Electroanalytical Measurement of Steroid Hormone with Carbon Electrode Sensor

Cortisol is a vital steroid hormone that has been known as the “stress hormone,” which is elevated during times of high stress and anxiety. The improved detection of cortisol is critically important as it will help further our understanding of stress during several physiological states. Several methods exist to detect cortisol, however, they suffer from low biocompatibility, spatiotemporal resolution, and are relatively slow. In this study, we developed an assay to measure cortisol with carbon fiber microelectrodes (CFMEs) and fast-scan cyclic voltammetry (FSCV). FSCV is typically utilized to measure small molecule neurotransmitters by producing a readout CV for the specific detection of biomolecules on a fast, subsecond timescale with biocompatible CFMEs. It has seen enhanced utility in measuring peptides and other larger and more complex molecules. We developed a waveform to electro-reduce cortisol at the surface of CFMEs. The sensitivity of cortisol was found to be 5 nA/uM and was adsorption controlled on the surface of CFMEs and stable over several hours. Cortisol was co-detected with several other biomolecules such as dopamine and serotonin, and the waveform was fouling resistant to repeated injections of cortisol on the surface of the CFMEs. Furthermore, we also measured exogenously applied cortisol onto brain tissue and simulated urine to demonstrate biocompatibility and potential use in vivo . The specific biocompatible detection of cortisol with high spatiotemporal resolution will help further elucidate its biological significance and further understand its physiological importance in the brain.