Bioinspired cellulose nanofibril/xylan/gelatin nanocomposite hydrogels with tunable structure for extrusion-based 3D printing and controlled release

Bio-based nanocomposite hydrogels with controllable network structures are attractive candidates for functional printable materials. In this work, a bioinspired cellulose nanofibril (CNF) /xylan/gelatin hydrogel system was developed through the integration of CNF, aldehyde-functionalized xylan (Xyl-CHO), and allylated gelatin (GelA). The hydrogel network was constructed via dynamic Schiff base bonding between Xyl-CHO and gelatin amines together with photo-triggered thiol–ene click crosslinking of GelA, while CNFs served as a reinforcing nanofibrillar scaffold. The synergistic interactions between covalent crosslinks, dynamic bonds, and nanofiber entanglement enabled effective regulation of the hydrogel microstructure and mechanical properties. By tuning the Xyl-CHO content, the pore structure, swelling behavior, and crosslinking density of the hydrogels could be precisely controlled, resulting in a significant improvement in compressive strength and modulus. Rheological measurements revealed pronounced shear-thinning behavior and rapid structural recovery, allowing stable extrusion and high-fidelity fabrication of complex structures via direct ink writing 3D printing. Using levofloxacin as a model compound, the hydrogels exhibited tunable release profiles governed by the interplay between network crosslinking density and matrix swelling. The results demonstrate that the GelA/CNF/Xyl-CHO system provides a versatile platform for designing sustainable, structurally tunable hydrogel materials with excellent printability and controllable release behavior.