Biosensing with insect odorant receptor nanodiscs and carbon nanotube field effect transistors.

Insect odorant receptors (ORs) have been reconstituted into lipid nanodiscs and tethered to carbon nanotube field effect transistors to function as a biosensor. Here four different insect ORs from D. melanogaster (DmelOR10a, DmelOR22a, DmelOR35a, and DmelOR71a) were expressed in Sf9 cells, purified and reconstituted into lipid nanodiscs. We have demonstrated that each of these ORs produce a selective and highly sensitive electrical response to their respective positive ligands, methyl salicylate, methyl hexanoate, trans-2-hexen-1-al and 4-ethylguaiacol, with limits of detection in the low fM range. No detection was observed for each OR against control ligands, and empty nanodiscs showed no specific sensor signal for any of the odorant molecules. Our results are the first evidence that the insect ORs can be integrated into lipid nanodiscs and used as primary sensing elements for bioelectronic nose technologies.