Biosensing of Steroid Hormones with 3D Zinc Oxide Tetrapods.

Accurate monitoring of stress hormones is essential for understanding physiological responses and optimizing human performance. Selective and precise detection of these biomarkers is particularly important for evaluating stress levels in high-demand environments. Herein, we report a multimodal sensor based on zinc oxide tetrapods (ZnO-Ts) for the detection of cortisol and testosterone. The platform integrates fluorescence and electrochemical transduction, enabling a complementary and highly sensitive analysis. ZnO-Ts exhibited fluorescence quenching upon interaction with steroid hormones with detection limits of 0.16 μg/dL for cortisol and 0.25 μg/dL for testosterone. Stern-Volmer and time-resolved photoluminescence analyses revealed analyte-dependent quenching behavior, with cortisol exhibiting a dynamic quenching component and testosterone showing static quenching. A solid-state electrochemical sensor was further fabricated by embedding ZnO-Ts in a poly-(vinyl alcohol) matrix and depositing them onto printed silver electrodes, which demonstrated concentration-dependent electrochemical responses with higher sensitivity toward cortisol. By a combination of optical and electrochemical readouts, this dual-mode sensing strategy provides robust, rapid, and scalable hormone monitoring. The platform's biocompatibility and duality in identifying two steroidal hormones selectively underscore its potential for wearable diagnostics and point-of-care stress monitoring technologies.