Designing Porosity-TailoredHydrogel Sponges withControlled Cell Positioning Using Dispersible, Autofragmented SacrificialMicrofibers

Hydrogel encapsulation is a rational approach that facilitates three-dimensional inoculation, arrangement, and culture of living mammalian cells for biomedical applications. However, strategies to form capillary-like conduits in hydrogels remain challenging due to low spatial resolution and difficulty in controlling the location of multiple cell types. Herein, we propose a highly unique process of constructing hydrogel sponges with tailored pore densities using finely fragmented microfibers as sacrificial porogens. A facile production process for automatically fragmented hydrogel microfibers (AF fibers) was developed through micronozzle-assisted hydrodynamic spinning and shear force application during gelation. Hydrogel sponges were prepared using photo-cross-linkable gelatin as the matrix and AF fibers dispersed in the precursor solution. We cultured liver cells in the sponges and evaluated the morphology and pore connectivity of the sponges and cellular functions. Furthermore, to create tissue models highly mimicking the cellular assembly <i>in vivo</i>, coculture of two types of cells was demonstrated in a position-controlled manner using cell-encapsulating AF fibers. The proposed approach of rationally designing hydrogel sponges is highly versatile in 3D cell culture for cell-based drug evaluation and regenerative medicine because of the simplicity of preparation and its impact on cellular functions.