Amperometric Biosensor Based on Immobilization Acetylcholinesterase on Manganese Porphyrin Nanoparticles for Detection of Trichlorfon with Flow‐Injection Analysis System

A highly sensitive amperometric biosensor for the detection of organophosphate pesticides (OPs) is developed. The biosensor was fabricated by immobilized acetylcholinesterase (AChE) on manganese (III) meso‐tetraphenylporphyrin (MnTPP) nanoparticles (NPs)‐modified glassy carbon (GC) electrode. The MnTPP NPs used in this article were synthesized by mixing solvent techniques. AChE enzyme was immobilized on the MnTPP NPs surface by conjugated with chitosan (CHIT). The electrocatalytic activity of MnTPP NPs led to a greatly improved performance for thiocholine (TCh) product detection. The developed AChE‐CHIT/MnTPPNP/GC biosensor integrated with a flow‐injection analysis (FIA) system was used to monitor trichlorfon (typical OP). A wide linear inhibition response for trichlorfon is observed in the range of 1.0 nM–1.0 mM, corresponding to 10–83% inhibition for AChE with a detection limit of 0.5 nM.     

Au掺杂Fe3O4纳米粒子酶传感器的制备及其应用于有机磷农药检测的研究

合成了金掺杂的四氧化三铁纳米粒子(Au-Fe₃O₄), 以壳聚糖为交联剂, 制备了电流型乙酰胆碱酯酶(AChE)生物传感器, 并将其应用于有机磷农药(OPs)的检测. 实验表明, Au-Fe₃O₄纳米粒子具有良好的生物兼容性, 能够有效地促进电子传递, 修饰了Au-Fe₃O₄纳米粒子的酶传感器, 响应速度快, 检测灵敏度高, 稳定性好; 固定在传感器上的乙酰胆碱酯酶有良好的酶动力学响应, 其表观米氏常数( )为10.3 mmol/L. 利用有机磷农药对乙酰胆碱酯酶的抑制作用, 以硫代乙酰胆碱(ATCh)为底物, 对有机磷农药敌敌畏进行了检测, 检测限达到4.0×10^－13 mol/L.     

An amperometric biosensor based on acetylcholinesterase immobilized onto iron oxide nanoparticles/multi-walled carbon nanotubes modified gold electrode for measurement of organophosphorus insecticides

An acetylcholinesterase (AChE) purified from maize seedlings was immobilized covalently onto iron oxide nanoparticles (Fe₃O₄NP) and carboxylated multi walled carbon nanotubes (c-MWCNT) modified Au electrode. An organophosphorus (OP) biosensor was fabricated using this AChE/Fe₃O₄/c-MWCNT/Au electrode as a working electrode, Ag/AgCl as standard and Pt wire as an auxiliary electrode connected through a potentiostat. The biosensor was based on inhibition of AChE by OP compounds/insecticides. The properties of nanoparticles modified electrodes were studied by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS). The synergistic action of Fe₃O₄NP and c-MWCNT showed excellent electrocatalytic activity at low potential (+0.4 V). The optimum working conditions for the sensor were pH 7.5, 35 °C, 600 μM substrate concentration and 10 min for inhibition by pesticide. Under optimum conditions, the inhibition rates of OP pesticides were proportional to their concentrations in the range of 0.1–40 nM, 0.1–50 nM, 1–50 nM and 10–100 nM for malathion, chlorpyrifos, monocrotophos and endosulfan respectively. The detection limits were 0.1 nM for malathion and chlorpyrifos, 1 nM for monocrotophos and 10 nM for endosulfan. The biosensor exhibited good sensitivity (0.475 mA μM⁻¹), reusability (more than 50 times) and stability (2 months). The sensor was suitable for trace detection of OP pesticide residues in milk and water.     

A rational design of the multiwalled carbon nanotube–7,7,8,8-tetracyanoquinodimethan sensor for sensitive detection of acetylcholinesterase inhibitors

A new, simple and effective amperometric acetylcholinesterase biosensor was developed using screen-printed carbon electrodes modified with carbon nanotubes (MWCNTs)–7,7,8,8-tetracyanoquinodimethane (TCNQ). The design of the biosensor was based on the supramolecular arrangement resulted from the interaction of MWCNTs and TCNQ. This arrangement was confirmed by spectroscopic and electrochemical techniques. Two different supramolecular arrangements were proposed based on different MWCNTs:TCNQ ratios. The synergistic effect of MWCNTs and TCNQ was, for the first time, exploited for detection of thiocholine at low potential with high sensitivity. The biosensor developed by immobilization of acetylcholinesterase (AChE) in sol–gel allowed the detection of two reference AChE inhibitors, paraoxon-methyl and chlorpyrifos with detection limits of 30 pM (7 ppt) and 0.4 nM (0.1 ppb), respectively. Efficient enzyme reactivation was obtained by using obidoxime.     

