Construction Of DNA-mediated SERS Biosensors And Application In Tumor Biomarker Micro RNA Detection

In this thesis,two new detection strategies based on surface-enhanced Raman scattering biosensors were developed for simultaneous,ultrasensitive,and rapid detection of multiple biomarkers mi RNAs of liver cancer and colon cancer.The main contents include:（1）In Chapter 1,tumor and the importance of detection of tumor biomarkers was introduced,then,advantages and drawbacks of its traditional analysis methods and technologies were expounded.Afterward,based on the drawbacks of traditional detection methods,the key points and development trends of analysis techniques are discussed.Then,surface-enhanced Raman spectroscopy and its detection principles were introduced,and its merits and current application in mi RNA detection are introduced respectively.Finally,the research ideas were proposed.（2）In Chapter 2,a variety of nanomaterials were synthesized,including gold nanoparticles（Aunanoparticle,Au NP）,gold bridged nanoparticles（Au-NNPs）,Fractal gold nanoparticles（F-Au NPs）,silver nanocubes（Ag nanocube,Ag NC）,gold nanocage（Au nanocage,Au NC）,magnetic nanoparticles（Fe₃O₄）,and Ag-coated magnetic nanoparticles（Ag MNPs）,laid the foundation for later research.（3）In Chapter 3,based on the complementary pairing principle,complementary DNA-modified DNA-mediated SERS probes and Ag-coated magnetic nano-substrates and target mi RNA constructed a SERS sensor for simultaneous detection of three liver cancer mi RNAs.DNA-mediated synthesis of F-Au NPs with a core-shell structure and Ag MNPs were used as SERS probes and magnetic capture substrates.With the simultaneous detection of three liver cancer-specific mi RNAs（mi R-122,mi R-223,and mi R-21）as the detection target,SERS probes and substrate functionalized complementary DNA of the three mi RNAs for detection.F-Au NPs as SERS signal probes have the characteristics of high SERS enhancement and high stability.Ag MNPs retain good magnetic separation ability and also have the high Raman activity of the Ag shell.The detection limit is as low as amol/L,lower than most simultaneous detection methods currently reported.Also,the method exhibits excellent selectivity and specificity for target mi RNA and has high accuracy when applied to the detection of actual human serum samples.This method was successfully applied to the detection of 92 real liver cancer samples,showing its potential in clinical applications such as early diagnosis and monitoring of cancer.（4）In Chapter 4,based on the signal amplification strategy of gold nanocube cage assembly clusters,we constructed a surface-enhanced Raman scattering biosensor for two colon cancer biomarkers mi RNA（mi R-21 and mi R-31）.First,Ag nanocube（Ag NC）was synthesized,and Au nanocage（Au nanocage,Au NC）with hollow pore wall structure was prepared by an electrochemical displacement reaction.Using the Ag-coated magnetic nanoparticles prepared in the previous work as the substrate,signal probes and signal amplification probes are prepared by functionalizing complementary DNA strands on Au NC,gold nanocage assembly clusters were formed,which greatly enhances the SERS signal.The detection limit of mi RNA reaches amol/L level.Besides,this method exhibited great selectivity and specificity for target mi RNA and has high accuracy when applied to the detection of actual human serum samples.（5）In Chapter 5,the research content,merits,and application prospects of this work were summarized,the deficiencies in the current research were analyzed,then the follow-up research work were prospected.