Shuyuan Du

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.

Amperometric Immunosensor Based on L-Cysteine/Gold Colloidal Nanoparticles for Carbofuran Detection

In this study, anti-carbofuran monoclonal antibodies (Ab) were immobilized onto a gold electrode surface modified with multilayers of L-cysteine and gold colloidal nanoparticles (GNPs). Furthermore, horseradish peroxidase (HRP) as enzyme membrane was used for blocking unspecific sites and amplifying signal. The conformational properties of the immunosensor were characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The concentration of antibody solution, pH of working buffer and incubation time were studied in detail for optimization of analytical performance. Under optimal conditions, the variation of current response was proportional to the concentration of carbofuran which ranged from 0.01 ng/mL to 50 ng/mL with a correlation coefficient of 0.9912. The detection limit was 0.01 ng/mL (S/N = 3). The proposed immunosensor exhibited good reproducibility and stability and it can be used for the rapid detection of carbofuran pesticide.

Amperometric Immunosensor Based on Gold Nanoparticles/Fe3O4-FCNTs-CS Composite Film Functionalized Interface for Carbofuran Detection

In this paper, a novel amperometric immunosensor for the determination of carbofuran based on gold nanoparticles (GNPs), magnetic Fe3O4 nanoparticles-functionalized multiwalled carbon nanotubes-chitosan (Fe3O4-FCNTs-CS), and bovine serum albumin (BSA) composite film was proposed. First, GNPs were immobilized onto the glassy carbon electrode (GCE) surface, and then the magnetic Fe3O4 nanoparticles mixed with chitosan-functionalized multiwall carbon nanotubes (CS-FCNTs) homogeneous composite (CS-FCNTs-Fe3O4) was immobilized onto the GNPs layer by electrostatic interactions between amino groups of CS and GNPs. Because chitosan (CS) contains many amino groups, it can absorb more antibodies. FCNTs have high surface area, high electrical conductivity, and it can enhance the electron transfer rate; Magnetite (Fe3O4) nanoparticles can provide a favorable microenvironment for biomolecules immobilization due to their good biocompatibility, strong superparamagnetic property, and low toxicity; and GNPs possess high surface-to-volume reaction, stability, and high conductivity. Gold Nanoparticles/Fe3O4-FCNTs-CS composite film was constructed onto the GCE surface, which had significant synergistic effects toward immunoreaction signal amplification. The stepwise assembly process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Under the optimal conditions, the current response was proportional to the concentration of carbofuran ranging from 1.0 ng/mL to 100.0 ng/mL and from 100.0 ng/mL to 200 µg/mL with the detection limit 0.032 ng/mL. The proposed immunosensor exhibited good accuracy, high sensitivity, and stability, and it can be used for detection of carbofuran pesticide.

A Comparative Study of Modified Materials of Acetylcholinesterase Biosensor

In this study, multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and Prussian Blue (PB) were used for modifying glassy carbon working electrode (GCE) to construct acetylcholinesterase (AChE) biosensor respectively. Chitosan membrane was used for immobilizing AChE through glutaraldehyde cross-linking attachment to recognize pesticides selectively. Before the detection, the enzyme membrane was quickly fixed on the surfaces of modified electrode with O-ring to prepare an ampero-metric acetylcholinesterase biosensor for organophosphate pesticides. The fabrication procedures were characterized by cyclic voltammetry and amperometric i-t curve. The electrochemical behaviours of three modified sensors were compared, and the results showed that AChE-PB/GCE possessed higher oxidation peak current at a lower potential. Based on the inhibition of organophosphorus pesticides to the enzymatic activity of AChE, using dichlorvos as model compound, the sensitivity of three modified biosensors were compared, the results showed that the detection limit of AChE-PB/ GCE was lowest.

Comparative research on two kinds of amperometric immunosensor for detection of carbofuran residues

In this study, two kinds of novel label-free amperometric immunosensor for the direct detection of carbofuran was developed using layer-by-layer assembly and sol-gel technology, respectively. In one hand anti-carbofuran monoclonal antibodies were immobilized on the gold electrode (GE) surface which was modified with multilayers of L-cysteinewas, gold nanoparticles (nano-Au) and horseradish peroxidase (HRP) through layer-by-layer assembly technology, in the other hand, anti-carbofuran monoclonal antibodies were immobilized on the surface of the glassy carbon electrode (GCE) based on sol-gel technology to prepare non-labeled electrochemical immunosensor for the detection of carbofuran. The conformational properties of the immunosensor were characterized using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and a current response curve. Effects of experimental variables, such as concentration of antibody solution, pH of working buffer and incubation time, were studied in detail for optimization of analytical performance. Under optimal conditions, the current response was proportional to the concentration of carbofuran.