| With the in-depth study of modern medicine and biology,people have gradually realized that miRNAs are closely related to the processes of cell proliferation and differentiation.In early tumor cells,miRNAs show short sequence,high similarity,low expression abundance,and easy degradation.Conventional detection techniques are difficult to meet the detection requirements.With the rapid development of nanotechnology,the modification of different probe molecules on nanomaterials of different compositions,different sizes,and different morphologies,and the construction of biosensing platforms for nucleic acid,protein,etc.analysis and detection have made great progress.Researchers use gold nanoparticles to produce localized surface plasmon resonance(LSPR)effects and build nanoparticle assemblies through covalent bonds or intermolecular interactions so that the microscopic local electromagnetic field strength between nanoparticles is caused by surface plasmon resonance coupling.It is greatly enhanced,thereby forming a large number of active "hot spots" required for SERS signal enhancement,increasing the scattering intensity of SERS signal molecules in the hot spot area,and realizing high-sensitivity detection of biologically related targets.At present,the construction of active "hot spots" with Raman signal enhancement effect is mostly random assembly and not controllable.In addition,the construction of some SERS biosensors is based on the aggregation of nanoparticles in solution,and there may be other interference factors(such as pH value).,Salt concentration,etc.)caused by uncontrollable aggregation and false-positive signals.Therefore,directly constructing a DNA-mediated in-situ DNAmediated sensing platform with high SERS signal response and a controllable sensor platform with high SERS signal response has become our research goal.It is expected to provide a new solution to achieve high-sensitivity detection and analysis of miRNA.The main research contents of this paper are as follows:(1)By introducing the "catalytic hairpin self-assembly" target cyclic signal amplification technology,the target is designed to trigger the assembly of two hairpin DNA strands and the assembly of the corresponding Au Coresatellite nanostructures.Calculate the thermodynamic parameters of the selected DNA sequence by NUPACK.Design two different hairpin DNAs(HP1 and HP2).When the target sequence is present,the target can be paired with the pre-designed sticky end to open the stem of the clip HP1,thereby further triggering the complementary hybridization of HP 1/HP2,leading to the target The target is released and used to trigger the next cycle of opening HP1.The result of the cycle will produce a large number of HP1/HP2 double strands,which can be used to guide the subsequent assembly of Au Core-satellite nanostructures.Since the migration rate of different DNA sequences in polyacrylamide gel electrophoresis is affected by their sequence length and spatial structure,in addition,the fluorescence intensity of DNA bands is directly related to their content.Therefore,we used the results of gel electrophoresis imaging to verify The feasibility of the designed experiment.(2)By using two hairpin DNAs as the connecting medium to modify the surface of Au nanoparticles of two sizes respectively,a self-assembled"Core-satellite" nanostructure with the enhanced local electromagnetic field is constructed in situ on a two-dimensional substrate.It forms many active "hot spots" enhanced by the electromagnetic field generated by the strong coupling plasmon resonance effect to construct a surface-enhanced Raman(SERS)sensing platform with controllable "hot spots" and high sensitivity.The controllable assembly of "Core-satellite" nanostructures is regulated by the specific recognition of the target to be tested in the catalyzed hairpin selfassembly(CHA)cycle amplification strategy,thereby regulating the "hot spots"and the changes of the corresponding SERS signals,and realizing the detection of nucleic acids Highly sensitive detection. |
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