Volumetric Bioprinting of Organoids and Optically Tuned Hydrogels to Build Liver‐Like Metabolic Biofactories

Abstract

Organ‐ and tissue‐level biological functions are intimately linked to microscale cell–cell interactions and to the overarching tissue architecture. Together, biofabrication and organoid technologies offer the unique potential to engineer multi‐scale living constructs, with cellular microenvironments formed by stem cell self‐assembled structures embedded in customizable bioprinted geometries. This study introduces the volumetric bioprinting of complex organoid‐laden constructs, which capture key functions of the human liver. Volumetric bioprinting via optical tomography shapes organoid‐laden gelatin hydrogels into complex centimeter‐scale 3D structures in under 20 s. Optically tuned bioresins enable refractive index matching of specific intracellular structures, countering the disruptive impact of cell‐mediated light scattering on printing resolution. This layerless, nozzle‐free technique poses no harmful mechanical stresses on organoids, resulting in superior viability and morphology preservation post‐printing. Bioprinted organoids undergo hepatocytic differentiation showing albumin synthesis, liver‐specific enzyme activity, and remarkably acquired native‐like polarization. Organoids embedded within low stiffness gelatins (<2 kPa) are bioprinted into mathematically defined lattices with varying degrees of pore network tortuosity, and cultured under perfusion. These structures act as metabolic biofactories in which liver‐specific ammonia detoxification can be enhanced by the architectural profile of the constructs. This technology opens up new possibilities for regenerative medicine and personalized drug testing.

Controlling Light in Scattering Materials for Volumetric Additive Manufacturing

“…Cell‐laden hydrogels may be highly scattering (Figure 4b ). [ 16 ] For volumetric light‐based biofabrication methods, this constrains cell concentration. The proposed scattering correction spatially redistributes light as it is sent in the tomographic patterns.…”

“…Tuning the optical properties of hydrogels with contrast agents to reduce the refractive index mismatch between cells and their medium can improve print fidelity, but it comes at the cost of changing the hydrogel composition. [ 15 , 16 ]…”

Tomographic Volumetric Bioprinting of Heterocellular Bone-like Tissues in Seconds

“…Nevertheless, the limited level of marix mineralization in combination with the absence of mature osteocytic gene signatures (SOST) emphasize the need to further improve our strategies for in vitro osteocytic differentiation. Implementation of the optical tuning method with Iodixanol [27] may enable VBP of bone-like constructs at higher cell densities to accelerate tissue maturation. Other studies have identified additional parameters that can further drive osteogenesis, such as co-culture with macrophage/osteoclast [44] and mechanical stimulation [45] which is a crucial cue for matrix mineralization.…”

“…In this work, we report a new method to fabricate heterocellular bone-like tissues in seconds by leveraging the advantages of ultrafast tomographic VBP technique and 3D hMSC/HUVEC co-culture ( Figure 1 ). Until now, only a handful of publications [8, 26, 27] reported VBP of cell-laden hydrogel constructs. These prior arts highlight that a VBP process is much faster than traditional layer-by-layer printing techniques such as extrusion bioprinting [16, 28].…”

Advances in 3D Gel Printing for Enzyme Immobilization

“…This method enables hydrogel printing at fast rates with high precision and overcomes the technical difficulties of printing unsupported structures, such as overhangs. Applications in printing biomimetic organoids have shown success [ 93 ] and adaptation to enzyme immobilization is likely to happen soon. Meanwhile, rapid biotechnology developments are making it easier to modify native enzymes to include beneficial binding domains [ 31 ] that interact or bond to the 3D printed surfaces spontaneously [ 94 ].…”