Demonstration of sweat-based circadian diagnostic capability of SLOCK using electrochemical detection modalities

Abstract

SLOCK is a sweat-based circadian diagnostic platform used for mapping the user's chronobiology via cortisol and DHEA. In this work, we have demonstrated the detection capabilities of this sweat-based sensing platform using two electrochemical sensing modalities: Electrochemical Impedance Spectroscopy (EIS) and chronoamperometry. Wicking simulations for vertical versus horizontal flow patterns under potential bias were evaluated using COMSOL Multiphysics®. This work also highlights the biorecognition element characterization using Surface Plasmon Resonance (SPR) and FTIR. Sensor platform was evaluated for biomarker concentrations using doses spanning physiological ranges of 8–141 ng ml⁻¹ and 2–131 ng ml⁻¹ for cortisol and DHEA, respectively. Detailed analysis of impedance data is supported with electrochemical fitting of circuit components related to the biosensing process. Finally, human subject-based studies have been performed to understand the effect of sweating rate with respect to gland density on biosensing. Also, on-body mechanical resiliency studies have been performed to highlight the flexibility of this serpentine electrode-based sensing platform. The platform responds sensitively to the amount of circadian relevant biomarkers in the system with a limit of detection of 0.1 ng ml⁻¹ for both cortisol and DHEA. Thus, the SLOCK platform offers to be an attractive vessel for facilitating the electrochemical detection of circadian relevant biomarkers and for self-monitoring of user's chronobiology.