Abstract
In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu) was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA) and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA) was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. With the excellent electroconductivity of DpAu and the PA’s oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.
Highlights
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) is a broad-spectrum insecticide widely used in agriculture to control pests in horticultural crops to enhance production and control of insect-borne diseases
The electrodes were immerged in 0.1 M citrate buffer solution (CBS, pH 2.7) for 5 min, in order to separate antigen-antibody complex from the protein A (PA) surface, and immobilized anti-carbofuran refering to the above steps for carbofuran detection
DpAu with large specific area and high electrical conductivity could improve the conductivity of the electrode, after DpAu were deposited onto Au electrode, the charge transfer resistance (Rct) decreased, demonstrating that DpAu have been successfully assembled on the bare Au electrode, which is consitent with previous reports [24]
Summary
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) is a broad-spectrum insecticide widely used in agriculture to control pests in horticultural crops to enhance production and control of insect-borne diseases. The presence of carbofuran in food has received worldwide attention because of its relatively high solubility of 700 mg/L in water at 25 °C and the fact it is a systemic insecticide, which can be absorbed by roots, steams and leaves and transmit and translocate in ther plant. Carbofuran can cause acute toxicity to human through cholinesterase inhibition [1,2]. Monitoring of pesticide residues in vegetables for evaluation of vegetable quality so as to avoid possible risks to human health is a priority objective [3]. Current analytical methods for carbofuran detection involving gas chromatography (GC) and high performance liquid chromatography (HPLC). There is a growing demand for more rapid and economical methods for detecting pesticide residues
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