Olfactory receptor-based biosensors as potential future tools in medical diagnosis

The detection of biomarkers is the future of non-invasive medical diagnosis and screening. Discovery and identification of reliable disease specific volatile organic compounds is dependent on repeatable, accurate analysis of trace level gaseous analytes mainly in breath samples. Natural variety of the olfactory systems and the compounds capable of gas molecules binding creates wide possibilities of acquisition and implementation of the biological elements for construction of the biosensors for different applications, with special emphasis on healthcare and medical areas. Early and fast diagnosis of patient's condition, including respiratory system diseases, as well as on-time launch of suitable treatment are the critical factors influencing on public health and efficiency of clinical trials. Conventional techniques of diagnosis of the respiratory system diseases are usually time-consuming, require centralized laboratories, experienced personnel and expensive equipment. Recently developed biosensors take advantage of micro- and nanotechnology achievements, which significantly improve their metrological parameters. A transfer of the biosensors from scientific laboratories to actual clinic diagnostics is limited and requires overcoming of critical obstacles. Potential use of olfactory receptors and elements mimicking their operation in artificial olfaction for their use in biosensors in disease diagnosis are presented. We review recent progress in olfactory-based biosensors employing different biological units in light of future developments in medical diagnosis with emphasis on examples where biological components have been employed to detect biomarkers. Also, significant advances over the last years were discussed and features of fabrication in the perspective of odorant sensing applications. Pioneering studies that greatly impacted the field of biosensing are critically reviewed along with future challenges to overcome.