Permeability mapping of gelatin methacryloyl hydrogels.

We report the development of an efficient, customized spherical indentation-based testing method to systematically estimate the hydraulic permeability of gelatin methacryloyl (GelMA) hydrogels fabricated in a wide range of mass concentrations and photocrosslinking conditions. Numerical simulations and Biot's theory of poroelasticity were implemented to calibrate our experimental data. We correlated elastic moduli and permeability coefficients with different GelMA concentrations and crosslinking densities. Our model could also predict drug release rates from the GelMA hydrogels and diffusion of biomolecules into the three-dimensional GelMA hydrogels. The results potentially provide a design map for choosing desired GelMA-based hydrogels for use in drug delivery, tissue engineering, and regenerative medicine, which may be further expanded to predicting the permeability behaviors of various other hydrogel types. STATEMENT OF SIGNIFICANCE: GelMA hydrogels have attracted increasing attention in recent years as matrices for cell cultures and biomolecule delivery. This inexpensive polymer is derived from gelatin functionalized with methacryloyl groups that can be crosslinked by photochemical reactions. Here we report the development of an efficient, customized testing method to systematically estimate the hydraulic permeability of GelMA hydrogels. Hydraulic permeability indicates the resistance of GelMA hydrogels to the movement of saturated fluid. We used the model to measure the elastic moduli and permeability coefficients, providing a permeability map for various GelMA hydrogel formulations.