Piezoelectric olfactory receptor biosensor prepared by aptamer-assisted immobilization

Inspired by the very high sensitivity and specificity of biological olfactory system, engineers pay much attention to biomimetic olfactory biosensors due to their excellent performance and great commercial prospects. In this study we presented an olfactory receptor (OR)-based piezoelectric biosensor with high sensitivity and specificity for the odorant detection, in which aptamers were employed for the specific and effective olfactory receptor immobilization to improve the overall performance of biosensors. An olfactory receptor of C. elegances, ODR-10, was expressed heterologously in HEK-293 cells with a hexahistidine (His6) tag on the N terminus. His6-tagged ODR-10 was extracted from the plasma membrane of transfected HEK-293 cells and used as the sensing element of biosensors. Anti-His6 aptamers were immobilized covalently onto the gold surface of piezoelectric quartz crystal microbalance (QCM) electrode to capture the His6-tagged ODR-10 specifically, as well as achieve the purification of ODR-10 simultaneously. The immobilization procedures were characterized by electrochemical methods and scanning probe microscopy (SPM). Additionally, physical adsorption method was used as a control method to illustrate the influences of immobilization methods on the performances of OR-based biosensors. The results demonstrated that the piezoelectric biosensor prepared by aptamer-assisted immobilization method showed high specificity and improved sensitivity. The detection limit was as low as 1.5 ppm (v/v). Additionally, the aptamer-assisted receptor immobilization method has great potential to become a universal protein immobilization technique in biosensing, and be applied into the development of OR-based biosensor array for the simultaneous detection of several odorants. This aptamer-assisted olfactory receptor biosensor has great application prospects in many fields, such as food safety, environmental monitoring, and disease diagnosis.