Applications Of Several DNA Sensors In The Detection Of MiRNA And Heavy Metal Ions

Due to the fact that DNA sensors have a great variety,smart designed,structurally diverse and high-performing,they have been applied in the field of biological/chemical sensing,bioimaging,diagnosis and treatment of diseases and so on.Based on the comprehensive introduction of types,excellent properties and widespread applications of DNA sensors,we further developed multielement DNA sensors with high sensitivity and selectivity for detecting miRNA and heavy metal ions and enriching the applications of DNA sensors.The specific research contents are as follows:(1)A simple and enzyme-free DNA sensor was designed for highly sensitive and selective detection of miR-21 based on multiple signal amplification strategy.This DNA sensor was composed of six hairpins(H1-H6),in which H1 and H2 participated in catalyzed hairpin assembly(CHA),and H3-H6 participated in hybridization chain reaction(HCR).Due to intramolecular hybridization,all hairpins were metastable in the buffer solution.In the presence of target miR-21,the hairpin reactants were opened and hybridized with corresponding complementary DNA strand via toehold-mediated CHA and HCR reaction,resulting in hugely amplifying signal output.A linear response range of miR-21 from 25 p M to 1 n M with a LOD of 1.8 p M was obtained.Without introduce of external protein enzymes,this sensing system showed high sensitivity and selectivity towards the target miR-21 in vitro detection and was successfully applied to detection miR-21 in human serum samples.(2)A near-infrared light excited UCNP-DNAzyme nanosensor was constructed.In this nanosensor,Na YF₄:Yb,Er UCNP were introduced as the donor of luminescence resonance energy transfer(LRET),DNAzyme-functionalized black hole quencher 1(BHQ1)acted as energy transfer acceptor.Taking advantage of reaction between an amino group modified on the end of DNAzyme and a carboxyl group modified on the surface of UCNP,we successfully modified UCNP with DNAzyme,which were characterized by FT-IR,UV-Vis absorption spectrum and Zeta potential.In the process of modified with DNAzyme,we discovered that the method of DNA firstly hybridized with each other and then modified on the surface of UCNP together was more efficient.UCNP-DNAzyme nanosensor has small size and good stability,which may show practical applications prospect in biological system.(3)Near-infrared light excited UCNP-DNAzyme nanosensor was successfully applied to Pb²⁺detection and its imaging in living cells and early-stage zebrafish.In the presence of Pb²⁺,the DNAzyme was activated and cleaved the substrate strand into two fragments,resulting in the rupture of substrate strand and the recovery of luminescence.Based on this principle,we have successfully detected Pb²⁺in vitro.A linear response range from 0.1 n M to 10 n M was obtained.Meanwhile,by virtue of unique spectroscopic properties of UCNP like high tissue penetration depth,negligible autofluorescence and good photostability,this sensing strategy was successfully applied in the imaging of Pb²⁺in living cells and early-stage zebrafish.