The coprecipitation-functionalized 3D-printed GM/PDA/PRF hydrogel for infected bone regeneration via synergistic photothermal antibacterial and osteogenic activity.

To address insufficient osteogenesis and persistent infection in infected bone defects, we developed a dual-functionalized hydrogel by integrating polydopamine (PDA) and platelet-rich fibrin (PRF) into a 3D-printed gelatin methacryloyl/methylcellulose (GM) matrix. Two functionalization strategies, surface adsorption and coprecipitation, were employed to fabricate GM/PRF-A and GM/PRF-C scaffolds. Comprehensive characterization revealed both scaffolds exhibited favorable hydrophilicity, controllable degradation and improved mechanical properties. The incorporation of PDA within hydrogels displayed NIR-responsive photothermal antibacterial activity, as well as serving as a bio-adhesive to stabilize PRF and enable on-demand growth-factor release. Both functionalization strategies promoted the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Compared with the adsorption-based scaffold, the coprecipitation-functionalized hydrogel showed more sustained growth-factor release, better antibacterial efficacy, and superior osteogenic performance in vitro and in an infected calvarial defect model. These findings indicated that coprecipitation-functionalized GM/PDA/PRF hydrogel was a promising strategy for infected bone regeneration.