The Research For The Determination Of Aflatoxin And Protein Using Electrochemical Immunosensors

Electrochemical immunosensors have many advantages such as: selectivity, variety, low-cost, not affected by the color and turbidity of samples, equipment required is relatively simple, fast and small. They could be widely used in areas such as medical, food analysis, industrial production, environmental testing. In this paper, we developed electrochemical immunosensors for the detection of aflatoxins and platelet-derived growth factor (PDGF). The main contents are as follows:(1) A sensitive and simple electrochemical immunosensor based on enzymatic silver deposition amplification was constructed for the detection of aflatoxin B1 (AFB1) in rice. AFB1-BSA was first immobilized on the electrode surface. Then, an indirect competitive reaction between free AFB1 and AFB1-BSA immobilized on the electrode surface for binding to a fixed amount of anti-AFB1 antibody was occurred in order to immobilize antibody on the electrode. The alkaline phosphatase (ALP) labeled anti-mouse IgG secondary antibody was bound to the electrode surface through reaction with primary antibody. Finally, ALP catalyzed the substrate, ascorbic acid 2-phosphate, into ascorbic acid that reduced silver ions in solution to metal silver deposited onto the electrode surface. Linear sweep voltammetry (LSV) was carried out to quantify the metal silver, which indirectly reflected the amount of the analyte. At the optimal conditions, the working range of the electrochemical immunosensor was from 0.1ng/mL to 10ng/mL. Good recoveries were obtained for the detection of spiked rice samples. This method is simple, cost-effective, and could serve as a screening approach for this type of mycotoxins.(2) An amperometric immunosensor was constructed for aflatoxin B1 determination. First, AFB1-BSA was immobilized on the electrode surface. Then, antibody was immobilized on the electrode by specific reaction between antigen and antibody. The horseradish peroxidase (HRP) labeled anti-mouse IgG secondary antibody was bound to the antibody on the electrode surface. At last, HRP catalyzed H2O2 to oxidize hydroquinone into p-benzoquinone. Subsequently, p-benzoquinone at the electrode is reduced, resulting in reduction current which could quantify the analyte. The proposed amperometric measurements are simple to be used and could serve as a screening approach for this type of mycotoxins.(3) An electrochemical immunosensor based on combination of aptamer and enzymatic silver deposition amplification was constructed for detection of platelet-derived growth factor (PDGF), which is one of the cancer marks. First, anti-PDGF antibody was immobilized on the electrode. Then, the modified electrode was successively incubated in PDGF samples, biotin-labeled aptamer, and avidin-labeled alkaline phosphatase solution. Finally, the resulting electrode was incubated in fresh prepared substrate solution for enzymatic silver deposition. Linear sweep voltammetry (LSV) was carried out to get the electrochemical signals. The method is sensitive, simple, and selective with wide linear range, low detection limit. Thus, it has a good application prospects in the early diagnosis of cancer.