Robust pH Sensing Using a Graphene Oxide and Covalent Organic Frameworks Composite for Gastro-esophageal Reflux Disease Diagnosis.

Gastro-esophageal reflux disease affects 15-20% of the global population and is commonly diagnosed via 24-h ambulatory pH monitoring. However, current diagnostic tools, including catheter-based systems and ingestible capsules, suffer from poor patient compliance and unreliable pH readings due to sensor degradation in acidic environments. To address this challenge, a robust, composite pH sensor is reported in this work by combining graphene oxide (GO) with covalent organic frameworks (COFs) coatings. Through interfacial polymerization and liquid-phase exfoliation, the COF protective layer is covalently formed on GO sheets, preserving GO integrity in acidic conditions while enhancing electrochemical performance benefitting from the intrinsic porosity of COFs. The COFs nanochannels with sulfonic groups enable selective proton transport, resulting in high ion selectivity and sensitivity (≈43 mV pH-1, in pH 1-10). The sensor exhibits excellent linearity, stability, and high reproducibility in simulated gastric fluid. Furthermore, it resists biofouling from mucin-rich environments and maintains performance under cyclic mechanical deformation. The GO/COFs composites also show biocompatibility with esophageal epithelial cells. These findings suggest that leveraging COFs as biocompatible protective coatings offers a promising strategy for enhancing the robustness and sensitivity of sensing materials in harsh environments and facilitates the future development of ingestible devices for continuous pH monitoring.