Expanding Embedded 3D Bioprinting Capability for Engineering Complex Organs with Freeform Vascular Networks.

Creating functional tissues and organs in vitro on demand is a major goal in biofabrication, but the ability to replicate the external geometry of specific organs and their internal structures such as blood vessels simultaneously remains one of the greatest impediments. Here, we address this limitation by developing a generalizable bioprinting strategy of sequential printing in a reversible ink template (SPIRIT). We demonstrated that our microgel-based biphasic (MB) bioink can be used as both an excellent bioink and a suspension medium that supports embedded 3D printing due to its shear-thinning and self-healing behavior. When encapsulating human-induced pluripotent stem cells (hiPSCs), the MB bioink was 3D printed to generate cardiac tissues and organoids by extensive stem cell proliferation and cardiac differentiation. By incorporating MB bioink, the SPIRIT strategy enabled the effective printing of a ventricle model with a perfusable vascular network, which is not possible to fabricate using extant 3D printing strategies. Our SPIRIT technique offers an unparalleled bioprinting capability to replicate the complex organ geometry and internal structure in a faster manner, which would accelerate the biofabrication and therapeutic applications of tissue and organ constructs. This article is protected by copyright. All rights reserved.