Reusable electrochemical impedance spectroscopy biosensor for the detection of cortisol in sweat: Introducing novel techniques suitable for future affective wearable devices and emotional stress.

Abstract

Skin conductivity is used in emotion and stress-detecting systems based on physiology (sweat). However, these technologies do not detect sweat biomarkers or utilize sweat's biological information. Stress-induced volatile organic compounds (VOCs) cannot be detected using these methods. This study explores biomarkers of human emotional stress and identifies key indicators for wearable sensors in affective systems. Crime, health, the economy, and quality of life are all affected by emotional stress. Blood cortisol testing, electroencephalography, and physiological parameter techniques are the gold standards for stress measurement; nevertheless, they are expensive, inconvenient, and impractical for wearable real-time stress monitoring, such as a smartwatch, due to their single-use design. Instead, sweat cortisol was found as the critical stress biomarker for wearable affective system sensors in this study. Modern sensor research aims to create synthetic receptors with similar selectivity and sensitivity to natural antibody-antigen behaviour. This molecular recognition could lead to selective, sensitive sensors that can identify and monitor targets noninvasively when paired with modern methods for monitoring recognition element modifications. Molecularly imprinted polymers, MIPs, are synthetic antibody-antigen systems. They selectively bind their production molecule using a "lock and key" method. MIPs may offer biological receptor specificity and selectivity with environmental durability and low cost. The current study explores the feasibility of using MIPs technology to detect cortisol in sweat for real-time monitoring of emotional stress episodes. A conceptual approach is given to make MIPs sensors more usable for monitoring cortisol sweat in wearable devices. As seen in the reviewed literature, cortisol and MIPs are under-researched biomarkers and their biosensors from the reviewed literature. Experiments employing electrochemical impedance spectroscopy techniques on a capacitance MIP confirmed this theory. It successfully detects cortisol within the physiological range as the higher response is recorded for a greater concentration. The literature also shows that no MIP biosensor is reusable in portable electronics. This work used a function generator simulation to evaluate the hypothesis that the target extraction technique employed Abstract Abdulaziz Zamkah 2023 Page iii during the MIPS fabrication step is repeatable and suitable for employment in wearables.