Levitational 3D Bioassembly and Density‐Based Spatial Coding of Levitoids

Abstract Self‐assembly of cells into functional bioarchitectures with microscale spatial topographies are prevalent in nature. Despite the advances to recapitulate the native‐like microenvironment in vitro,fabrication of soft living materials with a deterministic control on the composition, functionality, and geometry, is still challenging. Here, a versatile, paramagnetically tunable, levitational biofabrication technique within a ring‐magnet system, RM‐LEV, is developed to assemble single cells or heterogeneous multicellular living architectures in a scaffold‐free manner. The self‐assembly and contactless biofabrication of multiple cell types into 3D multicellular “levitospheres” is demonstrated, where cellular positions are guided by levitation and density, simultaneously. Inherent density and diamagnetism of different cell types are leveraged to manipulate the geometry and self‐assembly of levitospheres into larger complex 3D structures, termed as “levitoids”. This approach is further applied to manipulate, position, and culture levitoids within a 3D hydrogel matrix under levitation, which preserves their viability and functionality. Thus, this study provides a foundation to create spatially heterogeneous 3D cellular assemblies with density‐coded bio‐architectures—which is not previously realized using magnetic levitation. This density‐based coding approach can be beneficial to study the cross‐talk between different cell types within spheroids and organoids, and be broadly applied to 3D bioprinting, tissue engineering, cancer, and neuroscience research.