Assembly of RGD-Modified Hydrogel Micromodules into Permeable Three-Dimensional Hollow Microtissues Mimicking in Vivo Tissue Structures.

Fabricated microscale tissues that replicate in vivo architectures have shown huge potential in regenerative medicine and drug discovery. Owing to the spatial organization of cell-encapsulated hydrogel microstructures, three-dimensional (3D) tissue structures have been broadly applied as novel pathological or pharmacological models. However, the spatial reorganization of arbitrary microstructures with tissue-specific shapes into 3D in vitro microtissues that mimic the physiological morphology and nutrient diffusion of native tissues presents a major challenge. Here, we develop a versatile method that engineers permeable 3D microtissues into tissue-specific microscopic architectures. The customized, arbitrarily shaped hollow micromodules are prepared by photocopolymerizing poly(ethylene glycol) diacrylate (PEGDA) with acryloyl-PEG-Arg-Gly-Asp-Ser (RGDS). These micromodules are spatially reorganized and self-aligned by a facile assembly process based on hydrodynamic interactions, forming an integrated geometry with tissue-specific morphology and a vessel-mimetic lumen. The RGD linkages create cell-adhesive structures in the PEGDA hydrogel, greatly increasing the long-term cell viability in 3D microtissue cultures. Meanwhile, the mechanical properties for fast cell spreading inside the microstructures can be optimized by modulating the PEGDA concentration. The 3D microtissues, with their different geometries and permeable tubular lumens, maintained cell proliferation over 14 days. The cell viabilities exceeded 98%. We anticipate that our method will regenerate complex tissues with physiological importance in future tissue engineering.