Gelatin-based materials with inverse structures: Porous hydrogels compared to hydrogel particles

In this study, we synthesized two different gelatin methacryloyl (GelMA) hydrogels with inverse macroscopic structures and similar hydrogel network structures, i.e. porous hydrogels and hydrogel particles. Inverse macroscopic structures means that the node size of the porous hydrogels equals the diameter of the hydrogel particles. The goal is to design materials with same transport properties but different macroscopic structures. We generated porous hydrogels and hydrogel particles by using microfluidic-based liquid foam and droplet templating. For this purpose, we developed formulations containing a highly modified GelMA (GM10) to obtain hydrogel precursor solutions with low viscosity and high crosslinking ability. Porous hydrogels and hydrogel particles with monodisperse pore and particle sizes, respectively, were obtained. Via X-ray microtomography, we investigated the macroscopic structure and found the size range to generate porous hydrogels and hydrogel particles with inverse macroscopic structures. In addition, similar surface-to-volume ratios for both hydrogels were found. The similarity of the hydrogel network structures of both hydrogels was shown by measuring the equilibrium degree of swelling (EDS) in two different swelling media. Cytotoxicity assays confirmed the cytocompatibility of both hydrogels. These findings establish a foundation for future studies on drug sorption and release of these two hydrogel materials.