Abstract
In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD), ultraviolet and visible absorption spectroscopy (UV-vis) and scanning electron microscopy (SEM), respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3). The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.
Highlights
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) is a broad-spectrum insecticide widely used in agriculture
We introduce a multiwall carbon nanotubes (MWCNTs), graphene sheets (GS)-PEI-Au nanocomposites and AuNPs-antibody conjugate-modified amperometric immunosensor for the detection of carbofuran
The electrochemical immunosensor was prepared by the following steps: (i) before the surface modification, glass carbon electrode (GCE) was first polished with 0.5 and 0.03 μm alumina slurry, respectively, rinsed thoroughly with absolute alcohol and distilled water in an ultrasonic bath, and dried with N2 at room temperature. (ii) 10 μL of MWCNTs were initially dropped on the electrode surface, and dried under an infrared lamp
Summary
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) is a broad-spectrum insecticide widely used in agriculture. In order to develop a high-performance amperometric immunosensor, signal amplification and immobilization of Ab or hapten are vital in optimizing the analytical performance characteristics, such as response, reproducibility, stability, selectivity and regeneration [5]. With the development of nanotechnology, a variety of nanoparticles, such as multiwall carbon nanotubes (MWCNTs), graphene sheets (GS) and gold nanoparticles (AuNPs), have been widely used in the fabrication of immunosensors [6,7]. It is preferable to maintain the high biological activity of the immobilized biomolecules and enhance the sensitivity of the immunosensor, but the chitosan film is not electrically conductive. In recent years MWCNTs were introduced in chitosan film to improve its electric conductivity [12]
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