Designs Of Sers-based Biosensor For Biomolecules Employing DNA Triple-Helix

Surface-enhanced Raman scattering (SERS) is a highly sensitive and selectivetool for the identification of biological or chemical analytes based on Raman scattering.Its narrow well-bands, low SERS intensity of water and high stability make SERSwidely used in the fields of material science, analytical chemistry, biologicalcharacterization, and diagnostics, etc. Nucleic acid probes have been increasinglyapplied in a broad range of fields in chemistry, biomedicine, disease diagnosis andtreatment due to their simple design, good stability, easy synthesis, and flexible signalmechanism. In this thesis, novel and sensitive detection methods have been proposedcombining SERS and flexible signal mechanism of nucleic acid probes. The contentsof the thesis are as followed:(1) A strategy that combines Triple-Helix and SERS has been developed toamplify signal enhancement and detect DNA. This approach utilized the Triple-Helixconfiguration between a capture DNA and a hairpin DNA that one end is coupled to agold nanoparticle (AuNP) surface and tagged a Raman reporter, Rox, at the other endin the absence of target DNA, separating the Raman label from the nanoparticle andcausing a quenching of the SERS signal upon laser excitation. In the presence of targetDNA, because of the hybridization of the capture DNA and target DNA, the hairpinstructure keeps freedom state and the Raman label is in proximity to the nanoparticle,which induces a strong SERS effect on the adjacent Raman label molecule.(2) A novel SERS approach for detection of ATP has been developed combiningtriple-helix and SERS enhancement based on the “hot spot” theory that generatedbetween silver nanoparticles (AgNPs) and Au film, and Rox was employed as theRaman reporter. In the absence of ATP, a rigid structure was formed betweenATP-aptamer and the substrate probe that attached to a AgNP with a freedom end andmade AgNPs far from Au film, causing a very weak Raman signal. Interaction of theaptamer with ATP releases the SERS-HP that took the AgNP more closely to the Aufilm surface, and as a result, a significant Raman signal enhancement was observed.This assay implemented highly sensitive and selective detection of biomolecule andthe universality of the approach is achieved by virtue of altering the loop sequence ofcapture DNA without change of the triple-helix structure.