Multi-Scale Light-Based Biofabrication of Acrylate-Free Magnetic Gelatin Composites for Transient Vascular Navigation

Photocurable hydrogels derived from native proteins offer high bio-functionality for biomedical micro-devices; however, traditional approaches require chemical functionalization such as methacrylation, altering native bio-activity. Here, an acrylate-free photocurable magnetic composite ink is developed using native gelatin photocrosslinked via ruthenium-mediated di-tyrosine coupling and loaded with zinc-substituted iron oxide (ZFO) nanoparticles. Incorporating magnetic nanoparticles introduces an inherent trade-off between magnetic responsiveness and light penetration during light-based fabrication. By systematic optical and photorheological mapping, an upper processing window of 6 wt% nanoparticle loading under the standard irradiation conditions is established, preserving hydrogel network density at stiffness of ~2 kPa while maintaining printability. The precursor ink is capable of printing structures across length scales via mold casting, digital light processing (DLP), and two-photon polymerization (TPP). The ZFO nanoparticles show dose-dependent cytocompatibility, with cell viability above the ISO 10993-5 threshold (70%) up to 150 µg mL−1, and the dried ZFO-loaded hydrogels show superparamagnetic-like behavior, reaching about 42% of saturation (8.4 emu g−1) at 25 mT. Electromagnetic navigation demonstrates shape-programmed directional alignment, gradient-driven translation, selective Y-junction branch navigation, and 3D out-of-plane friction reduction. Finally, the composites exhibit passive disintegration under simulated physiological conditions within two weeks, presenting a versatile platform for transient bio-hybrid medical micro-devices.