Functionalized Poly(O-phenylenediamine) Nanocomposite-modified Immunosensor For Electrochemical Detection Of Tumor Markers

Tumor marker, as a substance that produced by cancers or other cells of the body in response to cancer or certain benign (noncancerous) conditions, is usually used to determine, diagnose, and manage some types of cancer. Therefore, the detection of tumor marker is very important.Electrochemical immunoassay, due to its low cost, low detection limit and high selectivity, has attracted considerable interest. The basic principle is to detect antigen or antibody by the electrochemical method based on the labeled immune-reagents/ enzymes, and other electro-active substances. Compared with other polymers, poly(o-phenylenediamine) (PoPD) contains many free amino and imino groups and expresses good stability and high conductivity. Therefore, PoPD has been employed for the preparation of the biosensors. In this thesis, we report the proof-of-concept of several new electrochemical immunoassay strategies and protocols for the detection of low-abundance proteins by coupling with the merits of poly(o-phenylenediamine) for the amplification of detectable signal. The thesis consists of 4 chapters as follows:The first chapter mainly consists of (i) tumor markers and the present detection method, (ii) electrochemical immunosensor and the recently advanced development, (iii) poly(o-phenylenediamine) and its preliminary application in electrochemical immunoassay, and (iv) the main research contents in this thesis.The second chapter constructs a new class of redox-active magnetic nanostructures for high-efficiency electrochemical immunoassay of carcinoembryonic antigen (CEA). The assay was based on a sandwich-type immunoassay protocol by using nanogold-patterned graphene oxide nanoscales (AuNP-GO), conjugated with horseradish peroxidase-labeled anti-CEA, as secondary antibodies and biofunctionalized magnetic nanostructures as immunosensing probes. Under optimal conditions, the nanoparticle-based immunocomposites exhibited good electrochemical responses for detection of CEA with the dynamic range of 0.01-40 ng mL"1 and the detection limit of 0.001 ng mL-The third chapter reports a new electrochemical immunoassay for the detection of prolactin (PRL) by using poly(o-phenylenediamine)-carried nanogold particles (GPPD) labeled with biomolecules as signal tags on poly(lysine) (PLL)/gold nanoparticles-functionalized immunosensor. Under the optimal conditions, the developed immunoassay exhibited good electrochemical behaviors toward PRL in the dynamic range of 0.5～180 ng mL-1 with a detection limit of 0.1 ng mL-1.The fourth chapter develops a new electrochemical immunoassay by using gold nanoparticles/poly(o-phenylenediamine)/graphene oxide composites (GNPG) labeled biomolecules as signal tags, and dendritic gold nanoparticle structure (HDGM) as immunosensing interface. With a sandwich-type immunoassay format, the developed immunoassay displayed good electrochemical response toward CEA standards in the dynamic range of 0.005～80 ng mL-1 with a detection limit of 0.5 pg mL-1.