The Study On Immunosensor For Carbofuran Residues Detection

Carbofuran is a broad-spectrum insecticide widely used in agriculture to control pests in horticultural crops for the production and the control of insect-borne diseases. The improper use and abuse of carbofuran and the effect of food chain enrichment lead to the serious residuse of carbofuran. The presence of carbofuran in food receives worldwide attention. Compared with conventional methods for determination of carbofuran, electrochemical immunosensors have many advantages including simple instrumentation, easy operation, rapid response, high sensitivity, selectivity and high compatibility with advanced nanotechnology and micromachining technologies. In this study, we study on the electrode modification and antibody immobilization in order to select the optimal methods for the fabrication of immunosensor.(1).The deposited gold nanocrystals (DpAu)/4,4’-thiobisbenzenethiol (DMDPSE) multilayers ({DpAu/DMDPSE}n) membranes were used for modifying Au electrode to fabricate amperometric immunosensor. DpAu/DMDPSE multilayers were modified by layer-by-layer self-assembly technology. Under optimized conditions, the detection limit was0.06ng/mL.The advantages of the immunosensor were exhibited in its wider linear range, better specificity, reproducibility and stability.(2).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’s Fc fragment. Following, antibody was immobilized on the PA modified electrode and then blocked by bovine serum albumin (BSA). With the excellent electroconductivity of DpAu and the PA’s oriented immobilization of antibodies, the 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 detection limit was0.1924ng/mL.(3).A novel amperometric immunosensor was developed for the detection of carbofuran. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethylene imine 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 synergic effect in the electrochemical performance. Then the electrode was coated with gold nanoparticles-antibody conjugation (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was immobilized covalently to AuNPs by glutathione used as a spacer arm. Under optimal conditions, the detection limit was0.03ng/mL (S/N=3).(4).Based on the three experimental scheme mentioned above, the optimal fabrication method was screened out through analyzing and comparing the experimental results. Firstly, MWCNTs and GS-PEI-Au nanocomposites were modified onto the surface of GCE. Then the electrode was coated with PA used for binding antibody’s Fc fragment. Finaly, the electrode was coated with anti-carbofuran antibody and blocked with BSA. This process is simple, easy and needs fewer reagents. All of these have shortened the fabrication period. Due to the high stability of PA, after several regeneration times, the electrode was immobilized with antibody again and ensure that the bioactivity of antibody.