Magnetic bioprinting: shaping initial tissue geometry and probing tissue mechanics

Mechanical and geometric cues play a crucial role in vivo, regulating both morphogenetic processes and proper tissue function. This is particularly evident in skeletal muscle, where aligned architecture is essential for myogenesis and functional force generation. However, precisely engineering tissue geometry at both macroscopic and microscopic scales while simultaneously controlling internal mechanical forces remains a significant challenge. In this study, we introduce a magnetic tissue engineering platform based on a magnetic bioprinting technique, enabling control of biophysical cues that guide in vitro tissue organization. Applied here to skeletal muscle, this approach allows for the rapid fabrication of cohesive tissues in any desired shape using cells labeled with magnetic nanoparticles. Additionally, multiple cell types can be incorporated and spatially organized within the same construct through magnetic segregation. As the tissues tend to transition toward a spherical shape after a few days, their geometry was optimized to further enable magnetic actuation, including the ability to trap and maintain tissue shape over time. Furthermore, this magnetic platform facilitates the investigation of how tissue architecture influences mechanical properties, such as resistance to rupture. Overall, this study highlights the significant potential of magnetic bioprinting and stimulation for controlling tissue morphology and advancing biomechanical research.