Critical evaluation of electrode design and matrix effects on monitoring organophosphate pesticides using composite carbon nanotube-modified electrodes

Carbon nanotubes (CNT)/Nafion-modified glassy carbon (GC) electrodes were used to immobilize the enzyme acetylcholinesterase (AChE) by crosslinking with glutaraldehyde. The CNT-modified electrodes exhibited a sensitive and stable electrocatalytic behavior towards thiocholine (TCh). Compared to ordinary GC electrodes modified with Nafion, a substantial (500-mV) decrease in the overvoltage of the TCh oxidation reaction is observed, along with a tenfold enhancement in the amperometric response. The CNT/Nafion/AChE electrode has very good stability of at least a month compared to surfaces made without crosslinking in the absence and presence of Nafion. Under optimal loadings of CNT, Nafion, AChE, and glutaraldehyde, a solution of CNT/Nafion in N,N-dimethylformamide (DMF) containing 4 mg/mL CNT and 0.01% Nafion was used to construct the electrodes in order to maximize the sensitivity of the biosensor for inhibition studies. An optimal enzyme loading of 0.137 U and crosslinking in 0.01% glutaraldehyde for 1 h was also needed to achieve this goal. The prepared electrodes had very good reproducibility to 1.0 mM acetylthiocholine (ATCh) (relative standard deviation [RSD] <5% for eight electrodes). Using paraoxon as a model pesticide, the biosensor was able to detect as low as 1.0 nM after 30 min of incubation at 30 °C. Using a log scale, the biosensor had good linearity in the concentration range 50?C800 nM, with a correlation coefficient of 0.99. The prepared biosensor was used to test real water samples spiked with paraoxon and showed good correlation with a calibration curve using phosphate buffer.     

Determination of Anticholinesterase Activity for Pesticides Monitoring Using a Thiocholine Sensor

Abstract

An acetylthiocholine sensor based on a disposable screen-printed carbon electrode has been assembled for measuring organophosphorus and carbamate pesticides in river water samples through the degree of inhibition of the enzyme acetylcholinesterase (AChE). The carbon working electrode surface was modified by deposition of a mediator, tetracyanoquinodimethane (TCNQ), and Nafion. Acetylcholinesterase catalyses the cleavage of acetylthiocholine to thiocholine, which is measured by differential pulse voltammetry and directly related to the enzyme activity. The scan speed, the pulse amplitude of the differential pulse voltammetry and several parameters in the procedure were optimised. An inhibition calibration curve was obtained using carbofuran. The method was also applied to water samples, showing its suitability as a rapid screening assay (15 min per test) for anticholinesterase activity detection.     

Ionic liquid-functionalized graphene for fabricating an amperometric acetylcholinesterase biosensor

This work reports a sensitive amperometric biosensor for organophosphate pesticides (OPs) fabricated by modifying a glassy carbon electrode with acetylcholinesterase (AChE) immobilized on ionic liquid-functionalized graphene (IL-G). The functionalized graphene sheets had good dispersibility and long-term stability in various solvents. The as-prepared biosensor showed high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.77 mM. Furthermore, based on the inhibition by OPs of the enzymatic activity of the immobilized AChE, and using carbaryl as a model compound, the inhibition of carbaryl was proportional to its concentration ranging from 0.0025 to 0.48 and 0.48 to 1.42 μg mL(-1) with a detection limit of 0.8 ng mL(-1) (S/N = 3). The developed biosensor exhibited a good performance for OPs detection, including good reproducibility and acceptable stability, which provided a new and promising tool for the analysis of enzyme inhibitors.     

Development of Quantum Dots Modified Acetylcholinesterase Biosensor for the Detection of Trichlorfon

Poly (N‐vinyl‐2‐pyrrolidone) (PVP)‐capped CdS quantum dots (QCdS‐PVP) was synthesized with CdCl₂ and Na₂S in the presence of PVP. QCdS‐PVP has been used for the immobilization and stabilization of the acetylcholinesterase (AChE). The electrocatalytic activity of QCdS‐PVP leads to a greatly improved electrochemical detection of the enzymatically generated thiocholine product, and higher sensitivity and stability. The GCE/QCdS‐PVP/AChE biosensor was used for the detection of organophosphate pesticides (OPs), such as trichlorfon. The sensor performance, including pH and inhibition time, was optimized with respect to operating conditions. Under the optimal conditions, the biosensor was used to measure as low as 12 ppb trichlorfon with a 5‐min inhibition time.     

