Flexible and self-healing electrochemical hydrogel sensor with high efficiency toward glucose monitoring

The commercial sensor of a continuous glucose monitoring system suffers from restricted penetration of glucose in the dense sensing coating, uncontrolled leakage of the glucose oxidase and electrocatalytic medium, and susceptibility to mechanical damage. Herein, a self-healing hydrogel based on quaternized chitosan and oxidized dextran was designed, and CeO₂/MnO₂ hollow nanospheres were covalently linked in the hydrogel as the electrocatalytic medium. Glucose oxidase was loaded via the strong electrostatic interactions with the CeO₂/MnO₂ hollow nanospheres. An extra covering agent was coated on the hydrogel to prevent the leakage of the glucose oxidase and electrocatalytic medium. Covalent linkage of the hydrogel on a bendable chip formed a flexible glucose sensor, which showed a wide linear range (1-111 mM), fast response (less than 3 s), and high sensitivity (176 μA mM^-1 cm^-2). The hydrogel-based sensor was self-healable, and could continuously work for over 30 days. Thus, this study provides a method to simultaneously prevent the leakage of the electrocatalytic medium, promote the sensitivity of glucose detection, and tolerate the mechanical damage, which shows great potential for continuous glucose monitoring.