Biocompatible Ink Optimization Enables Functional Volumetric Bioprinting With Xolography

Xolography is a novel linear volumetric manufacturing technique that offers unparalleled precision and speed. Yet, its application to bioprinting remains limited due to insufficient understanding of biocompatibility constraints. Here, this work establishes fundamental design principles for cell-compatible Xolography bioinks by dissecting the effects of extracellular pH, osmolality, and lysosomotropic stress on cell viability and function. By systematically studying the tolerances for these parameters, this work defines a framework for bioink formulations that enables fast, support-free fabrication of complex designs with maintained cell viability and function as validated in different murine and human cell lines, primary human cells and induced pluripotent stem cell (iPSC)-derived cells. These results show that, unlike triethanolamine, BisTris indeed can function as a fully biocompatible co-initiator enabling cell viability beyond 90% as well as uncompromised metabolic activity and differentiation performance when used in a tightly controlled formulation, contrasting previous reports. This work showcases the biomedical potential of the formulation by achieving fibroblast-driven extracellular matrix (ECM) formation, endothelial sprouting from pre-vascularized spheroids, and maintenance of an iPSC-derived hepatocyte differentiation phenotype within Xolography-printed constructs. These advancements transform Xolography into a powerful and foremost reliable bioprinting platform for fabrication of complex, cell-laden structures for versatile applications in tissue engineering, organ-on-a-chip models, and regenerative medicine.