Preparation Of Bimetallic SERS Nanoprobes And The Applications In Bioanalysis

Surface-enhanced Raman scattering(SERS)is generally considered to be a molecular-specific spectroscopy technique,enchanced by electromagnetic and chemical effects.Taking the advantage of unique molecular vibration fingerprinting,SERS could be using to quickly detect as low as trace amounts of analytes.The application of SERS in bioanalysis involves the complex interaction of functional SERS substrates with biological systems and the environment.Therefore,the preparation of SERS substrates with good stability,reproducibility and sensitivity has become the key to reliable bioanalysis.In this study,we have proposed the stable SERS active substrates with functionalized modification and applied to the ultrasensitive detections of human papillomavirus-specific nucleic acid fragments and multiple exosomes.The main research content includes the following two parts:1.Preparation a novel strategy for the synthesis of SERS nanotags by embedding bilayer Raman reporter molecules in Au@AgAgNR(gold core and bilayer silver shells nanorod structure).Based on the sandwich hybridization assay,probe DNA-conjugated SERS nano tags used as SERS detection probes and capture DN A-conjugated magnetic beads(MBs)used as capture probes via a streptavidin-biotin bridge.Finally,detection probes,target HPV-16,and the capture probes are recognized and base paired to form "sandwich"nano-assembly structures to achieve specific detection of the target HPV-16.The capability for detection of the cervical cancer related-HPV with the high sensitivity and specificity was demonstrated using the proposed SERS sensor.The experimental results indicated that the proposed strategy holds significant potential for the detection of cervical cancer and o ffers the opportunity for future applications in clinical diagnosis.2.Preparation of oligonucleotide aptamer-based SERS biosensors and the application of multiple exosomes detection.Firstly,the gold nanotrepangs(GNTs)with rough surface were synthesized by the mediation of sulfhydryl DNA.And then the double-layer Raman reporter molecules and double-layer silver shells were modified layer by layer on the surface of GNTs to form bimetallic nanotrepangs(gold-silver-silver nanotrepangs,GSSNTs)with high SERS activity.SERS detection probes were prepared via functionally modifing linker DNA sequences on the surface of GSSNTs,which were partially complementary with aptamers.In addition,SERS capture probes capable of recognizing multiple target exosomes were constructed by functionally modifing specific aptamers on the streptavidin-modified magnetic beads.Furthermore,the SERS detection probe was tightly coupled to the capture probe to form a multiplexed SERS sensor.When the target exosomes were present,detection probes were released into the supernatant,which causing decrease of SERS signals on the MBs.The proposed SERS-based sensor is a pro mosing for screening of multiple exosomes of cancer cells.