Fine-tuning Dynamic Cross-linking for Enhanced 3D Bioprinting of Hyaluronic Acid Hydrogels

3D bioprinting of stem cells shows promise for medical applications, but the development of an efficient bioink remains a challenge. Recently, the emergence of dynamically cross-linked hydrogels has advanced this field to obtain self-healing materials. However, more advanced bioinks are needed that display optimum gelling kinetics, viscoelasticity, shear-thinning property, structural fidelity, and hold the printed structures sufficiently long enough that allow maturation of the new tissue. Here, a novel extracellular matrix-based bioink for human mesenchymal stem cells (hMSCs) is presented. Hyaluronic acid (HA) is modified with cysteine and aldehyde functional groups, creating hydrogels with dual cross-linking of disulfide and thiazolidine products. The investigation demonstrates that this cross-linking significantly improves hydrogel stability and biological properties. The bioink exhibits fast gelation kinetics, shear-thinning, shape-maintaining properties, high cell survival after printing with >2-fold increase in stemness marker (OCT3/4 and NANOG), and supports cell proliferation and migration. Disulfide cross-linking contributes to self-healing and cell migration, while thiazolidine cross-linking reduces gelation time, enhances long-term stability, and supports cell proliferation. Overall, the HA-based bioink fulfills the requirements for successful 3D printing of stem cells, providing a promising solution for cell therapy and regenerative medicine.