The mechanism by which biological chemosensory systems detect, recognize, and discriminate complex mixtures of chemicals has stimulated interest for the development of electronic analogues of olfaction. The principle of combinatorial selectivity has been the main paradigm for the development of electronic noses. This concept is taken from the biological system where generally individual olfactory receptors are not highly selective for a given odorant. Thus, odorants and responses across large numbers of receptors are encoded in combinatorial patterns whose interpretation leads to the odorant identification. Conventional approaches to machine olfaction are limited due to the types of gas sensors currently commercially available. Most of these are hampered by their lack of selectivity, sensitivity to environmental disturbances, drift, and noise. Achievement of robust sensing and reliable systems even with sophisticated signal and data processing approaches has been limited despite decades of development of electronic nose technology. A paradigm shift is now occurring to overcome these problems. A biomimetic approach to so called “electronic noses” has been adopted where increased understanding of biological chemical sensing can provide new insights into the design of artificial sensing systems. Olfactory receptor proteins and soluble Odorant-binding proteins (OBPs) can now be cloned, modified, and immobilized onto a variety of transducers and several researchers worldwide are now demonstrating the benefits of using these biorecognition elements. We focus on OBPs that are a family of proteins found in chemosensory organs of vertebrates and insects and are associated with detection and release of chemical stimuli. We show that an array of biosensors could be easily constructed based on immobilization of OBPs on to suitable transducers 1,2. Using quartz crystal microbalance platforms, surface acoustic wave devices, or electrochemically gated field effect transistors as a transduction element, it is possible to detect and measure quantitatively concentrations of volatile analytes at parts per million concentrations in air 3,4 and nanomolar concentrations in aqueous solution5. Examples will be given of practical applications of such devices in the field for environmental, security and medical applications.
Keywords: Odour Sensing, Biomimetic Devices, Odorant Binding Proteins, Electronic Noses
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