(443e) Cellular Snowballing: Assembling Bio-Based Microgels and Cells to Build Tissues

Generating three-dimensional (3D) tissue models in vitro is essential for mirroring the intricate structures and functionalities of human tissues. Nevertheless, conventional techniques often yield dense cellular formations with compromised cell viability, primarily due to insufficient oxygen and metabolite exchange. To overcome these challenges, we introduce an innovative method for crafting sizable biohybrid spheroids (BHS). This method leverages adherent cells as building blocks and utilizes cell-adhesive biopolymer-based hydrogel microparticles (microgels) as substitutes for the extracellular matrix (ECM). Through 2D co-culture, cells and hydrogel particles synergistically initiate the self-assembly of 3D BHS, reminiscent of a snowballing effect driven by cell adhesion and migration. The aggregation kinetics and final size of BHS are modifiable by adjusting microgel size and the ratio of cells to microgels. Notably, using microgels considerably larger than the cells results in porous BHS, enhancing diffusion and ensuring cell viability even in millimeter-scale aggregates. An agent-based model accurately reproduces the cellular snowballing assembly process, offering insights into assembly kinetics and determining the ultimate size of the spheroids. Our BHS technique holds promise as a predictive and scalable approach for constructing large tissue models in vitro, potentially revolutionizing biofabrication and facilitating the development of physiologically relevant, large-scale tissue models.