Magnetic graphene oxide nanocomposite as dual-mode genosensor for ultrasensitive detection of oncogenic microRNA

MicroRNA (miRNA) is a noncoding RNA that controls cellular functions and gene expression. Several oncogenic miRNAs that aberrantly expressed in prostate cancer have the potential to be used as biomarkers. We designed multifunctional nanosheets that can capture, detect, and quantify miRNA 183-5p from prostate cancer cells with the aid of a disposable printed electrode and a portable potentiostat. Magnetic reduced graphene oxide (MrGO) has been used as the starting nanocomposite to analyze miRNA. Three cationic dyes—toluidine blue (TBO), thionine, and neutral red—were used to modify MrGO and evaluate its impact on the electron transfer rate. MrGO modified with TBO had the fastest conductivity and a large electrochemically active surface area. Two strategies were used to detect miRNA. One used peroxidase-labeled amplification and the other used TBO as the redox probe intercalating in the miRNA-capture probe duplex. The intercalator method reduced the complications of using peroxidase-labeled probes and exhibited superior performance. The limits of miRNA detection in human serum and urine were 3.73 and 0.86 aM, respectively, with a linear range from 0.1 nM to over 1 aM. The assay time of the intercalator method, including wash, was less than 16 min, and only one sample droplet (5 μL) was needed for analysis. We provided dual-mode genosensors for miRNA detection, which might be used for point-of-care testing. The incorporation of MrGO, screen-printed carbon electrodes, and portable potentiostat can accelerate biomarker detection, simplify analysis, and reduce the time and cost of analysis.