Recent trends on electrochemical carbon-based nanosensors for sensitive assay of pesticides

Pesticides are substances or mixtures used to prevent, control, and reduce harmful organisms, are divided into various groups as carbamates, organophosphates, organochlorines, pyrethroids, fungicides, herbicides, and rodenticides. Uncontrolled and long-term use of pesticides has become an important issue that causes environmental pollution and health problems. Therefore, it is necessary to develop effective sensors to determine pesticides in various samples. Electrochemical techniques stand out with high sensitivity, easy application, low cost, and user-friendliness, among other analysis techniques such as spectroscopic and chromatographic methods. Furthermore, carbon nanomaterials are advantageous materials for the sensor design as modification agents due to their unique electrical, physical, electrocatalytic, and chemical features. In this review, the most significant studies on the electroanalysis of pesticides (e.g., carbaryl, carbofuran, chlorpyrifos, malathion, methyl parathion, paraoxon) using carbon-based nanosensors in the last five years are overviewed. In addition, electrochemical methods and the carbon nanomaterials used in these studies are also evaluated.     

A wireless magnetoelastic biosensor for the direct detection of organophosphorus pesticides

An organophosphorus (OP) pesticide sensor was fabricated by applying a pH-sensitive polymer coating and organophosphorus hydrolase (OPH) enzyme onto the surface of a magnetoelastic sensor, the magnetic analogue of the better-known surface acoustic wave sensor. Organophosphorus hydrolase catalyses the hydrolysis of a wide range of organophosphorus compounds, which changes the pH in the hydrogel. This article describes the application of the magnetoelastic sensor for the detection of OP pesticides by measuring the changes in viscoelasticity caused by the swelling/shrinking of the pH-responsive polymer when exposed to the pesticides. The sensor was successfully used to detect paraoxon and parathion down to a concentration of 1 x 10(-7) and 8.5 x 10(-7) M respectively.     

Nanomaterials based non-enzymatic electrochemical and optical sensors for the detection of carbendazim: A review

Carbendazim sensors with high sensitivity and selectivity have become imperative for the welfare of the food industry, agriculture, aquaculture, and forestry. The design and development of sensors with high sensitivity and selectivity require deeper insights into the chemistry of nanomaterials. Driven by these needs, we intend to offer a concise discussion of diverse materials and various analytical techniques employed for carbendazim detection. This review focuses on interpreting the performance of well-recognized techniques integrated with keenly engineered nanomaterials, critical discussions on the drawbacks of the available sensors, and subsequent advances in nano-tailored materials. This review also provides constructive ideas for the requirement of maiden electrochemical and optical sensors, as well as existing challenges and future prospects.     

High-sensitivity nanosensors for biomarker detection

High sensitivity nanosensors utilize optical, mechanical, electrical, and magnetic relaxation properties to push detection limits of biomarkers below previously possible concentrations. The unique properties of nanomaterials and nanotechnology are exploited to design biomarker diagnostics. High-sensitivity recognition is achieved by signal and target amplification along with thorough pre-processing of samples. In this tutorial review, we introduce the type of detection signals read by nanosensors to detect extremely small concentrations of biomarkers and provide distinctive examples of high-sensitivity sensors. The use of such high-sensitivity nanosensors can offer earlier detection of disease than currently available to patients and create significant improvements in clinical outcomes.     

无酶葡萄糖电化学传感器的研究进展

随着各种新型材料的层出不穷及其在葡萄糖电化学传感器方面应用的发展,无酶葡萄糖电化学传感器的研制成为葡萄糖电化学传感器的另一个研究热点.本文综述了近年来无酶葡萄糖电化学传感器的研究进展,重点介绍了电流型无酶葡萄糖传感器所使用的各种电极材料,总结了最近五年各种新型结构材料在该类传感器研制方面的应用,并对无酶葡萄糖电化学传感器发展方向和趋势进行了展望.     

An innovative strategy for direct electrochemical detection of microRNA biomarkers

We report an electrochemical method for direct, reagentless, and label-free detection of microRNA, based on a conjugated copolymer, poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-2-carboxyethyl-1,4-naphthoquinone), acting as hybridization transducer. Hybridization between the oligonucleotide capture probe and a microRNA target of 22 base pairs generates an increase in the redox current (“signal-on”), which is evidenced by square wave voltammetry. Selectivity is good, with little hybridization for non-complementary targets, and the limit of detection reaches 650 fM. It is also evidenced that this sensitivity benefits from the high affinity of DNA for RNA.

