| Surface-enhanced Raman scattering (SERS) is a highly sensitive and selective tool for the identification of biological or chemical analytes based on Raman scattering. Its narrow, well-resolved bands, low SERS intensity of water and high stability make SERS widely used in material science, surface science, analytical chemistry,biological characterization and diagnostics. Piezoelectric biological sensor has the characteristics of simple, rapid, sensitive, low cost, to respone in a broad spectrum, real-time data output, etc., with wide application prospects in the biological technology, clinical diagnostics, environmental monitoring, food industry, medicine and military fields. This thesis focuses on how to improve the detection sensitivity of a biosensor, by using of nano-materials. We have developed two new SERS biological sensors for Pb2+, and adenosine, and a piezoelectric PDGF-BB biosensor. The details are summarized as follows:1. In chapter two, We have developed a novel multi-layer metal - molecule - metal nano-junction for the ultra-sensitive Pb2+ SERS detection. In this chapter GR-5 DNA enzyme was assembled on gold electrode surface, as a specific recognition probe for Pb2+. The presence of Pb2+ can be embedded in the DNA enzyme catalyzed substrate hydrolysis chain of RNA bases, and it was cut into two parts. Gold electrode surface, the remaining part of the nucleic acid fragments can be the report of gold nanoparticle probes labeled hybridization chain. Taking advantage of the hybridization between two complementary DNA strands, the Raman signal of their terminal tag molecules was significantly enhanced with the formation of the metal-molecule-metal NJs between Au nanoparticles (NPs) capped by them. A detection limit towards Pb2+ has been obtained as low as 1.0×10-10 M.2. In chapter three, Aptamer and the gold electrode surface of the first capture probe complementary hybrid is fixed on the electrode surface, when the presence of adenosine, and the occurrence of specific binding aptamer, resulting in configuration changes, off from the electrode surface. Then the capture probe can be labeled the report of the gold nanoparticles hybridization probe chain, the same through the layers of self-assembled nanostructures, leading to a significant enhancement of Raman signals. The sensor has good selectivity detection limit is 5.0×10-8 M. 3. In chapter four, We propose a simple antibody and aptamer-based sandwich-type piezoelectric immunosensor for the detection of PDGF-BB. In this method, the quartz crystal surface was coated with a self-assembled monolayer of 3-mercaptopropionic acid (MPA) for covalently immobilization of the PDGF-BB antibody, Then the quartz crystal surface was activated by incubating with EDC/NHS. And then through the MPA on PDGF-BB antibody carboxyl and amino response on combined analysis of its solution can specifically recognize the PDGF-BB, followed by a 1-h incubation at room temperature with BSA solution to saturate unreacted binding groups on the gold surface. Subsequently, binding with the nano-gold labeling of PDGF-BB aptamer specifically. The sensor on the concentration of PDGF-BB detection range of 0.05 5μg/mL, the detection limit is 1.0×10-3μg/mL. |
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