Co‐Encapsulating Enzymes and Carbon Dots in Metal–Organic Frameworks for Highly Stable and Sensitive Touch‐Based Sweat Sensors

Abstract

Wearable metabolite sensors are often limited by easily denaturable enzymes that only allow short‐duration monitoring. Although encapsulating enzymes in metal–organic frameworks (MOFs) shows promise of long‐term enzyme protection, it is typically accompanied by significantly decreased activity due to increased diffusion barrier, steric hindrance for enzyme‐substrate binding, and poor enzyme‐electronic interface. Herein, the co‐encapsulation of enzymes and ultrasmall arginine‐derived carbon dots (Argdot) into a mesoporous Zeolitic Imidazolate Framework‐8 (mZIF‐8) matrix and the enhancement effect of Argdot on enzyme stability and activity, which consequently improves the electrochemical sensor's long‐term sensitivity are investigated. Specifically, the glucose oxidase (GOx)‐Argdot@mZIF‐8 nanocomposite consistently exhibits 40% higher electrochemical sensitivity compared to control GOx@mZIF‐8, an improvement similarly demonstrated with another model enzyme lactate oxidase (LOx). Furthermore, GOx‐Argdot@mZIF‐8 displays excellent stability, retaining 100% of initial sensitivity over 30 days of repeated testing at 37 °C. A touch‐based glucose sensor prototype is demonstrated as an excellent reusable sensor to monitor finger‐tip sweat glucose levels over one month at room temperature. This enzyme encapsulation strategy is not only useful for developing reusable sweat sensors with long‐term monitoring capability, but also promising to expand the industry use of enzymes under harsh conditions.