The Study On Label-free Amperometric Immunosenser For Carbofuran Detection

In this study, the new research progress on immunosensor has been reviewed briefly, and took use of self-assembly, sol-gel and electroplating technology to construct immunosensor for carbofuran detection. The nanogold, multi-walled carbon, chitosan and so on were used to improve the performance of the immunosensor.(1) 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. L-cysteine was deposited onto the surface of a gold electrode by Au-S bond to immobilize GNPs onto the electrode. The GNPs linking with L-cysteine formed more electron transfer tunnels to enhance the electrocatalytic response of the immunosensor. Under optimal conditions, the current response was proportional to the concentration of carbofuran which ranged from0.01ng/mL to50ng/mL with correlation coefficient of0.9912. The detection limit was0.01ng/mL (S/N=3).(2) In this part, 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 Ab/SiSG/GCE immunosensor for the direct determination of carbofuran was developed by a step immobilize. 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. Under the optimal conditions, the linear range of the proposed immunosensor for the determination of carbofuran was from1ng/mL to100μg/mL and from50μg/mL to200μg/mL with a detection limit of0.33ng/mL (S/N=3).(3) An electrochemical immunosensor has been developed for the determine-ation of carbofuran based on gold nanoparticles (GNPs), prussian blue-multiwalled carbon nanotubes-chitosan (PB-MWCNTs-CTS) nanocomposite film and protein A (SPA) layer by layer assemble technology. GNPs, PB and MWCNTs-incorporated films were used to enhance the electroactivity and stability of the immunosensor. The porous three-dimensional PB-MWCNTs-CTS nanocomposite film provided many amino groups and carboxyl groups to cross-link SPA and offered a large specific surface area to immobilize SPA. The formation of a self-assembled SPA layer was employed onto the electrode surface to increase the binding capacity of antibody. Effects of experimental variables were investigated in details. Under optimum operating conditions the system provided a wide linear range between0.1ng/mL and1μ.g/mL with a low detection limit of0.021ng/mL(4) In this study, an anti-carbofuran monoclonal antibody (Ab) was immobilized on the surface of a gold electrode surface using layer-by-layer assembly technology. Thus, immunosensor was based on gold nanoparticles (DpAu),4,4’-Thiobisbenzenethiol-3-Mercaptopropionic acid (MPA)-gold colloidal nanoparticles (GNPs) netshaped nanocomposite film and protein A (SPA). DpAu was used to enhance the electroactivity and stability of the immunosensor. The porous three-dimensional netshaped nanocomposite film provided many amino groups and carboxyl groups to cross-link immobilize SPA. The formation of a self-assembled SPA layer was employed onto the electrode surface to increase the binding capacity of antibody. Effects of experimental variables were investigated in details. Under optimum operating conditions, the system provided a wide linear range between0.1ng/mL and10ug/mL with a low detection limit of0.0068ng/mL(S/N=3).