Glucose And Glycoprotein Sandwich Assay Using In Situ-Generated Raman Reporters

Surface-enhanced Raman scattering(SERS)spectroscopy has been widely applied in biological detection and molecular recognition due to high sensitivity,excellent selectivity,and less susceptibility to sample environment.Diabetes is a disease which is characterized by elevated blood glucose levels.It is known as a "silent killer".Glycoproteins are a large family of proteins.They play significant roles in many biological processes,such as,molecular recognition,cell signaling,immune response,and regulation of cellular development.As the expression of glycoproteins is associated with the occurrence of diverse diseases,many glycoproteins have been employed as disease biomarkers for clinical diagnosis.It is of great importance to detect glucose or glycoprotein sensitively and selectively.It is known that Ag nanoparticles(AgNPs)have high SERS activity,and Ag@Au core/shell nanoparticles take the advantage of high SERS activity of AgNPs and good biocompatibility of AuNPs.We choose AgNPs and Ag@Au core/shell nanoparitcles as SERS-active substrates,respectively.This thesis reports assays of glucose and glycoprotein using in situ-generated Raman reporters based on AgNPs and Ag@Au nanoparticles,respectively.(1)A facile and sensitive glucose sandwich assay using SERS spectroscopy has been developed through the self-assembled p-mercaptophenboronic acid(PMBA)monolayer on a smooth gold-coated slide and the SERS tags of AgNPs modified with p-aminothiophenol(PATP)and PMBA.The photocoupling product 4,4,-dimercaptoazobenzene(DMAB),generated in situ from PATP on the AgNP surface during the SERS measurement,possessed considerably intense characteristic SERS peaks and acted as the actual Raman reporter,which improved the sensitivity of glucose detection devoid of interference of other biomolecules.The facile sandwich assay showed a high selectivity of glucose over fructose and galactose.(2)Glycoprotein sandwich assay using SERS spectroscopy has been developed through the self-assembled PMBA monolayer on a smooth gold-coated slide and the SERS tags of Ag@Au nanoparticles modified with PATP and PMBA.The Ag@Au nanoparticles have been chose as SERS-active substrates,due to high SERS activity of AgNPs and good biocompatibility of AuNPs.The photocoupling product DMAB acted as the actual Raman reporter,generated in situ from PATP on the AgNP surface during the SERS measurement.Compared with Ag nanoparticles modified with PATP,the Ag@Au nanoparticles possessed considerably stronge characteristic SERS signals,which improved the sensitivity of glycoprotein detection.