Glucose-sensitive and 3D-printable dynamic chitosan hydrogels from boronic acid-functionalized chitosan and...

Chitosan-based hydrogels are attractive candidates for biofabrication due to their biocompatibility and bioactivity; however, their application in 3D printing is limited by poor mechanical stability, often resulting in structural collapse during printing. Here, a self-healing chitosan gallol-chitosan boronic acid (CGB) hydrogel ink is developed through the dynamic coordination of a gallol-functionalized (CG) chitosan and a boronic acid-functionalized (CB) chitosan, enabling robust 3D printability at a low overall solid content of 2 wt%. Rheological and small-angle X-ray scattering analyses unveiled that CG or CB alone can self-assemble in solution, forming rod-shaped clusters. The dynamic boronate ester crosslinking between the two functionalized chitosans induces a highly compact, fractal-like network with enhanced short-range organization, effectively reinforcing the resulted hydrogel (CGB). This structural organization imparts pronounced shear-thinning behavior, allowing extrusion through a 160 μm nozzle and fabrication of highly stacked constructs up to 60 layers while maintaining shape fidelity. The high stackability and versatile responsiveness enable its application as a customizable visual redox sensor and glucose-sensitive sacrificial material for fabricating hierarchically layered microchannels with 90°-rotated H-shaped architectures. The CGB hydrogel also exhibits potent antimicrobial activity and achieves >90% viability for embedded cells, representing a promising chitosan hydrogel ink for fabricating complex, bioactive 3D constructs.