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

Abstract

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.