Electrode surface nanostructuring via nanoparticle electronucleation for signal enhancement in electrochemical genosensors

Biosensor read out signals can be enhanced by carefully designing the transducer surfaces to achieve an optimal interaction between the recognition elements immobilised and the targeted analyte. This is particularly evident in the case of genosensors, where spacing and orientation of immobilised DNA capture probes need to be controlled to maximise subsequent surface hybridisation with the target sequence and achieve high binding signals. Addressing this goal, we present a novel approach based on the surface nanostructuring of glassy carbon electrodes (GCEs) towards the development of highly sensitive electrochemical genosensors. Gold nanoparticles were sequentially electrochemically nucleated on glassy carbon electrodes to form dense arrays of randomly distributed gold nanodomains. The number density of the electronucleated nanoparticles could be increased by repeatedly alternating between a short electronucleation step and the subsequent insulation of the nucleated nanoparticles with thiolated DNA probes. This approach allowed for the creation of highly structured surfaces whilst preventing aggregation of nanoparticles. The performances of planar gold electrodes and that of the nanopatterned surfaces prepared following several rounds of deposition were compared for the amperometric detection of DNA. Three rounds of deposition exhibited the highest sensitivity (44.89 nA × nM−1), with a dynamic detection range spanning from 0.53 nM to 25 nM of the targeted sequence, i.e. one order of magnitude lower than that obtained for the planar gold electrodes. The use of the nanostructured surface we report here may find application not only in DNA biosensors but also for any sensing application requiring highly sensitive measurements.