Xiangyou Wang

Acetylcholinesterase biosensor based on chitosan/prussian blue/multiwall carbon nanotubes/hollow gold nanospheres nanocomposite film by one-stepelectrodeposition

In this paper, chitosan-prussian blue-multiwall carbon nanotubes-hollow gold nanospheres (Chit-PB-MWNTs-HGNs) film was fabricated onto the gold electrode surface by one-step electrodeposition method; and then acetylcholinesterase (AChE) and Nafion were modified onto the film to prepare an AChE biosensor. Incorporating MWNTs and HGNs into Chit-PB hybrid film promoted electron transfer reaction, enhanced the electrochemical response and improved the microarchitecture of the electrode surface. The morphologies and electrochemistry properties of the composite were investigated by using scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy, respectively. Parameters affecting the biosensor response such as pH, enzyme loading and inhibition time were optimized. Based on the inhibition of pesticides on the AChE activity, using malathion, chlorpyrifos, monocrotophos and carbofuran as model compounds, this biosensor showed a wide range, low detection limit, good reproducibility and high stability. Moreover, AChE/Chit-PB-MWNTs-HGNs/Au biosensor can also be used for direct analysis of practical samples, which would be a new promising tool for pesticide analysis.

A Label-Free Electrochemical Immunosensor for Carbofuran Detection Based on a Sol-Gel Entrapped Antibody

In this study, an anti-carbofuran monoclonal antibody (Ab) was immobilized on the surface of a glassy carbon electrode (GCE) using silica sol-gel (SiSG) technology. Thus, a sensitive, label-free electrochemical immunosensor for the direct determination of carbofuran was developed. The electrochemical performance of immunoreaction of antigen with the anti-carbofuran monoclonal antibody was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), in which phosphate buffer solution containing [Fe(CN)6]3−/4− was used as the base solution for test. Because the complex formed by the immunoreaction hindered the diffusion of [Fe(CN)6]3−/4− on the electrode surface, the redox peak current of the immunosensor in the CV obviously decreased with the increase of the carbofuran concentration. The pH of working solution, the concentration of Ab and the incubation time of carbofuran were studied to ensure the sensitivity and conductivity of the immunosensor. Under the optimal conditions, the linear range of the proposed immunosensor for the determination of carbofuran was from 1 ng/mL to 100 μg/mL and from 50 μg/mL to 200 μg/mL with a detection limit of 0.33 ng/mL (S/N = 3). The proposed immunosensor exhibited good high sensitivity and stability, and it was thus suitable for trace detection of carbofuran pesticide residues.

Lanthanum- and cerium-induced oxidative stress in submerged Hydrilla verticillata plants

Oxidative stress was induced in 10-day treated with lanthanum and cerium Hydrilla verticillata plants. Low 10 μM concentrations did not exert harmful effects. The plants treated with higher concentrations showed higher H2O2 content and lower chlorophyll and soluble protein contents as compared to control plants. At the same time, malondialdehyde content rose with increasing concentrations of La and Ce. As La and Ce concentrations increased, superoxide dismutase and catalase activities declined progressively, while peroxidase activity increased. Proline content decreased slightly at 10 μM La or Ce and then rose with higher concentrations. The results indicated that La and Ce caused oxidative damage as evidenced by increased lipid peroxidation and decreased chlorophyll and protein levels.

An Amperometric Immunosensor Based on Multi-Walled Carbon Nanotubes-Thionine-Chitosan Nanocomposite Film for Chlorpyrifos Detection

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.

An acetylcholinesterase biosensor based on graphene-gold nanocomposite and calcined layered double hydroxide.

In this study, a novel acetylcholinesterase-based biosensor was fabricated. Acetylcholinesterase (AChE) was immobilized onto a glassy carbon electrode (GCE) with the aid of Cu-Mg-Al calcined layered double hydroxide (CLDH). CLDH can provide a bigger effective surface area for AChE loading, which could improve the precision and stability of AChE biosensor. However, the poor electroconductibility of CLDHs could lead to the low sensitivity of AChE biosensor. In order to effectively compensate the disadvantages of CLDHs, graphene-gold nanocomposites were used for improving the electron transfer rate. Thus, the graphene-gold nanocomposite (GN-AuNPs) was firstly modified onto the GCE, and then the prepared CLDH-AChE composite was immobilized onto the modified GCE to construct a sensitive AChE biosensor for pesticides detection. Relevant parameters were studied in detail and optimized, including the pH of the acetylthiocholine chloride (ATCl) solution, the amount of AChE immobilized on the biosensor and the inhibition time governing the analytical performance of the biosensor. The biosensor detected chlorpyrifos at concentrations ranging from 0.05 to 150μg/L. The detection limit for chlorpyrifos was 0.05μg/L.

