Nanogap-based enzymatic-free electrochemical detection of glucose

Although non-enzymatic glucose sensors have demonstrated better stability and reproducibility with respect to enzymatic ones, so far they have been inappropriate for most applications, since they require alkaline conditions to achieve the necessary sensitivity. In this work, we propose a gold nanogap-based non-enzymatic sensor to localize the generation of alkaline conditions inside the gap, thus preserving the overall pH in the media during glucose detection. The working principle is based on an electrochemical bi-potentiostatic measurement, where an alkaline aqueous condition is locally generated at one side of nanogap, while glucose detection is performed at the counterpart. To this purpose, a nanogap array platform was fabricated by means of standard lithography and controlled electromigration. Mono-potentiostatic electrochemical detection of ascorbic acid was successfully performed to preliminary test the platform prior to measuring glucose in bi-potentiostatic mode. Cyclic voltammetries reveal that two oxidation peaks are sensitive to glucose concentration, making nanogap glucose detection possible in principle. This promising proof of concept could be innovative in bio-applications with implantable devices or direct monitoring of cell culture, where neutral pH in contact with living tissue is required. Further geometrical improvements of the system to increase the durability of the sensor are currently still in progress, and are briefly discussed in the final part of the paper.