Injectable Macroporous Hydrogel Formed by Enzymatic Cross-Linking of Gelatin Microgels

Abstract

Injectable hydrogels can be useful tools for facilitating wound healing since they conform to the irregular shapes of wounds, serving as a temporary matrix during the healing process. However, the lack of inherent pore structures of most injectable hydrogels prohibits desired interactions with the cells of the surrounding tissues limiting their clinical efficacy. Here, we introduce a simple, cost-effective and highly biofunctional injectable macroporous hydrogel made of gelatin microgels crosslinked by microbial transglutaminase (mTG). Pores are created by the interstitial space among the microgels. A water-in-oil emulsion technique was used to create gelatin microgels of an average size of 250μm in diameter. When crosslinked with mTG, the microgels adhered to each other to form a bulk hydrogel with inherent pores large enough for cell migration. The viscoelastic properties of the porous hydrogel were similar to those of nonporous gelatin hydrogel made by adding mTG to a homogeneous gelatin solution. The porous hydrogel supported higher cellular proliferation of human dermal fibroblasts (hDFs) than the nonporous hydrogel over two weeks, and allowed the migration of hDFs into the pores. Conversely, the hDFs were unable to permeate the surface of the nonporous hydrogel. To demonstrate its potential use in wound healing, the gelatin microgels were injected with mTG into a cut out section of an excised porcine cornea. Due to the action of mTG, the porous hydrogel stably adhered to the cornea tissue for two weeks. Confocal images showed that a large number of cells from the cornea tissue migrated into the interstitial space of the porous hydrogel. The porous hydrogel was also used for the controlled release of platelet-derived growth factor (PDGF), increasing the proliferation of hDFs compared to the nonporous hydrogel. This gelatin microgel-based porous hydrogel will be a useful tool for wound healing and tissue engineering.

Designing Microgels for Cell Culture and Controlled Assembly of Tissue Microenvironments

“…[116,130] Creating easily manipulatable formulations is important for biological applications, as they can be used to create injectable or moldable scaffolds. [34,131,132] While the vast majority of previous injectable formulations have been nonporous and have relied on degradation rates to allow for cell infiltration, the inherent porosity in microgel assembled scaffolds could allow for improved formulations and rapid tissue regeneration. Importantly, microgel assembly and cross-linking can be tailored to specific cell types and applications.…”

A multi-interpenetrating network (IPN) hydrogel with gelatin and silk fibroin

“…In order to enhance the mechanical properties, two layers of IPNs were formed in the hydrogel successively. Gelatin was chosen due to its ready-availability and its excellent bioactivity, which allows cell adhesion and proliferation without addition of external cell adhesive ligands 28,29 . Silk fibroin was chosen because of its excellent mechanical properties and proven biocompatibility 30,31 .…”

Granular Cellulose Nanofibril Hydrogel Scaffolds for 3D Cell Cultivation

“…A number of other approaches have also been developed, including the generation of microporous hydrogels through the use of phase separation during the crosslinking of poly(ethylene glycol) in the presence of highly viscous polysaccharides under physiological conditions, [11] incorporation of biocompatible porogen beads resulting in void forming hydrogels, [12] colloidal-crystal templating techniques, [13] or enzymatic assembly of spherical microgels. [14][15][16][17][18][19] Spherical microgels can be functionalized with fibrin-derived peptides, allowing for subsequent enzymatic crosslinking between them. Alternatively, physically assembled microgels can be crosslinked through exposure to UV light [20] and microgels can also be assembled by harnessing dynamic ionic interactions.…”