Development of AChE biosensor for the determination of methyl parathion and monocrotophos in water and fruit samples: A cyclic voltammetric study

AuNPs and graphdiyne nanocomposite as robust electrocatalyst for methyl parathion detection in real samples

The present work describes a simple and rapid synthesis method of gold nanoparticles and graphdiyne (AuNPs@GDY) nanocomposites including porous structure. Moreover, the synthesized AuNPs@GDY material was decorated on the glassy carbon electrode (GCE) with a drop coating method to construct a non-enzymatic electrochemical pesticides sensor. The micro-morphology and elemental composition of the materials were characterized by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The electrocatalysis and conductivity of the material were studied with cyclic voltammetry (CV) and impedance method, respectively. The properties of the sensor were investigated by CV and differential pulse voltammetry (DPV). The results showed that AuNPs@GDY exhibited excellent electrocatalytic ability for methyl parathion in a wide linear range (from 0.25 ng/mL to 24.43 μg/mL) and low limit of detection value (6.2 pg/mL). Furthermore, the DPV method used in this paper was accurate and sensitive, and could be used for routine quality control of methyl parathion in kiwi fruit and tomato samples.

Facile synthesis of Au@Ag core-shell nanorod with bimetallic synergistic effect for SERS detection of thiabendazole in fruit juice

This study presented an effective and sensitive SERS substrate for rapid detection of thiabendazole (TBZ) in fruit samples. A core-shell gold/silver nanorod (Au@Ag NRs) has been synthesized as a bimetallic SERS-active substrate. The obtained substrate showed an excellent SERS effect because of the tunable plasmon resonance of Au NRs, the significantly enhanced effect of silver, and the bimetallic synergistic effect of Au@Ag NRs. Under optimal conditions, the substrate was used to detect TBZ in fresh apple juice and peach juice with limits of detection of 0.032 and 0.034 ppm respectively. In addition, the recovery rate was within a satisfactory range of 95-101%, indicating that the Au@Ag NRs substrate could be a SERS detection platform for fruit pesticides residues with great development potential.

VXC-72R/ZrO2/GCE-Based Electrochemical Sensor for the High-Sensitivity Detection of Methyl Parathion

In this work, a carbon black (VXC-72R)/zirconia (ZrO2) nanocomposite-modified glassy carbon electrode (GCE) was designed, and a VXC-72R/ZrO2/GCE-based electrochemical sensor was successfully fabricated for the high-sensitivity detection of methyl parathion (MP). Electrochemical measurements showed that the VXC-72R/ZrO2/GCE-based electrochemical sensor could make full use of the respective advantages of the VXC-72R and ZrO2 nanoparticles to enhance the MP determination performance. The VXC-72R nanoparticles had high electrical conductivity and a large surface area, and the ZrO2 nanoparticles possessed a strong affinity to phosphorus groups, which could achieve good organophosphorus adsorption. On the basis of the synergistic effect generated from the interaction between the VXC-72R and ZrO2 nanoparticles, the VXC-72R/ZrO2/GCE-based electrochemical sensor could show excellent trace analysis determination performance. The low detection limit could reach up to 0.053 μM, and there was a linear concentration range of 1 μM to 100 μM. Such a high performance indicates that the VXC-72R/ZrO2/GCE-based electrochemical sensor has potential in numerous foreground applications.

Catalase based hydrogen peroxide biosensor for mercury determination by inhibition measurements

A new amperometric hydrogen peroxide enzyme inhibition biosensor for the indirect determination of toxic mercury ions, Hg²⁺, based on catalase immobilized on a glassy carbon electrode surface by cross-linking with glutaraldehyde and bovine serum albumin, is reported. The parameters influencing biosensor performance were optimized, including enzyme loading, the amount of hydrogen peroxide, the applied potential and electrolyte pH. It was shown that the inhibition of catalase by Hg²⁺ species is irreversible, with a linear inhibition response between 5×10^-11 and 5×10^-10M. The limit of detection calculated as 10% inhibition was 1.8×10^-11M and is the lowest reported until now. Electrochemical impedance spectroscopy was successfully used as a diagnostic of inhibition. Interferences from other heavy metal ions and organic pesticides were evaluated and the inhibition showed very good selectivity towards Hg²⁺. The method was successfully applied to the determination of mercury ions in different types of water sample.