Surfactant bilayers for the direct electrochemical detection of affinity interactions

Simple methods of preparing the direct affinity sensors are proposed. Due to the self-consistent introduction of a hydrocarbon chain bound with oligonucleotide pentadecathymidylate (dT(15)) into the hydrophobic region of surfactant bilayer or the adsorption of antibodies on the bilayer surface, the immobilizations of oligonucleotide or antibodies were carried out correspondingly. The responses were detected by impedance spectroscopy. Whereas the specific DNA-coupling caused the decrease of real part of impedance, the antibody-antigen interaction caused the increase of real part. The obtained results give an opportunity for the development of impedimetric affinity sensors for clinical analysis or for the detection of various environmental pollutants.     

Functional graphene-gold nano-composite fabricated electrochemical biosensor for direct and rapid detection of bisphenol A

In this research, the graphene with excellent dispersity is prepared successfully by introducing gold nanoparticle to separate the individual sheets. Various techniques are adopted to characterize the prepared graphene and graphene-gold nanoparticle composite materials. This fabricated new composite material is used as the support material to construct a novel tyrosinase based biosensor for detection of bisphenol A (BPA). The electrochemical performances of the proposed new enzyme biosensor were investigated by differential pulse voltammetry (DPV) method. The proposed biosensor exhibited excellent performance for BPA determination with a wide linear range (2.5 × 10⁻³–3.0 μM), a highly reproducible response (RSD of 2.7%), low interferences and long-term stability. And more importantly, the calculated detection limit of the proposed biosensor was as low as 1 nM. Compared with other detection methods, this graphene-gold nanoparticle composite based tyrosinase biosensor is proved to be a promising and reliable tool for rapid detection of BPA for on-site analysis of emergency BPA related pollution affairs.     

A novel non-enzymatic electrochemical glucose sensor modified with FeOOH nanowire

The recent development in the nanotechnology has paved the way for large number of new materials and devices of desirable properties which have useful functions for electrochemical sensor and biosensor applications. In this paper, a novel enzymeless glucose sensor is developed on the discovery that the FeOOH nanowire in fact possesses an intrinsic enzyme mimetic electrocatalytic activity similar to that found in natural peroxidases. The electrode modified with FeOOH nanowires showed a wide linear range (15 μM–3 mM) and high sensitivity (12.13 μA mM^? 1) for glucose sensing. Other excellent performances such as highly reproducible response, long-term stability, sound mechanical and chemical stability are also observed, and the interferences of ascorbic acid and dopamine can almost be completely avoided. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective glucose sensors.     

A microconductometric biosensor based on lipase extracted from Candida rugosa for direct and rapid detection of organophosphate pesticides

Organophosphate pesticides (OPs) have been intensively used as insecticides in agriculture; after entering the aquatic environment, they may affect a wide range of organisms. A conductometric enzymatic biosensor based on lipase extracted from Candida rugosa (CRL) has therefore been developed for the direct and rapid quantitative detection of organophosphate pesticides: diazinon, methyl parathion and methyl paraoxon in water. The biosensor signal and response time were obtained under optimum conditions, the enzyme being immobilised in the presence of gold nanoparticles. Under these conditions, the enzymatic biosensor was able to measure concentrations as low as 60 µg/L of diazinon, 26 µg/L of methyl parathion and 25 µg/L of methyl paraoxon very rapidly (response time: 3 min). Moreover, this CRL biosensor was not sensitive to interferences such as carbamates. It presented good storage stability for 21 days when kept at 4°C and it was successfully applied to real samples.     