层层自组装纳米金与乙酰胆碱酯酶电化学生物传感器检测有机磷农药

采用层层自组装技术制备了快速检测有机磷农药的生物传感器,利用带正电荷的高分子聚电解质聚二烯丙基二甲基氯化铵(PDDA)将乙酰胆碱酯酶(AChE)和金纳米粒子(AuNPs)通过静电力逐层固定到玻碳电极(GCE)表面,并采用交流阻抗和微分脉冲伏安法研究了此生物传感器的电化学行为。由于金纳米粒子优异的电催化性能和良好的生物相容性,使固定化的乙酰胆碱酯酶对其底物具有更高的亲和力和更快的响应速度。实验结果表明:修饰金纳米粒子后,传感器的氧化电流明显增大,在4.6×10-5～5.3×10-3mol/L范围内,固定化酶的抑制率与甲基对硫磷浓度的对数成正比,检出限为7.6×10-6mol/L。该生物传感器具有制备方法简便、成本低、灵敏度高等优点,已成功用于蔬菜样品中甲基对硫磷含量的测定。     

Application of Carbon Nanotubes in the Extraction and Electrochemical Detection of Organophosphate Pesticides: A Review

Recent trends and challenges in developing carbon nanotubes (CNT) based sensors and biosensors for the detection of organophosphate (OP) pesticides and other organic pollutants in water are reviewed. CNT have superior electrical, mechanical, chemical, and structural properties over conventional materials such as graphite. At the same time CNT based sensors and biosensors are more efficient compared to the existing traditional techniques such as high-performance liquid chromatography or gas chromatography, because they can provide rapid, sensitive, simple, and low-cost on-field detection. The measurement protocols can be based on enzymatic and non-enzymatic detection. The enzyme acetylcholinesterase (AChE) is used with CNT for fabricating ultrasensitive biosensors for OP detection involving different immobilization schemes such as adsorption, crosslinking, and layer-by-layer self-assembly. This protocol relies on measuring the degree of enzyme inhibition as means of OP quantification. The other enzyme used along with CNT for OP detection is organophosphate hydrolase (OPH) which hydrolyzes the OP into detectable species that can be measured by amperometric or potentiometric methods. Different forms of CNT electrode materials can be used for fabricating such electrodes such as pure CNT and composite CNT. Due to their large surface area and hydrophobicity, CNT have also been used for the extraction and non-enzymatic electrochemical detection of OP with very high efficiency. The application of CNT and their novel properties for the adsorption and electrochemical detection of OP compounds is discussed in detail.     

Nerve Agents Assay Using Cholinesterase Based Biosensor

Electrochemical biosensor based on electric eel acetylcholinesterase (AChE) (EC 3.1.1.7) was performed for assay of nerve agents – tabun, sarin, soman, cyclosarin, and VX. The biosensor used AChE as biorecognition element. The presence of nerve agents was accompanied by a strong inhibition of AChE activity. Enzyme activity is easily measurable by electrochemical oxidation of thiocholine created from acetylthiocholine (ATChCl) by AChE‐catalyzed hydrolysis. The tested nerve agents were successfully assayed. The best limits of detection were achieved for sarin (5.88×10^?10 M) and VX (8.51×10^?10 M) after one‐minute assay. The biosensor was found long term stable at low as well as laboratory temperature.     

A hydrogen peroxide biosensor with high stability based on gelatin-multiwalled carbon nanotubes modified glassy carbon electrode

A biosensor with high stability was prepared to determine hydrogen peroxide (H₂O₂). This hydrogen peroxide biosensor was obtained by modifying glassy carbon electrode (GCE) with a composite film composed of gelatin-multiwalled carbon nanotubes. Catalase (Cat) was covalently immobilized into gelatin-multiwalled carbon nanotubes modified GCE through the well-known glutaraldehyde (GAD) chemistry in order to enhance the stability of electrodes. The enzyme sensor can achieve direct electrochemical response of hydrogen peroxide. The cyclic voltammograms at different scan rates, electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) tests indicate that the enzyme sensor performs positively on increasing permeability, reducing the electron transfer resistance, and improving the electrode performance. The linear response of standard curve for H₂O₂ is in the range of 0.2 to 5.0 mM with a correlation coefficient of 0.9972, and the detection limit of 0.001 mM. A high operational and storage stability is demonstrated for the biosensor. The peak potential at room temperature in two consecutive weeks stays almost consistent, and the enzyme activity is kept stable even after 30 days in further study.     

