Preparation Of Highly Sensitive Surface-Enhanced Raman Scattering(SERS) Nanoprobes And Its Application In Bioanalysis

Surface enhanced Raman scattering(SERS)is a spectral technique with the specificity of molecular fingerprints and the ability to detect single molecule.It has the advantages of simple operation,high spectral resolution,few samples and many components can be detected at the same time.It has been widely applied in food safety,environmental detection,biomedicine and other fields,and has become a powerful rapid analysis and detection tool.In recent years,the preparation of SERS substrates with high SERS effect,good stability and reproducibility has become a hot research topic.On the base of the traditional SERS substrate preparation,it has become the key to expand the application field of SERS technology to construct the nanoprobes with high SERS activity through some functional modifications.The purpose of this paper is to design and construct high SERS active probes and apply them to sensitive detection and analysis of small biomolecules and disease biomarkers.The main research contents include:1.Construction of the "core-satellite"-like assembly and its application in the detection of adenosine triphosphate(ATP)with high sensitivity.As an important energy carrier,ATP provides energy for various biochemical reactions in the body and quantitative detection of ATP is of great significance.Firstly,the gold nanoparticles(AuNPs)and the silver-coated gold nanoparticles(AuNS@Ag)with high SERS effect were prepared respectively,and the ATP nucleic acid aptamers were devided into two-segment probes as response elements,which were assembled on the surfaces of AuNPs and AuNS@Ag particles by modifying sulfhydryl groups.At the same time,Raman report molecules 4-mercapto benzoic acid(4-MBA)were immobilized on the surface of AuNPs by Au-S bonds.When ATP exists in the reaction system,two segments of single chain probes are specifically bonded through ATP molecules to induce AuNPs and AuNS@Ag particles to form "core-satellite" assembly.Because of the nanoscale gaps between AuNPs and AuNS@Ag particles,it can produce a lot of "hot spots",and then produce a strong SERS effect,thus achieving the specific detection of ATP.The detection limit of this method is 0.5 pM,and it has a good reproducibility.2.Preparation of cholesterol-functionalized SERS nanoprobe and its application in the detection of exosomes.By means of "seed" mediated growth method,4-MBA labeled and core-shell bilayer nanoparticles were synthesized.4-MBA as Raman reporters were embedded in the nanogap between the AuNS core and the Au shell,forming a large number of "hot spots",which can generate SERS enhancement effect.Cholesterol labeled double stranded nucleic acid probes were assembled on the surface of AuNS@4-MBA@Au particles via their sulfhydryl groups to prepare nanoprobes with high SERS activity.When exosomes exist in the reaction system,the immunomagnetic beads modified by the CD9 antibodies first capture the exosomes by affinity with CD9 proteins on the exosome membrane.Then,the AuNS@4-MBA@Au particles were added to the system to anchor on the surface of the exosomes through the hydrophobic interaction of the assembled cholesterol probes,and the "sandwich" structure was formed with the magnetic beads.By detecting the SERS signal intensities in the reaction system,the specific detection of exosomes was realized,the detection limit of this method is 27 particals/?L.