnO@CoO-NPCs were used to assemble acetylcholinesterase (AChE) biosensors for organophosphorus pesticides (OPs) detection. The low detection limit of 2.74 × 10-13 M for chlorpyrifos and 7.6 × 10-15 M for parathion-methyl demonstrated the superior sensing performance. The results showed that the electrochemical biosensor constructed by HZnO@CoO-NPC provided a sensitive and efficient electrochemical strategy for OPs detection.

Exposure to pesticides during pregnancy and the risk of neural tube defects: A systematic review

Exposure to pesticides during pregnancy has been associated with several serious congenital malformations, such as neural tube defects, therefore, is a cause for concern in terms of human health. This review aims to gather information related to maternal exposure during pregnancy and the risk of triggering neural tube defects in the offspring. The search strategy for the studies followed the PRISMA guidelines. We conducted a systematic search in the Science Direct, PubMed, Cochrane Library, Embase, Scopus, and Web of Science databases for all epidemiological studies that sought to associate exposure to pesticides during embryonic development with the risk of neural tube defects (NTDs). The keywords used were "pesticide", "herbicide", "congenital" and "neural". Of the 229 articles, 8 eligible ones (7 case-control and 1 cross-sectional) evaluated pesticide exposure in pregnancy. Different methods were used, including analysis of biological samples and questionnaires. The pesticides studied included insecticides, herbicides, fungicides, and nematicides. Insecticides were the most studied, with variations in concentrations between tissues and studies. Distinct levels of pesticides have been detected in maternal serum, placenta, and umbilical cord. Models were statistically adjusted for confounding factors, such as smoking and dietary supplement intakes. Concentrations were measured in different exposure windows (periconception and prenatal), related to NTDs such as anencephaly and spina bifida. Different data collection techniques, types of biological samples, and exposure windows were used, which made comparison difficult. The main pesticides studied included DDT, DDE, HCH, and endosulfan. Maternal serum showed the highest concentrations of pesticides, but detection in placental tissue and umbilical cord confirms embryonic exposure. Confounding variables were adjusted for in the analysis of the articles, but they may still contribute to the risk of NTDs. All the studies analyzed pesticide exposure and the relationship with NTDs. However, a more standardized survey would be ideal for better comparisons.

Electrochemical Acetylcholinesterase Sensors for Anti-Alzheimer's Disease Drug Determination

Neurodegenerative diseases and Alzheimer's disease (AD), as one of the most common causes of dementia, result in progressive losses of cholinergic neurons and a reduction in the presynaptic markers of the cholinergic system. These consequences can be compensated by the inhibition of acetylcholinesterase (AChE) followed by a decrease in the rate of acetylcholine hydrolysis. For this reason, anticholinesterase drugs with reversible inhibition effects are applied for the administration of neurodegenerative diseases. Their overdosage, variation in efficiency and recommendation of an individual daily dose require simple and reliable measurement devices capable of the assessment of the drug concentration in biological fluids and medications. In this review, the performance of electrochemical biosensors utilizing immobilized cholinesterases is considered to show their advantages and drawbacks in the determination of anticholinesterase drugs. In addition, common drugs applied in treating neurodegenerative diseases are briefly characterized. The immobilization of enzymes, nature of the signal recorded and its dependence on the transducer modification are considered and the analytical characteristics of appropriate biosensors are summarized for donepezil, huperzine A, rivastigmine, eserine and galantamine as common anti-dementia drugs. Finally, the prospects for the application of AChE-based biosensors in clinical practice are discussed.

Present status of insecticide impacts and eco-friendly approaches for remediation-a review

Insecticides are indispensable for modern agriculture to ensuring crop protection and optimal yields. However, their excessive use raises concerns regarding their adverse effects on agriculture and the environment. This study examines the impacts of insecticides on agriculture and proposes remediation strategies. Excessive insecticide application can lead to the development of resistance in target insects, necessitating higher concentrations or stronger chemicals, resulting in increased production costs and disruption of natural pest control mechanisms. In addition, non-target organisms, such as beneficial insects and aquatic life, suffer from the unintended consequences of insecticide use, leading to ecosystem imbalances and potential food chain contamination. To address these issues, integrated pest management (IPM) techniques that combine judicious insecticide use with biological control and cultural practices can reduce reliance on chemicals. Developing and implementing selective insecticides with reduced environmental persistence is crucial. Promoting farmer awareness of responsible insecticide use, offering training and resources, and adopting precision farming technologies can minimize overall insecticide usage.

