Research On Colorimetric Sensor For MiRNA Detection Based On Peroxidase-like Activity Of Graphene/Gold-nanoparticles Hybrids

MicroRNA (miRNA) is a class of non-coding small RNA, which plays vital regulatory role in the life activities of onto genetic biological differentiation. There is characteristic of miRNA which could specifically express in cancer and other serious diseases. MiRNA is a potential biological indicator which could evaluate the genotoxicity of contaminant. Therefore, the detection of miRNA is very important. The current widely used standard methods for miRNA analysis are Northern blotting, real-time PCR, and microarrays. These methods are complicated, time-consuming, money-consuming, but acquire low sensitivity, poor reproducibility and inaccuracy. Thus, it is urgent to develop new colorimetric platforms with easy design, high response, high stability and easy probe preparation for specific miRNA detections.In this work, a visible and label-free colorimetric sensor for miRNA detection was developed based on the peroxidase-like activity of graphene/gold-nanoparticles (Au-NPs) hybrids which could be flexibly controlled by Peptide Nucleic Acid (PNA). The spontaneous absorption of ssPNA on graphene/Au-NPs hybrids surface causes the peroxidase-like catalytic activity of hybrids to be almost completely deactivated via n-n stacking interaction between ssPNA and graphene, so that TMB could not be oxidized to oxTMB, leading to no color change. The addition of different concentration of miRNA triggered hybridization reaction between the PNA probe and miRNA, leading to forming double-chain structure (PNA/miRNA). The impairment of the ?-? stacking interaction between double-chain structure and graphene could lead to the release of PNA/miRNA duplexes from the hybrids surface, which would restore the catalytic activity of hybrids with a concomitant colorless-to-blue color change. Therefore, the produced color change could be employed to realize the visible and quantitative detection of target miRNA.As a result, this sensor exhibited low background signal and responded linearly to miRNA-21 from 10 nM to 0.98 ?M with a detection limit of 3.2 nM (S/N=3) under the optimal conditions. The detection limit is comparable and even better than the reported lable-free colorimetric method for miRNA, suggesting its sensitivity. Furthermore, a relative standard deviation of 3.7% (n=3) was obtained for this method, indicating the good reproducibility of this colorimetric method. In contrast to miRNA-21, the low response of this strategy to interference miRNA (miRNA-125b and miRNA-29a) under the same conditions, which could ensure its good specificity. In addition, the biosensor could be also extended to miRNA-21 detection in human serum and miRNA mixture system. Therefore, this colorimetric sensor platform is a potential alternative assay for miRNA detection in biomedical research.