Labeled Photoelectrochemical Immunoassay Based On Semiconductor Nanomaterials

Photoelectrochemical biosensing is a new kind of biosensor technique, which is developed on the combination of photoelectrochemical process and specific biorecognition. Its sesing principle depends on the fact that the electrical signal change could be produced by the biological interactions between recognition elements and their corresponding target analytes. Compared with traditional optical methods, photoelectrochemical biosensing has attracted growing research interests because it has exciting features of simple equipments, low cost, easy miniaturization, low background signal and high sensitivity. To date, many different kinds of photoelectrochemical biosensors were reported and various target analytes such as biomarkers, DNA sequences and cells were successfully detected. In this thesis, different signal amplification elements were designed and used as labels to further promote the sensitivity of the immunosensor. The main contents were described as below:1. Highly sensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V2+ conjugatesTiO2 nanowires (TiO2NWs) obtained by hydrothermal growth method were first coated on an ITO electrode. After Au nanoparticles were deposited on the surface of the TiO2NWs film to form TiO2NWs/Au hybrid structure. CdSe@ZnS quantum dots (QDs) were then mofidied onto the electrode via layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V2+) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V2+ conjugates, which were used as signal amplification elements. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V2+ conjugates, the designed photoelectrochemical immunoassay exhibited an ultralow detection limit as well as good specificity, reproducibility and stability for CA19-9 detection. The photoelectrochemical platform is highly expected to apply in the design of various photoelectrochemical immunoassays, especially for the detection of trace levels of disease-related biomarkers.2. Enhanced photoelectrochemical sandwich immunosensor based on CdSeTe@CdS:Mn core-shell quantum dots sensitized TiO2 amplified by the labels of CuS nanocrystalsTiO2 nanoparticles were first coated onto a bare ITO electrode and the compact film was formed after high temperature sintering. CdSeTe alloyed quantum dots (AQDs) were then deposited on the ITO/TiO2 electrode via electrostatic adsorption assisted by oppositely charged polyelectrolyte, and then further deposited with CdS:Mn shells on the surface of CdSeTe AQDs via successive ionic layer adsorption and reaction, forming sensitization structure of TiO2/CdSeTe@CdS:Mn, which was used as photoelectrochemical matrix to immobilize capture CEA antibodies (Ab1); signal CEA antibodies (Ab2) were labeled with CuS nanocrystals (NCs) to form Ab2-CuS conjugates, which were employed as signal amplification elements when specific immunoreaction occurred. Due to synergy effect of TiO2/CdSeTe@CdS:Mn sensitization structure and excellent signal amplification of Ab2-CuS conjugates, the photoelectrochemical immunosensor showed an ultralow detection limit for CEA detection, and it also exhibited good specificity, reproducibility and stability.