Mechanical stimulation of cells embedded in scaffolds is known to increase the cellular performance toward osteogenic or chondrogenic differentiation and tissue development. Three-dimensional bioplotting of magnetically deformable scaffolds enables the spatially defined distribution of magnetically inducible scaffold regions. In this study, a magnetic bioink based on alginate (alg, 3%) and methylcellulose (MC, 9%) with incorporated magnetite microparticles (25% w/w) was developed and characterized. The size and shape of particles were monitored via scanning electron microscopy and X-ray micro-computed tomography. Shear-thinning properties of the algMC ink were maintained after the addition of different concentrations of magnetite microparticles to the ink. Its viscosity proportionally increased with the added amount of magnetite, and so did the level of saturation magnetization as determined via vibrating sample magnetometry. The printability and shape fidelity of various shapes were evaluated, so that the final composition of algMC + 25% w/w magnetite was chosen. With application of this ink, cytocompatibility was proven in indirect cell culture and bioplotting experiments using a human mesenchymal stem cell line. Toward the deformation of cell-laden scaffolds to support cell differentiation in the future, radiography allowed the real-time monitoring of magnetically induced deformation of scaffolds of different pore architectures and scaffold orientations inside the magnetic field. Varying the strand distance and scaffold design will allow fine-tuning the degree of deformation in stimulatory experiments.
Keywords: 3D bioprinting; alginate; biomaterials; magnetic hydrogels; magnetically actuated deformation; magnetite; tissue engineering.