A team led by researchers at the University of Illinois Chicago and UC Davis has developed a method to 3D bioprint tissue-specific, high cell-density bioinks capable of forming complex multiphase constructs. Published in Materials Today, the study introduces a platform that combines individual or aggregate-based stem cell bioinks with localized growth factor delivery, offering precise control over spatial differentiation and tissue development.
Using a shear-thinning, photocrosslinkable alginate microgel supporting bath, the research team successfully printed structures with high shape fidelity and tunable degradation. These constructs enable self-assembly through cellular condensation and localized differentiation into distinct tissues such as cartilage and bone. After four weeks of culture, the bioprinted structures maintained their original geometry and exhibited clear phase separation between chondrogenic and osteogenic regions.
A new approach to bioink precision
Conventional bioprinting approaches often rely on biomaterial-laden inks that can interfere with direct cell–cell interactions and degrade unpredictably. To overcome these limitations, the researchers developed bioinks containing either individual stem cells or multicellular aggregates, combined with gelatin microparticles (GMs) loaded with growth factors such as TGF-β1 and BMP-2.
These formulations demonstrated favorable rheological properties, shear-thinning, self-healing, and low yield stress, making them well-suited for extrusion-based bioprinting. Critically, the growth factor-loaded GMs allowed for spatially controlled, sustained biochemical signaling without requiring external supplementation.
Following 3D printing and stabilization of the supporting bath, stem cells underwent lineage-specific differentiation, resulting in stable osteochondral constructs. Histological and biochemical analyses confirmed targeted extracellular matrix deposition and distinct tissue boundaries at the cartilage–bone interface.
From biomaterials to biofunction
While 3D bioprinting has long promised the recreation of complex biological architectures, printing functional, multicellular, multi-tissue constructs remains a key challenge. Cell-only bioinks often require preformed strands or aggregates, limiting resolution and design flexibility. The approach developed by Jeon et al. addresses this gap, enabling high-resolution deposition of cell-dense bioinks that self-organize into biologically relevant structures.
Recent innovations have similarly advanced bioink design and tissue engineering. Researchers at Seoul National University of Science and Technology, developed a SCOBY-derived bioink to 3D print cellulose scaffolds for direct tissue repair, while another team created a personalized heart-on-a-chip using photopolymerizable, patient-specific bioinks. Bio INX and Readily3D launched a ready-to-use bioink for volumetric bioprinting, and Texas A&M engineered a specialized vascular-specific bioink tailored for blood vessel formation. Elsewhere, studies have demonstrated functional brain tissue constructs with active neural networks, and Frontier Bio received a 2024 3DPI Award for developing lung-like tissue in vitro.
Jeon et al.’s work builds on these efforts by integrating localized growth factor delivery into high cell-density bioinks, enabling the fabrication of multiphase tissues with fine spatial control and biological fidelity.
By controlling the spatial presentation of bioactive cues within densely cellular environments, the platform holds promise for regenerative medicine, disease modeling, and drug screening. Future research will aim to enhance tissue maturation and incorporate vascularization to improve functionality and translational potential.
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