A molybdenum disulfide@Methylene Blue nanohybrid for electrochemical determination of microRNA-21, dopamine and uric acid

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.

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