Detection Of MicroRNA In Exosomes Based On SERS And Single Molecule Fluorescence

Exosomal microRNA(miRNA)has a tumor-specific expression profile and plays an important role in tumor occurrence and progression.Detecting the expression level of miRNA in exosomes can provide a key basis for tumor diagnosis and treatment.The work of this thesis aims to develop exosomal miRNA detection technology with high sensitivity,good reliability and strong applicability.We used functionalized nanoprobes to establish optical detection method of miRNA-21(miR-21)based on surface enhanced Raman scattering(SERS)and single molecule fluorescence(SMF).We successfully realized the quantitative detection of miRNA-21.The work of this thesis can provide an effective strategy for the early clinical diagnosis of cancer.The main results of the thesis include:(1)In order to explore the technical advantages of the combined use of SERS and SMF,a new type of SERS-surface enhanced fluorescence(SEF)-SMF triple-mode optical nanoprobe was designed and prepared.The probe used gold-core silver-shell nanorods as the metal substrate,which were modified with Raman molecules and fluorescent molecules.The SEF enhancement effect of the nanoprobe was controlled by the number of polymer electrolyte layers coated on the particle surface.Using this probe,SERS-fluorescence and super-resolution triple mode optical imaging of cancer cells were acquired.The results showed that the combination of SERS and SMF can obtain richer optical information.(2)According to the requirements and characteristics of exosomal miRNA detection,a miRNA nano-optical probe was designed based on SERS and SMF.The probe used spherical gold-core silver-shell nanoparticles as the metal substrate.The integration of SERS and SMF signals was achieved by modifying Raman molecules and fluorescent DNA strands on the nanoparticles.The probe has the advantages of small size,simple structure,high stability and dual-mode optical signal,indicating that it should be an excellent miRNA detection probe.(3)A miR-21 detection scheme combining SERS and SMF is proposed,which used the miRNA probes to identify and hybridize the miR-21 sequence.The quantitative detection of miR-21 was achieved by detecting the SERS signal and SMF signal at the hybridization reaction sites.The detection limit is 3p M and the linear dynamic response range is0.01 n M-1μM.This strategy has many advantages such as simple operation,strong applicability,high sensitivity,strong reliability and wide dynamic range,which holds great potential in miRNA detection.