Versatile and Extendable Boronate-Based Tunable Hydrogel Networks for Patterning Applications

Abstract

Hydrogel patterning is an emerging area of interest and a valuable tool for studying cellular interactions. However, patterning of hydrogels is normally performed with photo-cross-linkable moieties, severely limiting the choice of materials that can be used. Dynamic covalent cross-linked systems show highly desirable properties as they can show covalent and noncovalent characteristics in response to different environmental conditions, therefore allowing for a potential switch in hydrogel properties. To expand the repertoire of materials suitable for hydrogel patterning, we report versatile pregel polymer networks comprising poly­(vinyl alcohol) cross-linked with PEG-diboronates cross-linkers at low ratios. These pregel networks are highly processable and extendable: they can be pulled up into thin strands and used for patterning of thin lines and exhibit both shear thinning and shear thickening properties. The pregels can be easily converted into a hydrogel state by pH adjustment and show clear antibacterial effects. Valuably, the pregels can be integrated into a 3D printing setup to print programmable lines and shapes and subsequently converted into patterned hydrogels. This study demonstrates that dynamic boronate networks can be tuned to exhibit different states and could offer alternate strategies and possibilities for hydrogel patterning applications.

Boronate Ester Hydrogels for Biomedical Applications: Challenges and Opportunities

“…However, their fast relaxation and lack of stability in culture medium usually do not allow them to maintain a predefined shape for extended periods of time. To take advantage of their extrudability, BE hydrogels have been combined with additional cross-linking strategies that allow for postprinting stabilization . For example, a study reported the association of alginate, which contains diol groups, with PBA-modified laminarin (a polymer extracted from brown algae) to produce a BE hydrogel that can be stabilized by ionic cross-linking with calcium ions .…”

“…To take advantage of their extrudability, BE hydrogels have been combined with additional cross-linking strategies that allow for postprinting stabilization. 188 For example, a study reported the association of alginate, which contains diol groups, with PBA-modified laminarin (a polymer extracted from brown algae) to produce a BE hydrogel that can be stabilized by ionic cross-linking with calcium ions. 189 For 3D printing, each printed hydrogel layer was sprayed with CaCl 2 allowing the authors to print an 8-layer construct (3.2 mm height, 10 mm diameter) without structural collapse.…”

Self-healing polymer design from dynamic B–O bonds to their emerging applications

“…This tunable and flexible system has the potential to be a handy tool for biological applications such as studying the cellular response to environmental changes and 3D printing applications. 125 Besides, Hsu and coworkers developed a 3D-printable and glucose-sensitive boronate ester hydrogel for the construction of constructs with vascular-like channels using a commercial 3D bioprinter. 126 In this system, the combination of a sacrificial boronate ester hydrogel and a non-sacrificial gel was required to fabricate a vascularized pattern in the construct.…”

“…15b). 125 The pre-gels were extendable and could be pulled into thin strands, which subsequently could be patterned into thin lines. The pre-gels were also capable to be integrated into hydrogel printing to create standing 3D structures.…”

Dynamic Grafting of Carboxylates onto Poly(Vinyl Alcohol) Polymers for Supramolecularly‐Crosslinked Hydrogel Formation

“…The reversibility of these bonds have resulted in the formation of hydrogel with good self‐healing property [5] . Furthermore, these boronate‐based systems can be pulled into thin strings and used for hydrogel printing [4e] . These dynamic covalent bonds have also been introduced due to their high stability, as well as reprocessability under specific conditions [6]…”