Design of a macroalgae amperometric biosensor; application to the rapid monitoring of organophosphate insecticides in an agroecosystem

The immobilization of enzymes onto transducer support is a mature technology and has been successfully implemented to improve biocatalytic processes for diverse applications. However, there exists still need to design more sophisticated and specialized strategies to enhance the functional properties of the biosensors. In this work, a biosensor platform based on innovative fabrication strategy was designed, and employed for the detection of organophosphate (OP) in natural waters. The biosensor was prepared by incorporating acetylcholinesterase enzyme (AChE) to the graphite paste modified with tetracyanoquinodimethane (TCNQ) mediator, along with the use of a macroalgae (Cladaphropsis membranous) as a functional immobilization support. The novel immobilization design resulted in a synergic effect, and led to enhanced stability and sensitivity of the biosensor. The designed biosensor was used to analyze methyl parathion OP insecticide in water samples collected from a demonstrably contaminated lake of São Luis Island, Maranhão, Northeast of Brazil. Water analysis revealed that the aquatic ecosystem was polluted by sub-ppm concentrations of the OP insecticide, and a good correlation was found between values obtained through biosensor and GC-MS techniques. Our results demonstrated that macroalgae-biosensor could be used as a low-cost and sensitive screening method to detect target analyte.

Rapid simultaneous detection of multi-pesticide residues on apple using SERS technique

A rapid and straightforward method has been employed to simultaneously detect two pesticides (thiram and methamidophos (MTD)) on apple surface using surface enhanced Raman scattering (SERS) technique. In the experiment, ethanol was dropped onto the contaminated apple surface for pesticide extraction and then gold@silver core-shell nanorods (Au@Ag NRs) were added to generate the SERS signals of the pesticides. Under a laser excitation at 632.8 nm, prominent SERS peaks of blended contaminants were observed, which were chosen to characterize and quantify their concentration. It was found that the SERS intensity of these two peaks changed as a function of the concentration ratio of thiram to MTD. In addition, a better SERS enhancement performance of Au@Ag NRs was demonstrated compared with that of gold nanorods. Our experimental results show that the lowest detectable concentration on apple surfaces is ∼4.6 × 10(-7) M for thiram and ∼4.4 × 10(-4) M for MTD. This study provides a straightforward method for the simultaneous detection of multiple pesticides on fruit surfaces, which is important for food safety and human health.

A molecularly imprinted electrochemical enzymeless sensor based on functionalized gold nanoparticle decorated carbon nanotubes for methyl-parathion detection

Schematic of MP MIP sensor and the possible mechanism.

Acetylcholinesterase biosensors for electrochemical detection of organophosphorus compounds: a review

The exponentially growing population, with limited resources, has exerted an intense pressure on the agriculture sector. In order to achieve high productivity the use of pesticide has increased up to many folds. These pesticides contain organophosphorus (OP) toxic compounds which interfere with the proper functioning of enzyme acetylcholinesterase (AChE) and finally affect the central nervous system (CNS). So, there is a need for routine, continuous, on spot detection of OP compounds which are the main limitations associated with conventional analytical methods. AChE based enzymatic biosensors have been reported by researchers as the most promising tool for analysis of pesticide level to control toxicity and for environment conservation. The present review summarises AChE based biosensors by discussing their characteristic features in terms of fabrication, detection limit, linearity range, time of incubation, and storage stability. Use of nanoparticles in recently reported fabrication strategies has improved the efficiency of biosensors to a great extent making them more reliable and robust.

Determination of currently used pesticides in biota

Although pesticides enable control of the quantity and quality of farm products and food, and help to limit diseases in humans transmitted by insects and rodents, they are regarded as among the most dangerous environmental contaminants because of their tendency to bioaccumulate, and their mobility and long-term effects on living organisms. In the past decade, more analytical methods for accurate identification and quantitative determination of traces of pesticides in biota have been developed to improve our understanding of their risk to ecosystems and humans. Because sample preparation is often the rate-determining step in analysis of pesticides in biological samples, this review first discusses extraction and clean-up procedures, after a brief introduction to the classes, and the methods used in the analysis of pesticides in biota. The analytical methods, especially chromatographic techniques and immunoassay-based methods, are reviewed in detail, and their corresponding advantages, limitations, applications, and prospects are also discussed. This review mainly covers reports published since 2008 on methods for analysis of currently used pesticides in biota.