Dynamic Coordination Chemistry Enables Free Directional Printing of Biopolymer Hydrogel

Abstract

Three-dimensional (3D) printing is a promising technology to develop customized biomaterials in regenerative medicine. However, for the majority of printable biomaterials (bioinks) there is always a compromise between excellent printability of fluids and good mechanical properties of solids. Three-dimensional printing of soft materials based on the transition from a fluid to gel state is challenging because of the difficulties to control such transition as well as to maintain uniform conditions three-dimensionally. To solve these challenges, a facile chemical strategy for the development of a novel hydrogel bioink with shear-thinning and self-healing properties based on dynamic metal–ligand coordination bonds is presented. The noncovalent cross-linking allows easy extrusion of the bioink from a reservoir without changing of its bulk mechanical properties. The soft hydrogel can avoid deformation and collapse using omnidirectional embedding of the printable hydrogel into a support gel bath sharing the same cross-linking chemistry. After combination with photoinitiated covalent cross-linking, it enables manufacturing of hydrogel structures with complex shapes and precise location of chemically attached ligands. Living cells can be entrapped in the new printable hydrogel and survive the following in situ photo-cross-linking. The presented printable hydrogel material expands the existing tool-box of bioinks for generation of in vitro 3D tissue-like structures and direct in vivo 3D printing.

Self‐Healing Silk Fibroin‐Based Hydrogel for Bone Regeneration: Dynamic Metal‐Ligand Self‐Assembly Approach

“…The gel was liquefied at a shear strain above ≈150%, indicated by storage modulus G′ < loss modulus G″ (Figure 4d). [52] The capacity of the instantaneous self-healing of HA-BP·CaP@mSF hydrogel after damage offers quick molding of the material in clinical practice. [36,51] Besides the great injectability, the shearthinning properties and instantaneous self-healing of SF-based hydrogel should be highly appreciated in 3D printing technologies because it can be easily extruded from a reservoir and the printed layers can bind to each other quickly.…”

Self‐Healing Supramolecular Hydrogels for Tissue Engineering Applications

“…These gels undergo dynamic chemical degradation while maintaining the bulk properties of the hydrogel and have been used primarily as self‐healing 3D cell culture substrates. These materials often exhibit slower reversibility than their supramolecular counterparts and can require the addition of a catalyst, but they have still been used for 3D printing as their shear‐thinning and self‐healing behavior makes them desirable candidates for extrusion‐based printing . Compared to permanently cross‐linked hydrogels, the incorporation of cells into dynamic hydrogels is relatively new, and work remains to be done toward the development of adaptable covalent hydrogels for tissue engineering.…”

Printability study of metal ion crosslinked PEG-catechol based inks

“…Cells seeded on the crosslinked materials were viable, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D (bio)printing, and enables straightforward adjustment of the printable formulation to meet application-specific needs.Włodarczyk-Biegun et al 2 dynamics by varying the metal ion or the pH of the system [3], leading to networks with adjustable mechanical properties [11]. Metal complexation is widely used in natural materials to tune mechanical strength of bulk and interface materials.…”

“…shear modulus, relaxation time) of the formed polymer network can be finely tuned by the type of metal ion and pH. [13,14] Only a few reports have exploited metal-ligand coordination complexes to obtain printable hydrogels [3,11,15]. The bisphosphonate-Ca 2+ interaction has been used to print bisphosphonate-functionalized hyaluronic acid (HA-BP) at pH 7 [11].…”

“…[13,14] Only a few reports have exploited metal-ligand coordination complexes to obtain printable hydrogels [3,11,15]. The bisphosphonate-Ca 2+ interaction has been used to print bisphosphonate-functionalized hyaluronic acid (HA-BP) at pH 7 [11]. The reversible gel composed of 2.7% w/v HA-BP and 200 mM CaCl 2 was printable and scaffolds with four layers, with strand diameter of ca.…”