Long-Term Stable Wearable Electrochemical Aptamer Sensor for Cortisol in Artificial Sweat Based on a Gold...

A wearable electrochemical aptamer sensor for cortisol was developed on a screen-printed electrode bearing a gold nanoparticle-carboxymethyl cellulose-methylene blue interface. The redox layer was formed by on-electrode electropolymerization of methylene blue in the presence of gold nanoparticles and carboxymethyl cellulose, which helps stabilize the film and supports Au-S anchoring of the thiolated aptamer. Analytical cortisol measurements were performed in artificial sweat with controlled ionic strength and pH. The sensor provided a limit of detection of 0.09 pg mL^-1 and a linear range of 0.0001-1000 ng mL^-1 (mean ± SD, n ≥ 3). Interference from common sweat constituents was minimal, and batch-to-batch reproducibility was good. The device retained 93.4% of its initial response after 56 days of storage at 4 °C (RSD = 2.4%). These results demonstrate a stable wearable transducer platform for cortisol sensing in artificial sweat, and validation in real human sweat will be pursued in future work.