Electrochemical Aptasensor Based on Prussian Blue-Chitosan-Glutaraldehyde for the Sensitive Determination of Tetracycline

In this paper, a novel and sensitive electrochemical aptasensor for detecting tetracycline (TET) with prussian blue (PB) as the label-free signal was fabricated. A PB-chitosan-glutaraldehyde (PB-CS-GA) system acting as the signal indicator was developed to improve the sensitivity of the electrochemical aptasensor. Firstly, the PB-CS-GA was fixed onto the glass carbon electrode surface. Then, colloidal gold nanoparticles (AuNPs) were droped onto the electrode to immobilize the anti-TET aptamer for preparation of the aptasensor. The stepwise assembly process of the aptasensor was characterized by cyclic voltammetry (C-V) and scanning electron microscope (SEM). The target TET captured onto the electrode induced the current response of the electrode due to the non-conducting biomoleculars. Under the optimum operating conditions, the response of differential pulse voltammetry (DPV) was used for detecting the concentration of TET. The proposed aptasensor showed a high sensitivity and a wide linear range of 10−9 ∼ 10−5 M and 10−5 ∼ 10−2 M with the correlation coefficients of 0.994 and 0.992, respectively. The detection limit was 3.2×10−10 M (RSD 4.12%). Due to its rapidity, sensitivity and low cost, the proposed aptasensor could be used as a pre-scanning method in TET determination for the analysis of livestock products.

Acetylcholinesterase biosensor based on the mesoporous carbon/ferroferric oxide modified electrode for detecting organophosphorus pesticides

In this paper a biosensor modified by ordered mesoporous carbon–chitosan (OMC–CS)/ferroferric oxide–chitosan (Fe3O4–CS) was developed on the surface of screen-printed carbon electrodes (SPCEs). The acetylcholinesterase (AChE) was modified onto the film to prepare an AChE biosensor. Chitosan was used as a dispersant to disperse OMC and Fe3O4. The OMC and Fe3O4 were used to enhance the electrochemical response. Before the detection of organophosphorus (OP) pesticides, the electrochemical behaviour of AChE/OMC–CS/Fe3O4–CS/SPCE was studied with cyclic voltammetry, and the results showed that the chitosan can disperse OMC and Fe3O4 evenly and fix them on the electrode surface firmly. OMC and Fe3O4 have a significant synergistic effect towards electron transfer. The parameters affecting performance, such as the pH of the test solution, the amount of AChE and the time of inhibition have been optimized. Under optimum conditions, using methamidophos and chlorpyrifos as model compounds, this biosensor showed a wide range, low detection limit, good reproducibility and high stability. Moreover, the AChE/OMC–CS/Fe3O4–CS/SPCE biosensor can be used for the detection of real samples, and is suitable for field testing of OP pesticide residues.

Acetylcholinesterase Biosensor Based on Poly (diallyldimethylammonium chloride)-multi-walled Carbon Nanotubes-graphene Hybrid Film

In this paper, an amperometric acetylcholinesterase (AChE) biosensor for quantitative determination of carbaryl was developed. Firstly, the poly (diallyldimethy-lammonium chloride) -multi-walled carbon nanotubes-graphene hybrid film was modified onto the glassy carbon electrode (GCE) surface, then AChE was immobilized onto the modified GCE to fabricate the AChE biosensor. The morphologies and electrochemistry properties of the prepared AChE biosensor were investigated by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. All variables involved in the preparation process and analytical performance of the biosensor were optimized. Based on the inhibition of pesticides on the AChE activity, using carbaryl as model compounds, the biosensor exhibited low detection limit, good reproducibility and high stability in a wide range. Moreover, the biosensor can also be used for direct analysis of practical samples, which would provide a new promising tool for pesticide residues analysis.

Amperometric Acetylcholinesterase Biosensor Based on O-Carboxymethyl Chitosan-Gold Nanoparticle Nanocomposite by In-Situ Synthesis Method

The nanocomposite comprised of O-carboxymethyl chitosan (CMCS) and gold nanoparticles (AuNPs) is successfully prepared by in-situ synthesis method. The synthesized nanocomposite has been characterized by scanning electron microscopy images. The CMCS-AuNPs nanocomposite is first modified onto the glassy carbon electrode (GCE), then the surface carboxyl group is activated by N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. Finally, the acetylcholinesterase (AChE) is immobilized onto the GCE to construct a novel AChE biosensor for the detection of pesticides. Because the nanocomposite was able to inherit the properties of the AuNPs and CMCS, the resulting surface provided a favorable microenvironment for AChE biosensor fabrication and maintained the bioactivity of AChE for screening of pesticide exposure. Based on the inhibition of pesticides on AChE activity using chlorpyrifos as the model compound, the results showed that the inhibition of chlorpyrifos is proportional to its concentration ranging from 0.1 to 20 μg/L and 20 to 100 μg/L, with a detection limit of 0.07 μg/L (S/N=3). The developed biosensor exhibited good reproducibility, acceptable stability, fast response, and low detection limit, thus providing a new promising tool for the rapid detection of pesticides.

Acetylcholinesterase biosensor for carbaryl detection based on interdigitated array microelectrodes

In this study, an acetylcholinesterase (AChE) biosensor with superior accuracy and sensitivity was successfully developed based on interdigitated array microelectrodes (IAMs). IAMs have a series of parallel microband electrodes with alternating microbands connected together. Chitosan was used as the enzyme immobilization material, and AChE was used as the model enzyme for carbaryl detection to fabricate AChE biosensor. Electrochemical impedance spectroscopy was used in conjunction with the fabricated biosensor to detect pesticide residues. Based on the inhibition of pesticides on the AChE activity, using carbaryl as model compounds, the biosensor exhibited a wide range, low detection limit, and high stability. Moreover, the biosensor can also be used as a new promising tool for pesticide residue analysis.