A piezoelectric biosensor as an olfactory receptor for odour detection: electronic nose

Humans can detect and differentiate the presence of different odours even a t trace levels of these odorous compounds. The odour quantification of any particular samples is normally based on conventional panel decisions. Other analytical instruments could be used to detect trace levels of odorous mol ecules. This study presents the results of a biological sensor system subje ct to different odorants. The system consists of a sensor in which the isol ated olfactory receptor proteins (ORPs) from bullfrogs (Rana spp.) were coa ted onto the surface of a piezoelectric (PZ) electrode, similar to the mech anism of human olfaction. The PZ crystal served as a signal transducer. The results indicate rapid (about 400 s), reversible, and longterm (up to 3 mo nths) stable responses to different volatile compounds such as n-caproic ac id, isoamyl acetate, n-decyl alcohol, beta-ionone, linalool, and ethyl capo rate. The sensitivity of the sensor ranges from 10(-6)similar to 10(-7) g, fully correlated with the olfactory threshold values of human noses. An arr ay of six sensors consisting of five fractionated ORPs and one referenced p hospholipid probe is able to respond to different odorants and form a typic al fingerprint for each odorant. (C) 1999 Elsevier Science S.A. All rights reserved.