Thermally Degradable Biocompatible Hydrogel as Transient Encapsulation Coating for Implantable Sensors

Implantable sensors are redefining real-time, continuous physiological monitoring and hold great promise for personalized medicine. Yet, their clinical application is often hindered by the lack of effective encapsulation materials that simultaneously ensure environmental exposure and protect sensor components, thereby preserving signal fidelity. Although hydrogel-based systems offer promising features such as biological tissue-like mechanics and biocompatibility, their use as sensor coatings remains limited. Notably, despite growing interest in bioresorbable implant technologies, few coating systems offer controlled, on-demand degradability, which represents a key requirement to avoid possible misalignment between coating dissolution rate and sensor lifetime. Here, we present a thermoresponsive hydrogel, consisting of methylcellulose, polyethylene glycol and polyacrylic acid (MC/PEG/PAA), demonstrating its high suitability as a transient encapsulating coating. The system, assembled by physical cross-linking without using toxic reagents, and extensively characterized in terms of thermal responsiveness, swelling behavior, stability, and mechanical performance, exhibited reversible dissolution upon a mild temperature drop (from ≈37°C to ≈25°C), which was conveniently used to easily enable its degradation under physiological conditions. The hydrogel ability to act as a coating was demonstrated via the encapsulation of a fluorescent model device, confirming its optical transparency and signal-transmission capability. In vitro studies indicated the hydrogel potential to mitigate inflammatory response, while in vivo biocompatibility, assessed in mice, revealed no signs of systemic toxicity or behavioral changes post-implantation. Additionally, the hydrogel exhibited safe in vivo biodegradation upon a slight local temperature decrease, completely dissolving within few minutes. The developed coating, integrating good optical transparency, ease of fabrication, and in vivo safety with on-demand, controllable degradation upon an external low-temperature stimulus, represents a substantial advancement toward next-generation bioresorbable implantable devices and paves the way for driving successful transformation in the field.