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

Abstract

Abstract3D 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.

Physically and Chemically Crosslinked Hyaluronic Acid-Based Hydrogels Differentially Promote Axonal Outgrowth from Neural Tissue Cultures

“…For the fabrication of chemically crosslinked HA-based hydrogels, aldehyde-modified HA (HA-CHO) and cysteine-modified HA (HA-CYS) with a ≈10% degree of modification were dissolved separately in PBS for 1–2 h. The pH of the dissolved components was precisely adjusted to approximately 7.4 using 0.1 mL NaOH. Subsequently, the two solutions were combined in a 1:1 ratio, initiating the formation of the thiazolidine-crosslinked hydrogel through the reaction between the cysteine (CYS) and aldehyde (CHO) functionalities [ 13 ].…”

“…The hydrogel obtained from covalent crosslinking employed thiazolidine linkages between HA-chains, distinguishing it from the other two biomaterials that were commercially procured with physical entanglement between chains. We have recently demonstrated the unique properties of thiazolidine-based HA hydrogels, showcasing their ability to enhance cell proliferation and exhibit prolonged stability compared to dynamically covalent crosslinked HA hydrogels [ 13 ]. The thiazolidine-linked HA hydrogel has a rapid gelation rate, making it particularly well suited to efficient cell encapsulation applications.…”

Recent Progress in 3D Printing of Polymer Materials as Soft Actuators and Robots

“…7 In contrast, photocuring printing, especially voxel printing achieved by precise light source control, offers high precision and efficiency and favors printing more complex structures. 3,55,61,62 The most widely used hydrogel systems for printed soft actuators and robots include polyacrylic acid (PAAc) gels, 62 polyacrylamide (PAAm) gels, 55 poly(N-isopropylacrylamide) (PNIPAm) gels, 60,63 hyaluronic acid gels, 63 chitosan gels, 64 and alginate gels. 65 According to the mechanical properties and responsiveness of hydrogels, hydrogel actuators or robots can be divided into three categories with different actuation principles: externalpressure-driven actuation, solvent swelling actuation, and matrix stimulus response actuation.…”

“…The ink for extrusion-based printing should have shear-thinning behavior or sol-gel transition, which can be achieved through solvent exchange, charge shielding, temperature variation, and post-curing. − While extrusion-based printing has been extensively used in various hydrogel systems, it suffers low printing efficiency, relatively poor accuracy, and challenges in printing small and high-precision structures . In contrast, photocuring printing, especially voxel printing achieved by precise light source control, offers high precision and efficiency and favors printing more complex structures. ,,, The most widely used hydrogel systems for printed soft actuators and robots include polyacrylic acid (PAAc) gels, polyacrylamide (PAAm) gels, poly­( N -isopropylacrylamide) (PNIPAm) gels, , hyaluronic acid gels, chitosan gels, and alginate gels …”

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine

“…In addition to plant-based components, hyaluronic acid, a linear polysaccharide composed of repeating units of N -acetyl glucosamine and glucuronic acid, is extensively found in mammalian bodies. 143,144 Its ability to provide a highly hydrated environment and mimic extracellular matrix properties aids in maintaining normal cellular metabolism and enhancing wound healing. Jiang et al synthesized stretchable gels through energy-dissipative dynamic Schiff base crosslinking of glycosaminoglycan hyaluronic acid ( o -nitrobenzyl grafted hyaluronic acid) and elastin with radical polymerization of methacrylated gelatin, exhibiting potentials as substitutes for native elastic tissues with their stretchability (∼170% strain), toughness (∼45 kJ m −3 ), and printability.…”