Fluorescent-Based Neurotransmitter Sensors: Present and Future Perspectives

Neurotransmitters (NTs) are endogenous low-molecular-weight chemical compounds that transmit synaptic signals in the central nervous system. These NTs play a crucial role in facilitating signal communication, motor control, and processes related to memory and learning. Abnormalities in the levels of NTs lead to chronic mental health disorders and heart diseases. Therefore, detecting imbalances in the levels of NTs is important for diagnosing early stages of diseases associated with NTs. Sensing technologies detect NTs rapidly, specifically, and selectively, overcoming the limitations of conventional diagnostic methods. In this review, we focus on the fluorescence-based biosensors that use nanomaterials such as metal clusters, carbon dots, and quantum dots. Additionally, we review biomaterial-based, including aptamer- and enzyme-based, and genetically encoded biosensors. Furthermore, we elaborate on the fluorescence mechanisms, including fluorescence resonance energy transfer, photon-induced electron transfer, intramolecular charge transfer, and excited-state intramolecular proton transfer, in the context of their applications for the detection of NTs. We also discuss the significance of NTs in human physiological functions, address the current challenges in designing fluorescence-based biosensors for the detection of NTs, and explore their future development.

Highly-oxidizing Au@MnO2-X nanozymes mediated homogeneous electrochemical detection of organophosphorus independent of dissolved oxygen

Traditional oxidase-like (OXD) nanozymes rely primarily on O2-mediated superoxide anion (O2·-) process for catalytic oxidation and organophosphorus (Ops) detection. While during the actual detection process, the concentration of O2 is inconstant that can be easily changed with the external environment, distorting detection results. Herein, highly-oxidizing Au@MnO2-X nanozymes with core-shell nanostructure are designed which trigger substantial electron transfer from inner Au core to outer ultrathin MnO2-X layer. According to experimental and theoretical calculations, the core-shell nanostructure and ultrathin MnO2-X of Au@MnO2-X result in the large surface defects, high oxygen vacancies and MnIII ratios. The specially structured Au@MnO2-X nanozymes are therefore highly-oxidizing and the catalytic oxidation can be completed merely through electrons transferring instead of the O2-mediated O2·- process. Based on this, an oxygen independent and ultrasensitive nanozyme-based sensor is established using homogeneous electrochemistry (HEC), its Ops is detected at a LOD of 0.039 ng mL-1. Combined with the UV-vis spectrum of 3,3',5,5'-tetramethylbenzidine (TMB), the linear discriminant analysis of five Ops i.e., Ethion, Omethoate, Diazinon, Chlorpyrifos methyl and Dipterex has achieved superior discrimination results. Therefore, HEC based on strong oxidizing nanozymes provide a new avenue for the development of high-performance electrochemical sensors and demonstrate potential applicability to pesticide residue determination in real samples.

An Updated Review on Electrochemical Nanobiosensors for Neurotransmitter Detection

Neurotransmitters are chemical compounds released by nerve cells, including neurons, astrocytes, and oligodendrocytes, that play an essential role in the transmission of signals in living organisms, particularly in the central nervous system, and they also perform roles in realizing the function and maintaining the state of each organ in the body. The dysregulation of neurotransmitters can cause neurological disorders. This highlights the significance of precise neurotransmitter monitoring to allow early diagnosis and treatment. This review provides a complete multidisciplinary examination of electrochemical biosensors integrating nanomaterials and nanotechnologies in order to achieve the accurate detection and monitoring of neurotransmitters. We introduce extensively researched neurotransmitters and their respective functions in biological beings. Subsequently, electrochemical biosensors are classified based on methodologies employed for direct detection, encompassing the recently documented cell-based electrochemical monitoring systems. These methods involve the detection of neurotransmitters in neuronal cells in vitro, the identification of neurotransmitters emitted by stem cells, and the in vivo monitoring of neurotransmitters. The incorporation of nanomaterials and nanotechnologies into electrochemical biosensors has the potential to assist in the timely detection and management of neurological disorders. This study provides significant insights for researchers and clinicians regarding precise neurotransmitter monitoring and its implications regarding numerous biological applications.