Integration of Cholesterol Oxidase‐Based Biosensors on a Smart Contact Lens for Wireless Cholesterol Monitoring from Tears

Cholesterol plays a critical role in physiological functions, but elevated levels increase the risk of cardiovascular disease. Regular cholesterol monitoring is essential for elderly or obese individuals. Current methods, such as blood tests, are invasive, inconvenient, and require a professional operator. In contrast, tears, as an accessible body fluid, offer a promising alternative for noninvasive monitoring due to their correlation with blood cholesterol levels. Herein, a noninvasive approach for monitoring cholesterol levels in tears using a biosensor integrated into a smart contact lens is reported. The biosensor employs cholesterol oxidases as the biocatalyst, coupled with an osmium‐based mediator, to detect cholesterol concentrations ranging from 0.1 mM to 1.2 mM in artificial tears. A key challenge is the extremely low cholesterol concentration in tears, which is addressed using a parity‐time (P‐T) symmetry‐based magnetic resonance coupling system. This system enables wireless signal reading and achieves high sensitivity due to its high‐quality (Q) factor, which can achieve a detection limit of 0.061 mM. This portable, high‐sensitivity smart contact lens demonstrates significant potential as a wearable device for continuous, noninvasive cholesterol monitoring. The findings contribute to advancing tear‐based diagnostic systems and highlight the scientific importance of utilizing tear biomarkers for health monitoring.