This work reports the rational design and fabrication of magneto-active
microfiber meshes with controlled hexagonal microstructures via melt
electrowriting (MEW) of a magnetized polycaprolactone-based composite. In
situ iron oxide nanoparticle deposition on oxidized graphene yields
homogeneously dispersed magnetic particles with sizes above 0.5 μm and
low aspect ratio, preventing cellular internalization and toxicity. With these
fillers, homogeneous magnetic composites with high magnetic content (up to
20 weight %) are obtained and processed in a solvent-free manner for the first
time. MEW of magnetic composites enabled the creation of skeletal
muscle-inspired design of hexagonal scaffolds with tunable fiber diameter,
reconfigurable modularity, and zonal distribution of magneto-active and
nonactive material, with elastic tensile deformability. External magnetic fields
below 300 mT are sufficient to trigger out-of-plane reversible deformation. In
vitro culture of C2C12 myoblasts on three-dimensional (3D)
Matrigel/collagen/MEW scaffolds showed that microfibers guided the
formation of 3D myotube architectures, and the presence of magnetic
particles does not significantly affect viability or differentiation rates after 8
days. Centimeter-sized skeletal muscle constructs allowed for reversible,
continued, and dynamic magneto-mechanical stimulation. Overall, these
innovative microfiber scaffolds provide magnetically deformable platforms
suitable for dynamic culture of skeletal muscle, offering potential for in vitro
disease modeling.

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