Photocrosslinkable Hydrogel Microparticle Bioink for Digital-Light-Processing 3D Bioprinting

Digital light processing (DLP) 3D bioprinting is a powerful technique for fabricating intricate tissue structures, yet it faces challenges related to limited bioink selection, difficulty in printing heterogeneous materials, and poor cell incorporation. In this study, photocrosslinkable hydrogel microparticle (HMP) bioinks tailored for DLP bioprinting are developed and optimized. Unlike traditional extrusion-based printing of HMPs that rely on jamming, the DLP approach eliminates this constraint, enabling improved printing resolution and cytocompatibility. It is demonstrated that the aqueous components, such as crosslinkers and photoinitiators, mixed in HMP bioinks ensure sufficient fluidity, supporting consistent DLP printing across a broad range of parameters. Small HMPs (28.2 ± 1.78 µm) provided better structural fidelity than large HMPs (75.0 ± 4.73 µm). Optimized crosslinking conditions and finely tuned UV exposure settings further enabled high-resolution printing, including the formation of serpentine inner channels. Importantly, cell-laden HMP bioinks maintained high viability, achieved uniform cell distribution within printed constructs, and supported their continued growth due to the void spaces between HMPs. The modular nature of HMPs also allowed straightforward multi-material printing. This work expands the application of HMP bioinks to DLP bioprinting, offering a versatile platform for biomanufacturing tissue constructs with microscopic compartmentalization for tissue engineering applications.