Self-organized fluorescent nanosensors for ratiometric Pb2+ detection

Silica nanoparticles (60 nm diameter) doped with fluorescent dyes and functionalized on the surface with thiol groups have been proved to be efficient fluorescent chemosensors for Pb2+ ions. The particles can detect a 1 microM metal ion concentration with a good selectivity, suffering only interference from Cu2+ ions. Analyte binding sites are provided by the simple grafting of the thiol groups on the nanoparticles. Once bound to the particles surface, the Pb2+ ions quench the emission of the reporting dyes embedded. Sensor performances can be improved by taking advantage of the ease of production of multishell silica particles. On one hand, signaling units can be concentrated in the external shells, allowing a closer interaction with the surface-bound analyte. On the other, a second dye can be buried in the particle core, far enough from the surface to be unaffected by the Pb2+ ions, thus producing a reference signal. In this way, a ratiometric system is easily prepared by simple self-organization of the particle components.     

Graphene-based nanocomposites as sensing elements for the electrochemical detection of pesticides: a review

Journal of Solid State Electrochemistry - Only about 3% of Earth’s water is freshwater out of which only 0.4% is accessible as surface water in the form of lakes, rivers and groundwater. When...     

A novel protocol for ultra-trace detection of pesticides: Combined electrochemical reduction of Ellman's reagent with acetylcholinesterase inhibition

This paper proposed a novel method for ultra-trace detection of pesticides combining electrochemical reduction of Ellman's reagent with acetylcholinesterase (AChE) inhibition. The amperometric biosensor, fabricated by immobilizing AChE on multi-walled carbon nanotubes-chitosan (MWCNTs-Chi) nanocomposites modified glassy carbon electrode, enjoyed high sensitivity owing to the excellent conductivity and favourable biocompatibility of MWCNTs-Chi nanocomposites. Meanwhile, the sensitivity of the biosensor was further enhanced using the electrochemical reduction signal of DTNB for determination. Under optimum conditions, methyl parathion was detected based on its inhibition effect on AChE activity and the subsequent change in electrochemical reduction response of DTNB. Good relationship was obtained between the reduction current and pesticide concentration in the ranges of 5.0 × 10⁻⁷ to 1.0 × 10⁻¹² M with a detection limit of 7.5 × 10⁻¹³ M (S/N = 3). Moreover, the proposed protocol was successfully employed for the determination of methyl parathion in water and soil samples.     

A direct Capillary Liquid Chromatography with electrochemical detection method for determination of phenols in water samples

A fast and direct method based on the use of Capillary Liquid Chromatography (LC) with electrochemical (EC) detection has been described for phenols pollutants in water samples. Concretely, phenol, o-cresol, 2-chlorophenol and bisphenol A have been selected as target analytes. The combination of Capillary LC with EC detection avoided the necessity of preconcentration steps typically used in environmental analysis. The sample injected volume was 2μL. The achieved detection limits were between 1 and 2μg/L and the linear dynamic range was up to 50μg/L for all studied phenols. The precision and uncertainty were satisfactory. The analysis time per sample was 10min. The proposed procedure has been proved useful for treated waters.     

A simple non-enzymatic strategy for adenosine triphosphate electrochemical aptasensor using silver nanoparticle-decorated graphene oxide

In this work, a sensitive electrochemical aptasensor for the detection of adenosine triphosphate (ATP) has been introduced. A simple and non-enzymatic signal amplification strategy is utilized using silver nanoparticle-decorated graphene oxide (AgNPs–GO) as a redox probe. The modified electrode surface was characterized by scanning electron microscopy, FTIR and UV–Vis spectroscopy, and electrochemical impedance spectroscopy. GO provides an excellent substrate for the presence of the large number of AgNPs, so the monitored oxidation signal of AgNPs has been amplified. ATP-specific DNA aptamer is split into two fragments (F₁ & F₂) in order to design a sandwich-type assay. For the construction of the sensor, the surface of a graphite screen-printed electrode is modified with electrodeposited gold nanoparticles followed by self-assembling a monolayer of 3-mercaptopropionic acid on the electrode surface. The first amino-labeled fragment, F₁, is immobilized on the modified electrode via carbodiimide chemistry. The synthesized AgNPs–GO interacts with F₁ via \(\pi{-}\pi\) stacking. In the presence of ATP, the second fragment of the aptamer, F₂, forms an associated complex with the immobilized F₁ and causes AgNPs–GO to leave the surface. Consequently, a remarkable decrease in the oxidation signal of the AgNPs is observed. The percentage of this decrease has been monitored as an analytical signal, which is proportional to ATP concentration, and delivers a linear response over the range of 10.0 (±0.6) to 850 (±5) nM with a detection limit of 5.0 (±0.2) nM.     

