Piezoelectric biosensor using olfactory receptor protein expressed in Escherichia coli.

An olfactory receptor protein of C. elegans, ODR-10, was expressed in Escherichia coli as a fusion protein, with GST and 6x His-tag. The expression of the target protein was analyzed by SDS-PAGE and Western blot, and was confirmed to be expressed at the membrane fraction of the host E. coli. The surface of a quartz crystal microbalance (QCM) was coated with crude membrane extracts, containing the expressed receptor protein, and the interaction between the olfactory receptor and various odorant molecules examined. Compared with other odorants, diacetyl (2,3-butanedione), known as a natural ligand for the ODR-10 receptor, interacted most strongly with the expressed protein. Various concentrations of diacetyl were applied to the expressed ODR-10 receptor, and the response of the QCM showed a linear relationship to the logarithmic value of the odorant concentration. This piezoelectric biosensor system, using olfactory receptor proteins expressed in E. coli, can be used in diagnostics, toxic chemical detection and the quality control of food.