Detection of odorant molecules via surface acoustic wave biosensor array based on odorant-binding proteins

In this paper, we present an array of biosensors for vapour phase detection of odorant molecules based on surface acoustic wave (SAW) resonators coated with odorant-binding proteins (OBPs). For the first time, the sensing capabilities of three different OBPs, as sensitive layers for SAW devices, are studied and compared. The SAW biosensor array is composed of three SAW devices coated by the droplet method with the wild-type OBP from cow (wtbOBP), a double mutant of the OBP from cow (dmbOBP) and the wild-type OBP from pig (wtpOBP). An uncoated device is used to compensate the variations of the environmental parameters. The SAW devices consist of two-port resonators fabricated on quartz (ST-cut, x propagation) with electrodes made of aluminium covered with a thin gold film (2 nm thick). The obtained surface densities of OBP layers are between 1.18×10-6 kg/m2 and 2.31×10-6 kg/m2 and were calculated measuring the resonant frequency shift of the SAW devices after the coating. The SAW biosensor array was tested in nitrogen upon exposure to vapours of R-(-)-1-octen-3-ol (octenol), in the range of concentration between 13 and 61 ppm, and R-(-)-carvone (carvone), in the range between 9 and 80 ppm. The highest sensitivity for detection of octenol (25.9 Hz/ppm) was obtained using the wtpOBP-based SAW biosensor, while the highest sensitivity for detection of carvone (9.2 Hz/ppm) was obtained using the dmbOBP-based SAW biosensor.