DNA Mediated Self-assembly Nanostructures For Metal Ions And MicroRNAs Quantitative Detection In Situ

DNA driven self-assembled nanostructures have attracted a lot of attentions in recent years due to its specific physical,chemical,morphological and optical properties.In this paper,two dimensional homogeneous and three dimensional heterogeneous nanostructures were constructed based on DNA complementary technology.Inspired by the multifunctional properties and flexibility and programmability of DNA frame of self-assembly nanostructures,series of detection methods with high sensitivity and selectivity were established with self-assembled nanostructures through conformational optical change caused by the transformation of nanostructures.First,plasmonic trimers were constructed using gold nanoparticles?Au NPs?.Through the coating different kinds of Raman label on the individual nanoparticles in the trimer,and inserting the recognition sequence for Ag⁺and Hg²⁺in the DNA frame,the plasmonic trimers can cause conformational change in the presence of target ions,which will cause different Raman response.Upon this mechanism,simultaneous detection method for Ag⁺and Hg²⁺were set up for the first time with ultralow limited of detection?LOD?values.Second,three dimensional nanopyramids were fabricated with two Au NPs and two upconversion nanoparticles?UCNPs?under the complementary interaciton of DNA sequences.The Au-UCNP pyramids displayed dual optical activities,strong circular dichroism and significant luminescence,which could be used for monitoring microRNA.CD intensity will decrease while the luminescence intensity increases in the presence of microRNA.The experimental results show that the CD intensity had an outstanding linear range from 0.073 to43.65 fmol/10?g_RNA and a limit of detection?LOD?of 0.03 fmol/10?g_RNA,whereas the luminescence intensity ranged from 0.16 to 43.65 fmol/10?g_RNA with a LOD of 0.12fmol/10?g_RNA.And the results indicated that CD signal is much more sensitive than the luminescent signal at the same detect conditions.Third,silver sulfide nanoparticles?Ag₂S NPs?,UCNPs,and Au-Cu₉S₅ NPs were first prepared.And then,heterogeneous nanopyramids were constructed with two silver sulfide nanoparticles?Ag₂S NPs?,one UCNPs,and one Au-Cu₉S₅ NPs using DNA sequences.The nanopyramids owned multifunctional properties,which exhibit fluorescence at visible?541 nm?and near-infrared region?NIR-II,1227 nm?when excited by 808 nm laser and could be further used for dual microRNA detection.Moreover,the nanopyramids also exhibited photothermal ability due to Au-Cu₉S₅ NPs when excited by 980 nm laser.Fourth,dual microRNAs detection strategy was set up for living cells based on the constructed heterogeneous nanopyramids,which could quantify the intracellular amounts of microRNA-203^b and microRNA-21.The upconversion luminescence has a linear relationship with miR-203^b from 0.13 to 54.54 fmol per 10?g_RNA and a limit of detection?LOD?of 0.09fmol per 10?g_RNA,whereas the Ag₂S NP luminescence has a linear relationship with miR-21from 0.37 to 43.56 fmol per 10?g _RNA,with a LOD of 0.23 fmol per 10?g _RNA.Significantly,the nanopyramids can be successfully used for miRs-responsive bioimaging in a tumor-bearing animal model.Furthermore,the pyramids could eliminate tumors in vivo completely taking advantage of the photothermal capabilities.