Determination of triazine pesticides by high-performance liquid chromatography with swept-potential electrochemical detection

A swept-potential electrochemical detector, operating in the square-wave voltammetric mode, is used to detect a mixture of five triazine pesticides separated on a reverse-phase resin column. Limits of detection are below 1 ng injected. Two compounds, not completely separated by the column, are resolved on the potential axis.     

Nanoparticle-based optical biosensors for the direct detection of organophosphate chemical warfare agents and pesticides

Neurotoxic organophosphates (OP) have found widespread use in the environment for insect control. In addition, there is the increasing threat of use of OP based chemical warfare agents in both ground based warfare and terrorist attacks. Together, these trends necessitate the development of simple and specific methods for discriminative detection of ultra low quantities of OP neurotoxins. In our previous investigations a new biosensor for the direct detection of organophosphorus neurotoxins was pioneered. In this system, the enzymatic hydrolysis of OP neurotoxins by organophosphate hydrolase (OPH) generated two protons in each hydrolytic turnover through reactions in which P-X bonds are cleaved. The sensitivity of this biosensor was limited due to the potentiometric method of detection. Recently, it was reported that a change in fluorescence properties of a fluorophore in the vicinity of gold nanoparticles might be used for detection of nanomolar concentrations of DNA oligonucleotides. The detection strategy was based on the fact that an enhancement or quenching of fluorescence intensity is a function of the distances between the gold nanoparticle and fluorophore. While these reports have demonstrated the use of nanoparticle-based sensors for the detection of target DNA, we observed that the specificity of enzyme-substrate interactions could be exploited in similar systems. To test the feasibility of this approach, OPH-gold nanoparticle conjugates were prepared, then incubated with a fluorescent enzyme inhibitor or decoy. The fluorescence intensity of the decoy was sensitive to the proximity of the gold nanoparticle, and thus could be used to indicate that the decoy was bound to the OPH. Then different paraoxon concentrations were introduced to the OPH-nanoparticle-conjugate-decoy mixtures, and normalized ratio of fluorescence intensities were measured. The greatest sensitivity to paraoxon was obtained when decoys and OPH-gold nanoparticle conjugates were present at near equimolar levels. The change in fluorescence intensity was correlated with concentration of paraoxon presented in the solution.     

Functionalization of single-walled carbon nanotubes for direct and selective electrochemical detection of DNA

We report here a new strategy to graft both redox and DNA probes on carbon nanotubes to make a label-free DNA sensor. Oxidized single-walled carbon nanotubes are first immobilized on a self-assembled monolayer of cysteamine; then the redox probe, a quinone derivative 3-[(2-aminoethyl)sulfanyl-5-hydroxy-1,4-naphthoquinone], is grafted on the free carboxylic groups of the nanotubes. After that, for DNA probe grafting, new carboxylic sites are generated via an aryl diazonium route. After hybridization with a complementary sequence, the conformational changes of DNA could influence the redox kinetics of quinone, leading to a current increase of the redox signal, detected by square wave voltammetry. The system is selective, as it can discriminate a single mismatched sequence from the complementary one.     

Innovative approach for the electrochemical detection of non-electroactive organophosphorus pesticides using oxime as electroactive probe

An innovative approach for sensitive and simple electrochemical detection of non-electroactive organophosphorus pesticides (OPs) was described in this report. The novel strategy emphasized the fabrication of an oxime-based sensor via attaching pralidoxime (PAM) on graphene quantum dots (GQDs) modified glassy carbon electrode. The introduction of GQDs significantly increased the effective electrode area, and then enlarged the immobilization quantity of PAM. Thus, the oxidation current of PAM was obviously increased. Relying on the nucleophilic substitution reaction between oxime and OPs, fenthion was detected using PAM as the electroactive probe. Under optimum conditions, the difference of oxidation current of PAM was proportional to fenthion concentration over the range from 1.0 × 10⁻¹¹ M to 5.0 × 10⁻⁷ M with a detection limit of 6.8 × 10⁻¹² M (S/N = 3). Moreover, the favorable detection performance in water and soil samples heralded the promising applications in on-site OPs detection.