Fundamental Study of Odorant Responses of Desiccatable Cells

An artificial or electronic nose (e-nose) for odor recognition has been a goal for many decades. However, the primary and best means of odor identification in the field today are still dogs, rats, and humans. Dogs can detect COVID, rats can find landmines, and humans can recognize wine vintages. However, all require extensive individual training and none leave an electronic record. A portable artificial nose would have applications in many fields, from food safety to security. Biohybrid sensors are a promising approach, since they combine the ability of biological cells to detect odors with technology to record the cell responses. However, the application of such sensors has been hindered by the need to keep the cells alive continuously. The purpose of this project is to understand whether a new cell line that can be completely dried, similar to the way yeast is dried, could form the basis for a fieldable artificial nose. Dryable cells derived from an insect have been created that give a fluorescence signal when they detect an odor. The cells can be stored under a wide range of environmental conditions in the dry state before they are needed, and can be revived by the addition of liquid. This project seeks to understand the responses of these cells to various odors and exposure conditions. Artificial odor recognition would have a vast range of applications beneficial to society. While biological odor sensing systems have unrivalled selectivity and sensitivity due to specific recognition and combinatorial coding, the challenge to practical realization of biohybrid sensors has been maintenance and storage of the biological elements in a functional state. This fundamental research is on the responses of a desiccatable insect cell line that has been engineered to express an olfactory receptor (OR) and a fluorescence signal upon odorant binding. These novel cells can be kept in a hibernating state, under a wide range of temperatures, until use, circumventing that obstacle. The research objective is to understand whether and how such cells could be employed in a future artificial nose. The research includes 4 tasks. 1) Obtain the concentration-response curves to a panel of odorants and compare them to the known responses of the corresponding olfactory sensory neurons. 2) Ascertain the sources and magnitudes of response variability and explore the issue of calibration. 3) Determine what information the time courses of the responses may contain. 4) Examine the response of the cells to their cognate ligand (the odorant to which they bind most strongly) in the presence of other odorants. The ability to treat the biological components of the sensor essentially as a material similar to a polymer would be ground-breaking and may one day allow biohybrid sensors to leave the laboratory. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.