A mediator-free screen-printed amperometric biosensor for screening of organophosphorus pesticides with flow-injection analysis (FIA) system

A mediator-free amperometric biosensor for screening organophosphorus pesticides (OPs) in flow-injection analysis (FIA) system based on anticholinesterase activity of OPs to immobilized acetylcholinesterase enzyme (AChE) has been developed. The enzyme biosensor is prepared by entrapping AChE in Al₂O₃ sol-gel matrix screen-printed on an integrated 3-electrode plastic chip. This strategy is found not only increase the stability of the embedded AChE, but also effectively catalyze the oxidative reaction of thiocholine, making the Al₂O₃-AChE biosensor detects the substrate at 0.25 V (versus Ag/AgCl), hundreds mini-volt lower than other reported mediator-free ones. The Al₂O₃-AChE biosensor is thus coupled to FIA system to build up a simple and low-cost FIA-EC system for screening OPs in real samples. A wide linear inhibition response for dichlorvos, typical OP, is observed in the range of 0.1-80 μM, corresponding to 7.91-84.94% inhibition for AChE. The detection limit for dichlorvos is achieved at 10 nM in the simulated seawater for 15 min inhibiting time, which allows the biosensor quantitatively detects the ecotoxicological effect of the real samples from the seaports in eastern China, where the OPs pollution is confirmed by GC-MS.     

Diazirine‐functionalized Nanostructured Platform for Enzymes Photografting and Electrochemical Biosensing

A simple technique for the construction of a versatile diazirine‐functionalized nanostructured platform for enzymes photografting and electrochemical biosensing was proposed in this work. The feasibility of the approach was proved by photo crosslinking of an enzyme, tyrosinase, to diazirine‐activated aminated carbon nanotubes coated glassy carbon electrode. The analytical performances of the realized biosensor were evaluated employing catechol as analyte. Then the sensor based on the diazirine‐functionalized nanostructured platform with photografted tyrosinase was applied together with the high resolution technique Differential Alternative Pulses Voltammetry for dopamine determination in the linear concentration range of 5–25 μmol L^?1 in the presence of interfering agents as uric acid up to its 100‐fold excess.     

Determination of Total Monoamines in Rat Brain via Nanotubes Based Human Monoamine Oxidase B Biosensor

A specific and sensitive electrochemical biosensor with human monoamine oxidase B (hMAO B) as biological receptor and a MnO₂ modified nanomaterial based transducer system has been developed and optimised. Best results for the biosensor were achieved when using enzyme immobilisation with a dialysis membrane (regenerated cellulose, molecular weight cut‐off 14000) and a 20 % (m/m) MnO₂ modified multi‐walled carbon nanotubes (MWCNTs, ratio of fluid to solid compounds of 1 : 0.7 (m/m)) paste electrode smoothed with a glassy carbon paste (GCP, ratio 1 : 3.6 (m/m)) containing the same mediator concentration. The biosensor was operated in a flow injection analysis (FIA) system with Sørensen phosphate buffer (33 mM, pH 7.5) and amperometric detection at a fixed potential of +400 mV vs. Ag/AgCl. The developed sensor underwent validation using phenylethylamine (PEA) as standard substrate showing linearity between 5.0 and 400 µM PEA and limits of detection and quantification of 1.5 and 5.0 µM PEA, respectively. The sensor was successfully tested for the determination of total monoamines in rat brain calculated as PEA equivalents showing a result of 1.2 µg/g brain tissue (n=3, relative standard deviation 4.4 %).     

An electrochemical sensor for pesticide assays based on carbon nanotube-enhanced acetycholinesterase activity

There has been urgent demand for rapid, sensitive and cost-effective pesticide assay technologies due to the global attention of environmental and food-safety problems. Acetycholinesterase (AChE)-based electrochemical sensors have attracted significant interest toward this goal. In this contribution, we introduced multiwalled carbon nanotubes (MWNTs) into our sensor design, where they played dual enhancement roles; first is that MWNTs loaded on glassy carbon (GC) electrodes significantly increase surface areas, facilitating the electrochemical polymerization of prussian blue (PB), a redox mediator for the electrochemical oxidation of the enzymatic product, thiocholine (TCh). Second, MWNTs enhance the enzymatic activity of AChE, as manifested by the decreased Michaelis-Menten constant (K(m)). As a result of these two important enhancement factors offered by MWNTs, our electrochemical pesticide sensor exhibited rapid response and high sensitivity toward the detection of a series of pesticides. Moreover, we demonstrated that this sensor was stable, reproducible and selective enough for detection in real samples.     

