Evaluating Insect Odorant Receptor Display Formats for Biosensing Using Graphene Field Effect Transistors

Graphene field effect transistor (GFET) biosensors have been used to evaluate insect odorant receptor (OR) display formats and the effect of the presence of the Orco subunit on in vitro sensing using OR subunits. The biosensors were fabricated by immobilizing the OR nanodiscs and OR ± Orco liposomes onto GFET devices. Two ORs from Drosophila melanogaster (DmelOR10a and DmelOR22a) were used in this study. We demonstrated that both DmelOR10a and DmelOR22a in nanodiscs and OR ± Orco liposomes showed a selective electrical response to their respective positive ligands, methyl salicylate and methyl hexanoate. The OR nanodisc sensors produced the strongest sensing signal with a limit of detection of 1 fm. We also found that the upper detection limit was increased, and the sensitivity of the Orco coexpressed liposome sensors was enhanced by approximately an order of magnitude when compared to the OR liposome sensors.