Fabrication of a quinone containing layer on gold nanoparticles directed to a label-free and reagentless electrochemical miRNA sensor

Abstract

In this work, we report a simple electrochemical method to fabricate a label-free and reagentless electrochemical sensor for microRNA detection based on self-assembly of a multifunctional layer on gold nanoparticles-modified glassy carbon electrodes (AuNPs/GCEs). The self-assembled monolayer (SAM) is made of a mixture of 5-hydroxy-3-hexanedithiol-1,4-naphthoquinone (JUG-SH), which plays the role of a transducing element, and of 6-mercaptohexanoic acid (6-MHA). The carboxylic group of 6-MHA is used as an anchoring site for grafting DNA-NH₂ probes and the quinone group as an immobilized redox group for probing biomolecular interactions. Hybridization with a perfect base pairing at the SAM/solution interface generates a current increase named “signal-on” that can be recorded simply by square wave voltammetry (SWV) in a phosphate buffer at very low potentials (between 0 and −1 V vs. the SCE). The sensor is selective and highly sensitive, with a detection limit of ca. 100 fM.