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Organophosphates (OPs) and carbamates as insecticides, nematicides, fungicides, and herbicides are constantly increasing. Their neurotoxic nature requires careful usage, and misuse can lead to fatalities. OPs classified as 'Class 1′ toxic compounds irreversibly inhibit cholinesterases due to their molecular structure resembling the natural acetylcholine substrate, leading to toxic events in the human brain. Monitoring such chemicals is relevant for agricultural applications and essential for the military sector to ensure the safety of personnel and civilian populations. State-of-the-art analytical detection methods require time-consuming pre-treatments and costly reagents and face challenges associated with pesticide properties like thermal lability, low volatility, and high polarity, which can compromise analysis performance. Advanced systems like electrophoresis or liquid chromatography are used to address these, but these are not well suited for field analysis. Miniaturized colorimetric assays are becoming more popular for various portable devices and kits (i.e., metabolic or blood cell assays) due to their ease of use and practicality. Here, we aimed to establish and optimize a straight-forward paper-based microfluidic acetylcholine esterase inhibition assay for mobile organophosphate detection, laying the groundwork for future microdevice modules to be used in environmental monitoring, public health, and CBRN applications. • Characterization of a microfluidic paper-based acetylcholine inhibition assay parameters for quantitative malathion detection. • Transfer of the optimized protocol to a single-step multiplexed microfluidic device with prestored enzyme and chromogen reservoirs. • Proof-of-concept microdevice study on the inhibitory potential of the organophosphate malathion. [ABSTRACT FROM AUTHOR]

The development of deployable biosensors that monitor the cumulative dose of toxic pesticides is essential to enable monitoring of soil and water exposure in populated areas. Liquid crystal elastomers (LCEs) offer unique potential as cumulative dose biosensors due to their ability to store chemical information within the polymer network that can later be decoded in the form of quantifiable shape changes. Here, we present an LCE-based biosensor for the detection of the organophosphorus pesticide malathion through the immobilization of the hydrolytic enzyme pig liver esterase (PLE). Exposure to malathion was detected via shape change of the LCE from a flat ribbon to a helical structure. Quantification of the helical pitch provided a label free readout that correlated directly with the cumulative dose of malathion and enabled detection of successive doses independent of dosage timing or dilution. The cumulative dose was chemically encoded in the LCE and could be decoded by hydration, even after successive drying and rehydration steps. Importantly, the signal from the LCE was largely insensitive to sensing conditions and to interference from various chemicals. The combined results illustrate the utility of biocatalytic LCEs for monitoring harmful pollutants while allowing continuous and cumulative dose sensing in real-world conditions. [Display omitted] • LCE-based biosensor for malathion detection using pig liver esterase. • Label-free shape-change readout by measuring the ribbon helical pitch. • Malathion cumulative dose is chemically encoded in LCE. • Output can be rapidly encoded/decoded by drying/hydration of LCE. [ABSTRACT FROM AUTHOR]

The combination of electrochemiluminescence (ECL) and molecularly imprinted polymer (MIP) techniques offers distinct for detecting organophosphorus pesticides (OPs). Herein, a novel flake-like nanocomposites Au@Cu:ZIF-8 was successfully synthesized, as to design a molecularly imprinted electrochemiluminescence (MIP-ECL) sensor for the detection of malathion (MAL). The doped Cu2+ as a co-reaction promoter facilitated the generation of the active intermediate SO 4 •− for the cathodic reaction system with K 2 S 2 O 8 as the co-reactant, while AuNPs were used as an excellent catalyst, further enhancing the ECL strength of the overall reaction system. Subsequently, MIP film was formed by the electropolymerization of Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione as a functional monomer and MAL as a template molecule on the electrode surface. Confirmation of this process was achieved through molecular docking technique, which indicated that template molecule and functional monomer were tightly bound through non covalent bonds. The ECL signal was controlled by the elution and incubation of MAL by the MIP, thus establishing a novel method for MAL detection. The sensor showed a good linear relationship in the range of 10 pg/mL to 0.1 μg/mL with a detection limit of 0.18 pg/mL (S/N = 3). Furthermore, the recoveries of MAL detection in apple, cabbage and tomato samples ranged from 91.94% to 104.50%, indicating that the sensor offers potential applications for trace analysis of OPs in food and agricultural products. [Display omitted] • A molecularly imprinted electrochemiluminescence sensor for the detection of malathion was developed. • Co-reaction promoter and noble metal nanoparticles increased sensitivity of sensor. • Interactions between template molecules and functional monomers were verified by molecular docking technique. • Molecularly imprinted polymer exhibited excellent selectivity for malathion. • The linear detection range was 10 pg/mL to 0.1 μg/mL with a detection limit of 0.18 pg/mL. [ABSTRACT FROM AUTHOR]

