The possibility to diagnose and monitor diseases, and in particular some cancers, by measuring the concentration of volatile markers in body fluids (or in the breath) has gained acceptance in recent years. For this purpose it is necessary the development of new electronic noses with extremely low detection limits, high odour specificity and an unmatched chemical space, thus having the potential to reach the medical diagnostic application targets. Bioelectronic noses based on the response of biological olfactory receptors could satisfy these requirements thus constituting a unique emerging technology onto which to base these challenging diagnostics noses.
Our research group is part of a European collaboration (SPOT-NOSED) aiming to develop a nanobiosensor array based on the electrical properties of single ORs, to mimic the performances of natural olfactory sensing system. The individual OR conformational changes upon odorant ligand binding is detected by monitoring the impedance of the receptor. To sense the tiny electrical signals available from the olfactory receptors in the physiological medium (necessary to keep the functionality of the receptors), a high-sensitivity (low noise) instrument has been developed specifically for Electrochemical Impedance Spectroscopy (EIS) at the nanoscale.
The first experimental evidence of the sensitive action of olfactory receptors immobilized onto an inorganic substrate has been performed using both rat I7 (OR I7) and human 17-40 (cmyc-OR 17-40) olfactory receptors. The olfactory receptors have been expressed in yeast cells and deposited on the gold substrate in membrane fraction form. The olfactory receptor response upon odorant stimulation with respect to specific and non-specific odorants has been verified by using EIS and Surface Plasmon Resonance.
Present results open the possibility to develop a completely new generation of bioelectronic devices for the assessment of odorants constituting a signature of metabolic states/diseases, associated with drugs/explosives/pollutants, participating in food aromas. Ligand screening for orphan receptors and pharmacological studies may constitute further high value applications.