Granular hydrogel bioink for macroporous pancreatic spheroid scaffolds.

Cells positioned more than several hundred microns away from a vascular network experience insufficient oxygen and nutrient supply due to diffusion limitations, leading to compromised viability and impaired function. This challenge is especially relevant in large, engineered 3D constructs which exceed the diffusion limitation of 100 - 200 µm, resulting in necrotic cores. Granular hydrogels have emerged as a promising approach for tissue engineering due to their inherent porosity. Their interconnected pores can facilitate mass transport of oxygen and nutrients, and therefore support cellular function. In this work, we developed a facile method to prepare bioprintable granular hydrogel bioink containing microparticles with tunable diameters, that can form porous scaffolds with different pore sizes and porosities. The bioink remained shelf-stable for at least 60 days when stored at 4 °C, as determined by the melt temperature. The macroporous granular hydrogel scaffold has inherent void spaces between the hydrogel microparticles, in which spheroids can be embedded. Pancreatic spheroids incorporated into the scaffold showed improved viability compared to free spheroids, indicating the granular microenvironment supports spheroid survival. Furthermore, functional studies of embedded pancreatic spheroids with glucose-stimulated insulin secretion (GSIS) demonstrated preserved insulin secretion functionality. Our approach thus serves as a tunable platform for supporting the culture of functional spheroids and organoids, that has potential regenerative medicine applications in restoration of physiological functions when implanted.