Diffusion-Limited Growth of Calcium Phosphate for Macroscale Fabrication of Mineralized Gelatin Hydrogels

This study investigates the impact of a cationic polymer, polyethylenimine, on calcium phosphate mineralization within a gelatin hydrogel, aiming to enhance biomaterial design. The adjustment of polyethylenimine concentrations in gelatin hydrogels results in spatially selective and continuous mineralization, transitions from periodic Liesegang patterns to denser, more continuous formations, and influences the morphology of precipitates. Based on the simulation, it was found that continuous mineralization could be achieved by decreasing the diffusion coefficient of intermediates. It is counterintuitive because it has been widely known that surface-only or periodically patterned crystallization is caused by the slow diffusion of substances in a hydrogel. The mechanism of continuous mineralization has been proposed by distinguishing the effects of cationic and anionic polymers on the mineralization processes. The results suggest that cationic polymers could be leveraged to develop advanced biomaterials requiring precise control of mineral deposition and structural integrity, particularly for bone regeneration and repair applications.