Acetylcholinesterase Sensor Based on Polyelectrolyte Complexes with DNA Inclusion for the Determination of Reversible Inhibitors

The acetylcholinesterase (AChE) biosensor has been developed for the determination of reversible inhibitors applied in the Alzheimer's disease therapy, i. e., Huperzine A (HupA) and galantamine (Gal). For this purpose, glassy carbon electrode (GCE) was first modified with carbon black (CB) and Co phthalocyanine and then polyelectrolyte complex was self‐assembled on its surface by drop casting of reactants and washing. To extend the stability and improve biosensor performance, it was proposed for the first time to use DNA as polyanion in the complex assembly. The DNA showed higher charge density than conventional polyelectrolytes and stabilized the surface coating by adsorption of higher enzyme amount and prevention of its leaching during the biosensor operation. Complex formation and the influence of structural factors were monitored with surface plasmon resonance. Kinetic study showed mixed inhibition of the enzyme within micro‐ and nanomolar range of inhibitor concentrations. The AChE biosensor showed limit of detection of HupA equal to 0.9 and that of Gal to 70 nM. The sensitivity of drug determination was found to be close or better than that of the AChE biosensors previously reported in the literature. The biosensor was tested on the sample of artificial urine and showed 102 % recovery of the drugs determination.     

基于功能化石墨烯-聚乙烯醇复合膜固定乙酰胆碱酯酶的甲拌磷传感器

将功能化离子液体修饰石墨烯(IL-GR)分散在聚乙烯醇(PVA)中,制得IL-GR-PVA分散液,与乙酰胆碱酯酶(ACh E)溶液混匀后滴涂在电极表面,利用PVA良好的成膜特性,制得新型有机磷检测酶电极ACh E/IL-GR-PVA/GCE,并用于有机磷农药的检测。采用透射电镜(TEM)表征了IL-GR的形貌,采用循环伏安法(CV)和差示脉冲伏安法(DPV)研究了酶电极的电化学性质。结果表明,IL-GR-PVA复合膜具有良好的导电性和生物相容性,能很好地保持ACh E的生物活性,并显著促进了其电化学过程。在优化实验条件下,抑制率(I%)与甲拌磷浓度的负对数在1.0×10-14~1.0×10-9mol/L和1.0×10-9~1.0×10-6mol/L范围内呈良好的线性关系,检出限(S/N=3)为8.0×10-15mol/L。该传感器制备简单,稳定性好,灵敏度高,为有机磷农药的测定提供了新方法。     

Study of enzyme biosensor based on carbon nanotubes modified electrode for detection of pesticides residue

The paper describes a controllable layer-by-layer （LBL） self-assembly modification technique of multi-walled carbon nanotubes （MWNTs） and poly（diallyldimethylammonium chloride） （PDDA） towards glassy carbon electrode （GCE）, Acetylcholinesterase （ACHE） was immobilized directly to the modified GCE by LBL self-assembly method, the activity value of AChE was detected by using i-t technique based on the modified Ellman method. Then the composition of carbaryl were detected by the enzyme electrode with 0.01U activity value and the detection limit of carbaryl is 10^- 12 g L ^-1 so the enzyme biosensor showed good properties for pesticides residue detection.     

Pulsed Deposited Manganese and Vanadium Oxide Film Modified with Carbon Nanotube and Gold Nanoparticle: Chitosan and Ionic Liquid‐based Biosensor

Present study describes the synthesis of mixed oxide films of manganese and vanadium by electrochemical pulsed deposition technique on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT). The film was further decorated with gold nanoparticles to enhance the reduction signal of dissolved oxygen in pH 5.17 acetate buffer solution. All of the electrochemical synthesized modified electrodes have been characterized with Scanning electron microscopy(SEM), High‐resolution transmission electron microscopy (HRTEM), X‐Ray photoelectron spectroscopy (XPS), X‐Ray diffraction (XRD) techniques. The electrode obtained (AuNPs/MnOx?VOx/CNT/GCE) was utilized as a platform for glucose biosensor where the glucose oxidase enzyme was immobilized on the composite film with the aid of chitosan and an ionic liquid. The electrochemical performance of the biosensor was investigated by cyclic voltammetry and the relative parameters have been optimized by amperometric measurements in pH 5.17 acetate buffer solution. The developed biosensor exhibited a linear range for glucose between 0.1–1.0 mM and the limit of detection was calculated as 0.02 mM.