Insect odorant receptor nanodiscs for sensitive and specific electrochemical detection of odorant compounds

An electrochemical sensing methodology using an insect odorant receptor (iOR) as the biological recognition element for detection of odorant compounds is presented. Or22a from the fruit fly Drosophila melanogaster (DmOr22a) was used as a model receptor for the study. DmOr22a in phospholipid nanodisc preparations was shown to be functionally active toward its known ligand (ethyl hexanoate), as measured by electrochemical impedance spectroscopy (EIS). iOR nanodiscs covalently immobilized on a gold substrate were further characterized by atomic force microscopy (AFM), quartz crystal microbalance with dissipation monitoring (QCM-D) and neutron reflectometry in order to study surface modification and understand the underlying mechanisms associated with ligand binding. The EIS sensor exhibited high sensitivity and specificity towards ethyl hexanoate with a detection limit of 5.5 fM. Neutron reflectometry studies provided evidence to support conformational changes in the receptor upon ligand binding. The EIS based detection strategy provides a facile, sensitive and fast method for detecting odorant compounds and paves the way for further development of odorant biosensors.

Automated summary

This study presents an electrochemical sensing methodology using an insect odorant receptor (iOR) as the biological recognition element for detection of odorant compounds. The fruit fly Drosophila melanogaster's Or22a was used as a model receptor and shown to be functionally active towards its known ligand (ethyl hexanoate). The EIS sensor exhibited high sensitivity and specificity towards ethyl hexanoate with a detection limit of 5.5 fM, with neutron reflectometry studies providing evidence of conformational changes in the receptor upon ligand binding.