Study On Ultrasensitive Electrochemical Biosensor For MiRNA Based On Duplex Specific Nuclease

As a class of biomarkers that assist cancer diagnosis,the development of highly sensitive and selective detection methods for miRNA is essential.In this work,we have combined the advantages of duplex specific nuclease and nanomaterials to construct two methods for ultrasensitive detection of miRNA.The detailed researches are as follows.1.A miRNA electrochemial biosensor based on duplex specific nuclease and bridge DNA-gold nanoparticlesMultifunctional gold nanoparticles(AuNPs)are firstly prepared by mixing AuNPs with two thiolated DNA(DNA probe 1 and 2)via gold-sulfur chemistry.Next,by the hybridization of two partially complementary sequences(bridge DNA probe 1 and 2),bridge DNA is formed with a double-stranded middle section and four single-stranded tails.Two are designed to hybridize with DNA probe 1 and one is designed to hybridize with DNA probe 2.In addition,the last single-stranded tail is left for further electrode localization.Therefore,the bridge DNA links three AuNPs specially to form the DNA nanocomposites.For the fabrication of the electrochemical miRNA biosensor,the gold working electrode is immobilized with thiolated capture probe.The hairpin structure of the DNA probe is "inactivated" to capture bridge DNA-AuNPs.However,after the introduction of target miRNA,the hairpin is opened and the formed DNA/RNA duplex can be recognized by DSN,which digests DNA in the duplex.The remained DNA sequence is "activated",which hybridizes with the fourth single-stranded end of bridge DNA to localize the DNA nanocomposites.Meanwhile,miRNA is released,which triggers more cycles of capture probe activation and bridge DNA-AuNPs localization events.Significant electrochemical response can be obtained to indicate the initial level of miRNA2.A miRNA electrochemial biosensor based on duplex specific nuclease and DNA functionalized porous magnetic nanoparticlesThe biofuel cell(BFC)system is composed of indium tin oxide cathode and graphene oxide/gold nanoparticles/glucose oxidase anode.Redox probe of[Fe(CN)6]3-is entrapped inside porous Fe3O4 nanoparticles by DNA.However,in the presence of target miRNA,hybridization reaction occurs between miRNA and DNA,which initiates the release of[Fe(CN)6]3-.Moreover,duplex specific nuclease is further employed to trigger target recycling amplification.As a result,much more redox probes are released and the open circuit voltage is significantly increased.