▎ 摘　　要

A specific and sensitive method was developed for quantitative detection of miRNA by integrating horseradish peroxidase (HRP)-assisted catalytic reaction with a simple electrochemical RNA biosensor. The electrochemical biosensor was constructed by a double-stranded DNA structure. The structure was formed by the hybridization of thiol-tethered oligodeoxynucleotide probes (capture DNA), assembled on the gold electrode surface, with target DNA and aminated indicator probe (NH2-DNA). After the construction of the double-stranded DNA structure, the activated carboxyl groups of graphene quantum dots (GQDs) assembled on NH2-DNA. GQDs were used as a new platform for HRP immobilization through noncovalent assembly. HRP modified biosensor can effectively catalyze the hydrogen peroxide (H2O2)mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), accompanied by a change from colorless to blue in solution color and an increased electrochemical current signal. Due to GQDs and enzyme catalysis, the proposed biosensor could sensitively detect miRNA-155 from 1 fM to 100 pM with a detection limit of 0.14 fM. High performance of the biosensor is attributed to the large surface-to-volume ratio, excellent compatibility of GQDs. For these advantages, the proposed method holds great potential for analysis of other interesting tumor makers. (C) 2015 Elsevier B.V. All rights reserved.