A non-enzymatic electrochemical sensor based on bimetallic Cu-Co metal-organic gel (MOG) modified glassy carbon electrode (GCE) was reported to achieve super-sensitive malathion detection. Phytic acid-based Cu-Co bimetallic MOG (PA-Cu-Co composite) is a kind of three-dimensional porous material and has a large surface area and superior conductivity due to crosslinked network structure and bimetal composition. The obtained PA-Cu-Co/GCE sensor can easily bond malathion due to the good affinity between Cu element and sulfur groups of malathion, leading to an inhibited redox signal of Cu element in presence of malathion. The electrode reaction was a typical adsorption controlled process. The introduction of Co element not only greatly improves the electron transfer ability but increases surface area and active sites of sensor interface for high affinity of malathion, thus endowing PA-Cu-Co composite with outstanding sensitivity and selectivity. Under optimized operating conditions, the enzyme-free PA-Cu-Co/GCE malathion sensor exhibits good stability and excellent detection performance, with a wide linear range to malathion of 0.5 pM to 5 μM and low detection limit of 0.3 pM. Furthermore, the PA-Cu-Co/GCE sensor showed good recovery in real samples detection, implicating the potential applicability of PA-Cu-Co/GCE sensor in sensitive and selective detection of organophosphorus pesticides (OPs). • 3D porous Cu-Co MOGs. • Large surface area and abundant active sites. • LOD is 0.3 pM. [ABSTRACT FROM AUTHOR]

The high residual nature of organophosphorus pesticides poses a potential risk to the environment and human health through bioaccumulation. Herein, by using Fe 3 O 4 nanoclusters (NCs) as the nucleation center and polyvinyl pyrrolidone as the stabilization layer, Cu-based metal-organic frameworks (Cu-MOFs) were directly grown around Fe 3 O 4 NCs to form core-shell Fe 3 O 4 @Cu-MOFs composites (FCF). Then, the fluorescence properties of FCF were used to construct a fluorescence biosensor for the detection of organophosphorus pesticide residues in vegetables. The bi-enzyme function between acetylcholinesterase and choline oxidase can produce hydrogen peroxide, which can oxidize ferrous ions to ferric ions thus influencing the fluorescence of FCF. Based on the ability of malathion pesticides to inhibit acetylcholinesterase activity, the biosensor demonstrated a linear relationship between the fluorescence intensity and the concentration of the malathion in the range of 5 ng/mL to 50 μg/mL with a detection limit of 4.2 ng/mL. Furthermore, the FCF was combined with agarose gels to realize the visualization detection of malathion. This novel fluorescent nanocomposite offers promising applications for the visual detection of malathion and in situ imaging of vegetables, establishing a new pathway to develop high-performance fluorescent materials for environmental and food safety. • Fe 3 O 4 @Cu-MOFs nanocomposites were synthesized by "bottle-around-ship" strategy. • Fe 3 O 4 @Cu-MOFs nanocomposites exhibited a stable and enhanced fluorescence. • The portable and visual detection of malathion pesticides was realized. • In-situ imaging of pesticide residues on fresh vegetables was performed. [ABSTRACT FROM AUTHOR]

This work will show, for the first time, the absorptive silica-supported polyaniline (PANI) molybdenum trioxide (MoO 3) semiconductor hybrid coating onto the optical fiber realizing the concept of lossy mode resonance (LMR) incorporated with molecular imprinting (MIP)-based sensors. The unique optical absorptive and imprinting (IP) properties and possessing a proper refractive index, introducing a versatile optical transducer, were assessed in the detection of Malathion (MAL) to address the rising concern of pesticide residue in crops. The accurate structural and morphological characterization confirmed the rough crystalline and spherical particles for a ternary composite of PANI, SiO 2 , and MoO 3 onto an optical fiber curved surface while spectroscopic analysis confirms the formation of imprinting polymer and desirable absorbance characteristics. The experimental and numerical sensing studies revealed that the proposed sensing probe allows the rapid adsorption/desorption of MAL to the sensing films and highly permeable coating under studying the effective parameters influence. The optimized probe exhibits an excellent performance with the maximum sensitivity of within 14–224 µM with the linearity coefficient of R2 = 0.99 possessing a low limit of detection of 9.1 nM. Additionally, this sensor selectively detects. in the presence of other real species and also showed good recovery in the various corps samples. [Display omitted] • The absorptive MoO 3/ PANI hybrid was successfully coated onto the optical fiber. • This work is realizing the concept of LMR incorporated with MIP-based sensors. • Operating fabrication parameters were fully optimized to detect Malathion. • An excellent performance obtained within 14–224 µM and R2 = 0.99 with LOD 9.1 nM. • This work could be further extended to detect other pesticides in aqueous media. [ABSTRACT FROM AUTHOR]

