Development of novel nanomaterials for biosensors has intrigued widespread interest. Here, we report a method to graft the redox-active dye Methylene Blue (MB) onto molybdenum disulfide (MoS2) nanosheet surface via electrostatic and π-stacking interaction. The adsorption of MB on nanosheets was investigated by atomic force microscopy (AFM), which proved that the adsorption isotherm fits a Temkin not a Langmuir model. After studying the electrochemical properties of MB-decorated MoS2 nanocomposite (MoS2@MB) on a glassy carbon electrode (GCE), an electrochemical sensor for microRNA-21 detection was designed. The modified GCE can quantify microRNA-21 in concentrations as low as 68 fM, typically at a working potential of -0.28 V (vs. SCE). The same modified electrode also shows outstanding electrocatalytic ability towards individual and simultaneous determination of dopamine (DA) and uric acid (UA) with electrochemical peaks at 0.16 V (DA) and 0.45 V (UA). The detection limits for simultaneous determination are 0.58 μM for DA and 0.91 μM for UA, respectively. Graphical abstract A powerful sensing electrode was obtained by grafting Methylene Blue (MB) on molybdenum disulfide (MoS2@MB) nanosheet surface. Such MoS2@MB-based electrochemical sensor was used to label-free detect microRNA and simultaneously determine dopamine and uric acid.
Keywords: Dopamine; Label-free; Methylene blue; MicroRNA-21; Molybdenum disulfide; Sensing material; Uric acid.