Studies On Design And Application Of SERS-based Bio-sensing Method

Surface-enhanced Raman Scattering(SERS) is a fingerprint identification technique based on Raman scattering, it has the advantages of high resolution, high sensitivity and testing in the aqueous solution. SERS is very suitable for the research on the analysis of interface state, molecular orientation and configuration, etc.SERS technology has developed into a powerful tool for trace analysis, which has widely been used in the field of analytical chemistry, surface science and biomedical science. In recent years, with the continuous development of optoelectronics, nanotechnology and bioanalytical method, the studies on SERS-based bio-sensing have attracted considerable research efforts. In this thesis, we will propose a variety of SERS-based bio-sensing methods with high sensitivity and good selectivity using different biological ingredients as functional elements and probed targets based on their specific identification.The contents as follows:1. SERS technique is an important means to obtain the structure and species of molecular in biological system, and surface plasmon resonance(SPR) is an effective detection technology that is very sensitive to the changes of refractive index of materials adsorbed on the surface. Here, we put forward the SPR-SERS method with the combination of SPR and SERS to study the biological systems of avidin/biotin and the catalytic reaction process of chymotrypsin. The SPR-SERS bio-sensing method can improve the sensitivity by coupling the SPR to enhance SERS and get abundant information of the interaction between molecules.2. We propose a method of researching the immune recognition process using dielectric waveguide coupling localized surface plasmon resonance(LSPR) of metal nanoparticles to enhance SERS. In this structure, a layer of dielectric waveguide is laid onto the traditional Kretschmann prism, and metal nanoparticles are further assembled on the surface of waveguide layer after the immobilization of biological molecules. Under the assistance of waveguide resonance and LSPR, we get an enhancement of electromagnetic fields, which can be used to strengthen the SERS signals and improve detecting sensitivity.3. The study of "hot spots" occupies an important position in the mechanism of the electromagnetic field enhancement of SERS. Hot spots are generally located in the gaps of nanoparticles or on the tips of the nanostructures, where have a very strong enhancement factor. We use DNAzyme and its complementary substrate to form a rigid double-stranded DNA serving as bridge molecules or scaffolds to construct a smart structure of "silver nanoparticles- DNA- silver film". The catalytic reaction activated by lead ion changes the morphological of DNAzyme, causing silver nanoparticles fall to the silver film forming a smaller nanogap as an effective SERS hot spot. This process can be used for detection of lead ion with high sensitivity.4. SERS has many advantages such as no pretreatment of samples, high sensitivity, detection in aqueous solution, etc. The microfluidic chip technology can integrate the process of the reaction, separation and detection of sample into together. We combine the SERS and microfluidic chip technology to form an aptamer-based SERS microfluidic chip with specific aptamer as a functional element to capture and fix the analyte to the enhanced substrate. This aptamer-based SERS chip can be used for the selective and real-time detection of polychlorinated biphenyls(PCBs).