Study On Electrochemical Immunosensor Of Gold - Antibody Nanocomposite

Electrochemical immunosensors, which combined the merits of electrochemical technology and immunoassay, have been widely studied including clinical diagnosis, bioassay and environmental monitoring. They have many advantages such as fast analytical time, high sensitivity, low-cost and high selectivity, and convenient operation. As for the construction of an electrochemical immunosensor, the key factors are the strategies and materials used to immobilize biomolecules. Nanomaterials, which exhibit good biocompatibility, large specific surface area and strong adsorption capacity, are favourable for constructing biosensors. In this paper, we fabricated some immunosensors using several nanomaterials such as gold nanoparticles which was prepared by liquid-liquid interface method, graphene, and graphene oxide for the immobilization of biomolecules. The preparation of immunosensor process and its characterization were investigated. The results showed that the sensitivity and stability of the immunosensor were well acceptable.The main works are listed as follows:1. Gold-antibody nanocomposite thin film fabricated by liquid-liquid interface technique and its application for sensitive immunoassay of alpha-fetoprotein (AFP)A sandwich-type electrochemical immunosensor for the detection of alpha-fetoprotein based on Au-antibody nanocomposite thin film which was prepared by liquid-liquid interface method was developed. Through the interaction between gold nanoparticles and-NH2terminated antibodies, antibodies were effectively combined with Au on the thin films. The synthesis of AuNPs combining antibodies on the liquid-liquid interface facilitated the Au-antibody (Au-Ab1) nanocomposite arrangement orderly, which was attributed to a high degree of molecular level controlled by the necessary interfacial interactions and flexibility. The monodisperse Au-Ab1composite thin films were extracted up by ITO. The Au-Ab] composite thin films not only simplified the immobilization process but also amplified the detection signal. Under the optimal conditions, the linear response range was from1to250ng·mL-1for AFP detection. The detection limit was0.5ng·mL-1. The immunosensor showed good selectivity, reproducibility and stability. And it could be used to detect clinical serum samples with good accuracy.2. Graphene/gold-antibody nanocomposite thin film and functionalized graphene oxide as a nanocarrier for highly sensitive electrochemical immunosensorAn electrochemical immunosensor using graphene sheet and gold-antibody nanocomposite thin film which was prepared by liquid-liquid interface method, and functionalized graphene oxide (GO) labeled with horseradish peroxidase-secondary antibodies (HRP-Ab2) for sensitive detection of cancer biomarker was constructed. Both the graphene and the AuNPs thin film provide a large surface area for capturing a large amount of Ab1and amplify the detection signal. The improving sensitivity was achieved by using the multibioconjugates of GO-HRP-Ab2onto the electrode surface through a sandwich-type immunoreaction. The proposed method could detect AFP with a linear range from0.005to200ng·mL-1with a low detection limit of1.2pg·mL-1. The immunosensor showed good selectivity and reproducibility, and it also can application in clinical diagnostic.