A Bi₁₃S₁₈I₂-based wearable photoelectrochemical biosensor for accurate monitoring of <scp>l</scp>-tyrosine in sweat as a diabetes biomarker

The development of real-time, non-invasive, flexible wearable systems for biomarker monitoring is critical for advancing healthcare diagnostics. Herein, we present a flexible patch consisting of an ultrasensitive photoelectrochemical (PEC) biosensor integrated with a hydrophilic nonwoven fabric sweat-collecting pad for precise, unbiased, and high-performance monitoring of L-tyrosine (L-Tyr) in sweat. The innovative PEC sensor is based on the incorporation of Bi₁₃S₁₈I₂ (BSI) as a photosensitive material, combined with a molecularly imprinted poly(<i>m</i>-phenylenediamine) (MIP) matrix as a biorecognition element. The developed biosensing photoelectrode exhibits an enhanced photoanodic response and improved incident photon-to-current efficiency (IPCE), attributed to optimized energy band alignment, increased visible-light absorption, efficient photo-induced charge separation, and transfer, extended electron-hole pair lifetime, and enhanced electron density and mobility. The platform offers an impressive linear detection range of 80 nM to 350 μM, with a detection limit as low as 24 nM, ensuring accurate and reliable L-Tyr monitoring, which is essential for diabetes care. The sensor exhibited high repeatability, long-term stability, and low cross-reactivity with potential interfering substances, further demonstrating its practicality for use in complex biological environments. This work marks a significant advancement in wearable diagnostic technology, providing a versatile platform for non-invasive biomarker monitoring. The ability to accurately detect L-Tyr in sweat makes this sensor a valuable tool for real-time health monitoring and diagnostics, opening new avenues for future innovations in PEC sensing and biosensing technologies.