High-frequency magnetic fields for fine tuning particle scaffolds in living self-healing hydrogels.

Living tissues exhibit a complex, anisotropic, and hierarchical organization. Replicating cellular alignment within a biomimetic extracellular matrix remains a significant challenge, particularly in hydrogels, whose randomly crosslinked polymer networks inherently form isotropic structures. Here, we present an approach for engineering in vitro cytocompatible structured hydrogels using magnetic particles under previously unexplored high-frequency magnetic fields. By applying programmable high-frequency biaxial and triaxial magnetic fields, we control particle self-assembly during gelation and generate distinct volumetric architectures within an oxidized-laminarin/gelatin hydrogel precursor. Upon gelation, the external field can be removed, leaving a stabilized three-dimensional particle structure. This structure, in turn, provides persistent physical cues for fibroblast alignment, elongation, and migration under in vitro culture conditions. The ability to structure hydrogels in their liquid phase establishes a programmable platform for engineering anisotropic living hydrogel scaffolds, while future in vivo studies will be required to assess tissue integration, inflammatory response, particle retention, and translational potential.