Hyaluronic acid functionalized nanostructured sensing interface for voltammetric determination of microRNA in biological media with ultra-high sensitivity and ultra-low fouling

An electrochemical biosensor for the detection of microRNA was prepared via chemical grafting of a Methylene Blue labeled reporter (MB-Rep) duplex onto a nanostructured surface that was obtained by electrodeposition of cobalt oxide and poly(o-phenylenediamine). This is followed by the attachment of hyaluronic acid and gold nanoclusters. In the presence of the target (microRNA), the probe-target duplex and the MB-Rep hairpin are formed. These will displace the labeled reporter from the sensor surface, and this results in a decrease of the amperometric signal for MB at a typical working voltage of -0.28 V (vs. Ag/AgCl). The electrode modified with hyaluronic acid possesses a large electroactive surface area and an excellent antifouling property. This makes it useful for ultrasensitive quantitation of microRNA even in complex biological media. The sensor has a linear response in the 100 f. to 0.1 mu MmicroRNA concentration range, and a 33.3 f. detection limit. It was successfully applied to the determination of microRNA in cancer cells.