Abstract
In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.
Highlights
An immunosensor is a kind of biosensor that provides concentration-dependent signals by using antibodies (Ab) or antigens (Ag) as the specific sensing element [1,2]
There was an obvious increase of the amperometric current after multi-walled carbon nanotubes (MWCNTs)-THI-CHIT composite was coated onto the glassy carbon electrode (GCE) compared with the bare GCE, indicating that the use of MWCNTs significantly enhanced the electrical conductivity of the electrode [35]
After GA was dropped on the MWCNTs-THICHIT/GCE and Ab were immobilized on the layer, the peak current obviously decreased due to GA and Ab hindering the shuttle of electrons to the electrode surface
Summary
An immunosensor is a kind of biosensor that provides concentration-dependent signals by using antibodies (Ab) or antigens (Ag) as the specific sensing element [1,2]. Semiconductor multi-walled carbon nanotubes (MWCNTs), have unique electrical and mechanical properties, high surface area, and are proven to promote electron transfer between electrochemically active compounds and electrodes [16,17,18]. Cao et al have developed an electrochemical immunosensor using poly(L-arginine)/multi-walled carbon nanotubes composite film with functionalized gold nanoparticles for the sensitive detection of casein [19]. It is reported that CHIT-MWCNTs [24,25,26,27] has been used for fabricating various biosensors as they can provide a suitable microenvironment for immobilizing biomolecules and promoting electron transfer to enhance the sensitivity of the immunosensor. Huang et al have designed a disposable electrochemical immunosensor for the detection of carcinoembryonic antigen based on Au nanoparticles/multi-walled carbon nanotubes-chitosan composite films [29]. Real sample analysis was performed to evaluate the proposed immunosensors
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