Abstract
Background/Objectives: Magnetically responsive biomaterials have emerged as promising platforms for tissue engineering as they allow remote stimulation of cells and improved control over tissue regeneration. Although gelatin–alginate hydrogels incorporating iron oxide nanoparticles have been reported, the use of U-type hexaferrite particles, particularly Al3+-substituted compositions, remains largely unexplored. This study aimed to develop and characterize extrusion-based 3D-printed gelatin–alginate scaffolds containing U-type hexaferrite particles and to evaluate the influence of particle composition and loading on the rheological, physicochemical and magnetic properties of the resulting biomaterials, as well as their in vitro compatibility with macrophages. Methods: Gelatin–alginate inks containing two U-type hexaferrite compositions (Ba4Co2Fe36−xAlxO60; x = 0.0 and x = 1.0) at two particle loadings (20 and 200 mg) were prepared and processed by extrusion-based 3D printing. The scaffolds were characterized by rheological analysis, SEM-EDS, FTIR, swelling measurements, magnetic responsiveness, and in vitro biological evaluation using RAW264.7 macrophages. Results: The inks exhibited suitable shear-thinning behavior and viscoelastic properties for extrusion-based printing. Increasing particle loading enhanced the thermal resistance of the network, whereas Al3+ substitution modified the viscoelastic response of the polymeric network. The 3D scaffolds successfully responded to an external magnetic field and SEM-EDS confirmed the homogeneous incorporation of hexaferrite particles. The magnetic scaffolds did not compromise macrophage metabolic activity. Conclusions: U-type hexaferrite particles provide an effective strategy for producing 3D-printed magnetically responsive scaffolds with tunable rheological properties without inducing an inflammatory response. The combined modulation of particle composition and loading represents a versatile approach for designing multifunctional inks with potential applications in tissue engineering.