Enzyme catalytic amplification of miRNA-155 detection with graphene quantum dot-based electrochemical biosensor

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 (NH 2 -DNA). After the construction of the double-stranded DNA structure, the activated carboxyl groups of graphene quantum dots (GQDs) assembled on NH 2 -DNA. GQDs were used as a new platform for HRP immobilization through noncovalent assembly. HRP modified biosensor can effectively catalyze the hydrogen peroxide (H 2 O 2 )-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.