Ag Nanorods Array Electrodes-based SERS/electrochemical Dual-mode Biosensors For Gastric Cancer Markers Detection

The reliable detection of cancer-related biomarkers such as miRNAs is essential for accurate diagnosis of cancers.However,the abundance of biomarkers especially miRNAs is extremely low in blood,and the development of high-sensitive and reliable technologies to detect trace miRNAs is urgently required.Surface-enhanced Raman spectroscopy（SERS）and electrochemical technologies are known as high sensitivity sensing tools,and the SERS/electrochemical dual-mode sensing can provide a powerful tool to achieve more accurate detection by cooperating with the advantages of the two modes,which can avoid failures of single mode and enhance the integrality and reliability of the test results for accurate and reliable detection of cancer-related miRNA at early stage of cancer.In this thesis,novel SERS/electrochemical dual-mode biosensors based on SERS-active Ag nanorods（AgNRs）array electrode were proposed for detection of gastric cancer-related miR-106a.The research is focused on the following two consents:（1）SERS/electrochemical dual-mode biosensor based on multi-functionalized molybdenum disulfide nanosheet probes and AgNRs array electrodesA novel SERS/electrochemical dual-mode biosensor based on multi-functionalized molybdenum disulfide nanosheet（mF-MoS₂ NS）probes and SERS-active Ag nanorods（AgNRs）array electrode was proposed to meet the needs of multi-mode reliable cancer-related miRNA detection.The AgNRs array coated by mF-MoS₂ NSs shows significantly improved electrochemical and SERS stability,and then the“mF-MoS₂ NSs probes-miRNA-AgNRs array electrodes”sandwich structured SERS/electrochemical sensor was built for stable dual-mode detection of miR-106a.The sensor shows good selectivity for differentiating miR-106a from single-base mismatched nucleic acid and shows the miR-106a concentration-dependent SERS and electrochemical signal ranging from 100 fM to 100 nM.The curves of both SERS and electrochemical sensing modes were fitted to be I₁₆₂₂=1000.23×Log C_miR-106a+13526.20（R²=0.998）andΔI=13.36×Log C_miR-106a+209.33（R²=0.994）with limit of detections of 67.44 fM and 248.01 fM,respectively.The reliable assay of miR-106a in human serum indicates that the proposed SERS/electrochemical dual-mode sensor is suitable for detecting complex samples and can be a potential high-sensitive and reliable tool for clinical diagnosis of early cancers.（2）DNA walker-amplified highly sensitive SERS/electrochemical dual-mode sensorA SERS/electrochemical dual-mode sensor powered by DNA walker amplification is proposed for highly sensitive and reliable detection of trace cancer-related miRNA.The sensor includes the sensing substrate,DNAzyme,and SERS/electrochemical two-mode probe（MPA@MB-H2）.Among them,the sensing substrate was prepared by assembling LWs and hairpin DNAs H1 on the AgNRs,followed by blocking the bare sites on the AgNRs by MCH.In the presence of target miR-106a（T）,LW captures the target and further binds DNAzyme,forming a stable LW/T//DNAzyme complex on the sensing substrate,and then the DNAzyme is constantly cutting the surrounding H1 with the help of Zn²⁺,leaving a large number of residual H1 fragments on the substrate,namely DNA walker signal amplification.The residual H1 fragments then hybridize with H2 immobilized onMPA@MB,so that MPA@MB can be captured on the sensing substrate and output strong SERS and electrochemical dual-mode signals.The study found that SERS and electrochemical sensing modes have linear working curves for miR-106a detection in serum,with the detection limits of 129.72 aM and 1.33 fM,respectively.The dual-mode sensor also shows good recovery rate for sensing miR-106a in serum,which indicates that the sensor is a promising tool for highly sensitive and reliable detection of early cancer.