This study establishes an incredibly simple method for trace detection of malathion (MLT) by using spherical Ag nanoparticles (Ag NPs) based on surface enhanced Raman scatting (SERS). MLT was rapidly hydrolyzed through β-elimination reaction under alkaline condition, then provided a favorable ionic environment for SERS detection by using Lewis acids (LAs), leading to a 305 times maximum additional enhancement, and a limit of detection (LOD) as low as 0.1 ppb was achieved. The different alkaline hydrolysis pathways of MLT and other dithiophosphate organophosphorus molecules was clarified, and the conversion of molecular binding states on nano-surface were determined. The method was successfully applied in various tea samples, a LOD as low as 0.05 ppm was obtained. Due to the complex variation of characteristic peaks intensity, multivariate analysis method was used for quantitative analysis and a high determination coefficient (R2 =0.9573) and good dynamic range of 0.1–5 ppm were obtained. [Display omitted] • SERS sensitivity of MLT in alkaline hydrolysis condition was improved by using Lewis acids. • The alkaline hydrolysis of MLT followed β-elimination reaction rather than S N 2 reaction. • The characteristic peaks intensities were influenced by the binding model on the nano-surface. • Malathion in tea was detected within 5 min with a LOD of 0.05 ppm. • MVA was more suitable for quantitative analysis in multiple characteristic peaks. [ABSTRACT FROM AUTHOR]

Malathion is widely applied in agriculture as one of organophosphorus pesticides (OPs) and easily causes a number of health and environmental problems. Traditional methods for analyzing malathion residues have failed to meet the current requirements of detection. To address this challenge, we designed a colorimetric-based single particle detection (SPD) method to quantify malathion using MnO 2 -coated gold nanoparticles (GNP@MnO 2 NPs) as the probe. In the existence of alkaline phosphatase (ALP), p-aminophenyl phosphate (p-APP) can be hydrolyzed to p-aminophenol (p-AP), which employs as a reductant to induce MnO 2 to Mn2+ and make the gold core exposure. With the dark field optical microscopy (DFM), the color change of the probe can be readily observed at the single particle level. However, malathion is able to inhibit the activity of ALP and makes the color of the probe remain. Thus, the content of malathion can be accurately quantified by monitoring the changes in color and scattering intensity of the probe. The linear range of this assay is 0.001–0.1 ng/mL and the limit of detection (LOD) is as low as 0.82 pg/mL. In addition, degradation of malathion can be achieved due to the interaction between malathion and ALP. Therefore, this strategy offers new insights on the design of an ultrasensitive assay for OPs detection and degradation in the future. • A colorimetric-based single particle detection method was developed to quantify malathion. • This assay was achieved by the inhibition of ALP activity with malathion. • The detection limit can reach 0.82 pg/mL. [ABSTRACT FROM AUTHOR]

Malathion is widely applied in agriculture as one of organophosphorus pesticides (OPs) and easily causes a number of health and environmental problems. Traditional methods for analyzing malathion residues have failed to meet the current requirements of detection. To address this challenge, we designed a colorimetric-based single particle detection (SPD) method to quantify malathion using MnO 2 -coated gold nanoparticles (GNP@MnO 2 NPs) as the probe. In the existence of alkaline phosphatase (ALP), p-aminophenyl phosphate (p-APP) can be hydrolyzed to p-aminophenol (p-AP), which employs as a reductant to induce MnO 2 to Mn2+ and make the gold core exposure. With the dark field optical microscopy (DFM), the color change of the probe can be readily observed at the single particle level. However, malathion is able to inhibit the activity of ALP and makes the color of the probe remain. Thus, the content of malathion can be accurately quantified by monitoring the changes in color and scattering intensity of the probe. The linear range of this assay is 0.001–0.1 ng/mL and the limit of detection (LOD) is as low as 0.82 pg/mL. In addition, degradation of malathion can be achieved due to the interaction between malathion and ALP. Therefore, this strategy offers new insights on the design of an ultrasensitive assay for OPs detection and degradation in the future. • A colorimetric-based single particle detection method was developed to quantify malathion. • This assay was achieved by the inhibition of ALP activity with malathion. • The detection limit can reach 0.82 pg/mL. [ABSTRACT FROM AUTHOR]