Granular hydrogels are an exciting class of microporous and injectable biomaterials that are being explored for many biomedical applications, including regenerative medicine, 3D printing, and drug delivery. Granular hydrogels often possess low mechanical moduli and lack structural integrity due to weak physical interactions between microgels. This has been addressed through covalent inter‐particle crosslinking; however, covalent crosslinking often occurs through temporal enzymatic methods or photoinitiated reactions, which may limit injectability and material processing. To address this, a hyaluronic acid (HA) granular hydrogel is developed with dynamic covalent (hydrazone) inter‐particle crosslinks. Extrusion fragmentation is used to fabricate microgels from photocrosslinkable norbornene‐modified HA, additionally modified with either aldehyde or hydrazide groups. Aldehyde and hydrazide‐containing microgels are mixed and jammed to form adhesive granular hydrogels. These granular hydrogels possess enhanced mechanical integrity and shape stability over controls due to the covalent inter‐particle bonds, while maintaining injectability due to the dynamic hydrazone bonds. The adhesive granular hydrogels are applied to 3D printing, which allows the printing of structures that are stable without any further post‐processing. Additionally, the authors demonstrate that adhesive granular hydrogels allow for cell invasion in vitro. Overall, this work demonstrates the use of dynamic covalent inter‐particle crosslinking to enhance injectable granular hydrogels.
The incorporation of a secondary network into traditional single‐network hydrogels can enhance mechanical properties, such as toughness and loading to failure. These features are important for many applications, including as biomedical materials; however, the processing of interpenetrating polymer network (IPN) hydrogels is often limited by their multistep fabrication procedures. Here, a one‐pot scheme for the synthesis of biopolymer IPN hydrogels mediated by the simultaneous crosslinking of two independent networks with light, namely: i) free‐radical crosslinking of methacrylate‐modified hyaluronic acid (HA) to form the primary network and ii) thiol–ene crosslinking of norbornene‐modified HA with thiolated guest–host assemblies of adamantane and β‐cyclodextrin to form the secondary network, is reported. The mechanical properties of the IPN hydrogels are tuned by changing the network composition, with high water content (≈94%) hydrogels exhibiting excellent work of fracture, tensile strength, and low hysteresis. As proof‐of‐concept, the IPN hydrogels are implemented as low‐viscosity Digital Light Processing resins to fabricate complex structures that recover shape upon loading, as well as in microfluidic devices to form deformable microparticles. Further, the IPNs are cytocompatible with cell adhesion dependent on the inclusion of adhesive peptides. Overall, the enhanced processing of these IPN hydrogels will expand their utility across applications.
more » « less- Award ID(s):
- 1720530
- PAR ID:
- 10368892
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 34
- Issue:
- 28
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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