Development of a portable cortisol biosensor [abstract]
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Cortisol is a small steroid hormone that is also known as the stress hormone. During times of stress, cortisol levels in mammals have been shown to be elevated. Current methods for measuring cortisol concentration are relatively accurate, but not portable. These methods require samples to be sent to a laboratory for analysis. A portable cortisol biosensor would provide a valuable tool for researchers and clinicians who require quick, onsite sample analysis. The aim of this project is to investigate different immunoassay techniques that could be translated into a portable, fiber optic biosensor. Two immunoassay techniques are being investigated. This first technique was a double antibody sandwich assay. This assay required two cortisol antibodies, one labeled with a fluorescent dye and one without. For this assay to be functional, it was imperative that cortisol binds to both antibodies. Tests were performed and the results indicated that the two antibodies were not a sandwich pair, i.e., they both did not bind to the cortisol. This was due to the minute size of the cortisol molecule which prevented dual binding. Therefore, a second technique is being investigated which involves a competitive binding assay between fluorescently labeled and unlabeled cortisol. A known amount of fluorescently labeled cortisol as well as the unknown amount of unlabeled cortisol (sample) is exposed to the immobilized antibody. The labeled and unlabeled cortisols compete for binding on the antibodies and the resulting fluorescence is correlated to the amount of unlabeled cortisol. This immunoassay is currently in development and results are being acquired.