A Study On The Application Of DNA Nanostructures In Highly Efficient Surface-enhanced Raman Bioanalysis

Surface-enhanced Raman scattering(SERS)is that significantly enhances the Raman scattering of molecules adsorbed on rough metal surfaces.The main contribution to the SERS effect comes from the enhancement of the electromagnetic field due to localized surface plasmon resonance in metals.Gold and silver nanomaterials are widely used as SERS substrate materials because of the surface plasmon resonance effect generated by photoexcitation that can significantly enhance the SERS signal.However,the fine nanostructures,surface roughness and aggregation of such materials cannot be precisely controlled in practical applications,resulting in poor SERS detection stability and repeatability.Therefore,researchers often calibrate errors caused by uncontrollable factors such as sample interference and signal fluctuations in the measurement conditions by introducing internal standards or using ratiometric methods.Alternatively,the arrangement of nanomaterials is fundamentally improved,for example,by driving the top-down spontaneous assembly of nanoparticles into a single-level ordered structure at the interface of two incompatible phases owing to the reduction of interfacial energy.It is shown that the homogeneity of nanoparticle arrays at the liquid-phase interface is much better than random aggregation of particles in nanoparticle sols or fixed arrays on solid surfaces.With the advantages of specific recognition,flexible modification of functional groups at the ends and reversible binding,DNA can not only flexibly adjust the gap between SERS substrate nanoparticles to enhance the SERS signal of the target molecule,but it can also use the nucleic acid signal amplification technique of DNA structure to further reduce the detection limit of the target.In recent years,biosensors based on the combination of DNA structures and SERS technology have been widely used for the quantitative detection of a variety of biomolecules.Therefore,in order to improve the stability and reproducibility of SERS biodetection,this study combines SERS technology with DNA structure to construct a SERS sensing platform with outstanding SERS enhancement effect,signal stability,and can achieve efficient and sensitive detection of biomolecules.1.Adenosine triphosphate responsive metal–organic frameworks equipped with a DNA structure lock for construction of a ratiometric SERS biosensorIn this work,a novel ratiometric SERS biosensor is constructed based on stimuli-responsive DNA functionalized MOFs for detection of adenosine triphosphate(ATP).Firstly,MOFs with high porosity and excellent biocompatibility are employed to encapsulate toluidine blue(TB)in the micropores which are blocked by DNA structure.Subsequently,in the presence of target ATP,the DNA structure is disintegrated to form the ATP-aptamer complexes for releasing TB and complementary DNA(c DNA).Then the solution containing TB and c DNA is added on the gold nanoflowers(GNFs)modified with hairpin DNA(H1).Nextly,c DNA complemented with H1 labeled by Cy5 to form the rigid double-stranded DNA(ds DNA),making Cy5 away from GNFs substrate to decrease the SERS signal of Cy5.At the same time,TB can be adsorbed on the GNFs to insert the ds DNA formed by c DNA and H1 for increasing the SERS signal.Thus,a ratiometric SERS biosensor is fabricated,which can enhance the reliability of SERS analysis than that of single signal.As a result,the detection range of ATP is 1nmol/L to 200 nmol/L with detection limit(LOD)of 0.4 nmol/L.This new ratiometric SERS strategy shows good performance for detection of ATP,which may have potential for detection of other biomoleculars or metal ions.2.DNA structure stabilized liquid-liquid self-assembly ordered Au nanoparticles interface for sensitive detection of mi RNA 155In this study,we synthesized a DNA structure-functionalized gold nanoparticles(Au NPs)self-assembled at the cyclohexane-water interface as a large-area SERS active material and combined it with a nucleic acid amplification strategy assisted by exonuclease Ⅲ(exo Ⅲ)to construct a liquid-phase SERS biosensor for the mi RNA 155 was detected by a liquid-phase SERS biosensor with high efficiency and sensitivity.The target mi RNA 155 releases the trigger strand S2 by strand replacement,and then exo Ⅲacts on the hybrid of S2 and DNA Y-junction structure to engage S2 in multiple nucleic acid cycle amplification process and release a large number of single-stranded S6 labeled with Raman molecular methylene blue(MB).The SERS sensing platform is prepared using the interface assembled with Au NPs with two different DNA single strands(S7 and S8)stabilized by S6 modification.Compared with Au NPs assembled randomly at the two-phase interface,the DNA-stabilized Au NPs self-assembled at the interface prepared in this study had more uniform nanogaps,more pronounced collective properties,and significantly enhanced SERS signals.Finally,the LOD of this liquid-phase SERS biosensor for mi RNA 155 was calculated to be 1.45 fmol/L,and it also has a very wide linear range(100 fmol/L-5 nmol/L).Therefore this SERS sensing platform has great potential for the detection of mi RNAs in early cancer cells.3.Construction of liquid-phase enzyme-free SERS biosensor based on DNA technology for ultra-sensitive detection of mi RNA155In this study,we report a liquid-phase SERS biosensor based on entropy-driven nucleic acid amplification reaction and self-assembly interface of Au@Ag@Au composite nanomaterials with functionalized DNA structures self-assembled interface of Au@Ag@Au composite nanomaterials for ultrasensitive detection of mi RNA 155.The DNA-assembled nanoparticle interface exhibits very strong stability performance,which greatly reduces the degree of splitting and breaking of the nanoparticle assembly interface,prepares a large area of well-arranged assembly interface,and improves the reliability of SERS quantitative detection.The SERS biosensor is calculated to have a LOD of 2 amol/L for mi RNA 155 and an outstanding detection range from 0.1 fmol/L to5 nmol/L.Thus,the SERS biosensor we designed exhibits excellent quantitative analysis performance for mi RNA,providing a convenient and reliable detection method for monitoring mi RNA in tumor and cancer cells.