Rapid Tissue Perfusion Using Sacrificial Percolation of Anisotropic Networks

Microfiber-Templated Porogel Bioinks Enable Tubular Interfaces and Microvascularization Down to the Building Blocks for 3D Bioprinting

Vascularization is key to the biofabrication of large-scale tissues. Despite the progress, there remain some outstanding challenges, such as limited vessel density, difficulty in fabricating microvasculatures, and inhomogeneity of post-seeding cells. Here, a new form of bioink called microfiber-templated porogel (µFTP) bioink is introduced to engineer vasculatures down to the filament building blocks of 3D bioprinted hydrogels. The cell-laden sacrificial microfibers (diameter ranges from 50-150 µm) are embedded in the bioink to template tubular voids and deliver endothelial cells for in-situ endothelialization. The inclusion of softening hydrogel microfibers retains the desirable rheological properties of the bioink for extrusion-based bioprinting and the microfibers are well inter-contacted in the extruded filament. Such bioinks can be printed into a well-defined 3D structure with tunable tubular porosities up to 55%. Compared to the conventional bulk bioink counterpart, the µFTP bioink supports the significant growth and spread of endothelial cells either embedded in the matrix or sacrificial fibers, free of the post-cell seeding procedure. Furthermore, the bioprinted scaffolds based on µFTP bioink are seen to significantly promote the in-growth of blood vessels and native tissues in vivo. The µFTP bioink approach enables the engineering of tubular bio-interfaces within the building blocks and contributes to the in-situ endothelialization of microvasculatures, providing a versatile tool for the construction of customized vascularized tissue models.

Sacrificial Templating for Accelerating Clinical Translation of Engineered Organs

Transplantable engineered organs could one day be used to treat patients suffering from end-stage organ failure. Yet, producing hierarchical vascular networks that sustain the viability and function of cells within human-scale organs remains a major challenge. Sacrificial templating has emerged as a promising biofabrication method that could overcome this challenge. Here, we explore and evaluate various strategies and materials that have been used for sacrificial templating. First, we emphasize fabrication approaches that use highly biocompatible sacrificial reagents and minimize the duration that cells spend in fabrication conditions without oxygen and nutrients. We then discuss strategies to create continuous, hierarchical vascular networks, both using biofabrication alone and using hybrid methods that integrate biologically driven vascular self-assembly into sacrificial templating workflows. Finally, we address the importance of structurally reinforcing engineered vessel walls to achieve stable blood flow in vivo, so that engineered organs remain perfused and functional long after implantation. Together, these sacrificial templating strategies have the potential to overcome many current limitations in biofabrication and accelerate clinical translation of transplantable, fully functional engineered organs to rescue patients from organ failure.

Microfluidic Engineering of Addressable Multicompartmental Microspheres for Multicellular Systems

With the advantages of high-throughput manufacturing and customizability, on-microsphere construction of in vitro multicellular analytical systems has garnered significant attention. However, achieving a precise, biocompatible cell arrangement and spatial signal analysis in hydrogel microspheres remains challenging. In this work, a microfluidic method is reported for the biocompatible generation of addressable supersegmented multicompartmental microspheres. Additionally, these microspheres are developed as novel label-free multicellular systems. In the microfluidic approach, controllable microfluidics is used to finely tune the internal microstructure of the microspheres, and the gas ejector ensures the biocompatibility of the preparation process. As a proof of concept, six- and twenty-compartment microspheres were obtained without the addition of any biohazardous reagents. For microsphere decoding, the visualization of two basic compartments can provide clues for identifying label-free cells due to the structural regularity of the microspheres. Finally, by encapsulating cells of different types, these microspheres as multicellular systems were successfully used for cell coculture and drug testing. These biocompatible, scalable, and analyzable microspheres will open up new prospects for biomedical analysis.