Hybrid organic/inorganic interfaces as reversible label-free platform for direct monitoring of biochemical interactions

•Hybrid organic-inorganic functional layer to monitor biospecific interactions.•Reversible label-free glutathione-S-transferase (GST) biosensor.•Four orders of magnitude wide detectable GST concentration.•Low detectable GST concentration (200 pmol L−1).

The combination of organic and inorganic materials to create hybrid nanostructures is an effective approach to develop label-free platforms for biosensing as well as to overcome eventual leakage current-related problems in capacitive sensors operating in liquid. In this work, we combine an ultra-thin high-k dielectric layer (Al2O3) with a nanostructured organic functional tail to create a platform capable of monitoring biospecific interactions directly in liquid at very low analyte concentrations. As a proof of concept, a reversible label-free glutathione-S-transferase (GST) biosensor is demonstrated. The sensor can quantify the GST enzyme concentration through its biospecific interaction with tripeptide reduced glutathione (GSH) bioreceptor directly immobilized on the dielectric surface. The enzymatic reaction is monitored by electrical impedance measurements, evaluating variations on the overall capacitance values according to the GST concentration. The biosensor surface can be easily regenerated, allowing the detection of GST with the very same device. The biosensor shows a linear response in the range of 200 pmol L−1 to 2 µmol L−1, the largest reported in the literature along with the lowest detectable GST concentration (200 pmol L−1) for GST label-free sensors. Such a nanostructured hybrid organic-inorganic system represents a powerful tool for the monitoring of biochemical reactions, such as protein-protein interactions, for biosensing and biotechnological applications.