Composition Tuning of Semi-Open Cell Carriers via Phase Freeze-Shrink Self-Molding.

Extracellular matrix (ECM)-mimicking microsized cell carriers featuring a semi-isolated chamber facilitate the study of cellular heterogeneity as well as intercellular communication. However, the semiopen shaping of the designated gel mixture remains unattainable with current methods. We report an oil-phase freeze-shrink self-molding mechanism for generating size- and composition-tunable cradle-shaped microgels (microcradles) from water-in-oil droplets. The universality of this shape transition principle is demonstrated with six types of polysaccharides dispersed in a poly(ethylene glycol) diacrylate (PEGDA) or methacrylate gelatin (GelMA) matrix. By doping the microcradles with the major ECM component, hyaluronic acid sodium, we demonstrate a label-free selective culture of CD44 receptor-rich cells and the formation of cell spheroids within 3 days. This cryo-induced cradle-shaping strategy enables the functionalization of microcarriers for selective cell culture, thereby allowing them to be used for intercellular communication, drug delivery, and the construction of structural units for osteogenesis and 3D printing.