Human olfactory system and olfactory biosensor

Although research on olfaction initially began about a hundred years ago and electrophysiological experimental techniques have been used in olfaction research since 1950's, olfaction has not received as much attention as the other senses. However, since Dr. Buck and Dr. Axel received the Novel prize for identifying the olfactory mechanism in 2004, various studies have examined olfactory sensors due to its potential commercial applications. In the olfactory system, the first event for smell sensing is the binding of the odorant molecules to olfactory receptors, which initiates electrical signals. These electrical signals then travel along the axons to the olfactory bulb at the front of the brain. The olfactory receptor can be effectively used as a biological element in olfactory biosensors. Olfactory biosensors can be classified into cell-based and protein-based biosensors. The cell-based biosensor uses living cells that express olfactory receptors as the biological sensing elements and the protein-based biosensor uses the olfactory receptor protein as the biological sensing elements. The signals derived from the binding of odorant molecules to the olfactory receptors can be measured using various devices such as QCM, SPR, microelectrodes, and carbon nanotubes. As a result of the development of various assay systems, the number of deorphanized olfactory receptors is increasing. The ability to use olfactory biosensors in a wide range of different scientific and medical fields for sensing odors is dependent on the development of highly sensitive and selective biosensors. This chapter describes the human olfactory system and olfactory biosensors.