Mechanically robust egg white protein hydrogels enabled by succinylation-assisted cyclic mineralization.

Constructing natural protein hydrogels with controllable structures and high stability remains a major challenge in sustainable material development. In this study, egg white protein (EWP) was used as a model to develop a succinylation-assisted cyclic mineralization strategy, in which regulated protein-ion coordination reinforced the hydrogel network. Succinylation markedly increased surface charge density and ion-binding capacity, enabling controlled in situ calcium phosphate deposition during alternating Ca2+/HPO42- immersion cycles. As mineralization progressed, the inorganic content increased from 26.71% to 57.96%, and the Ca/P ratio rose from 0.5 to 1.61. Under moderate mineralization conditions, the hydrogels exhibited a denser microstructure with significantly enhanced gel strength and hardness, accompanied by reduced swelling. Spectroscopic and microscopic analyses revealed mineralized domains rich in amorphous calcium phosphate or poorly crystalline apatite. Molecular docking and molecular dynamics simulations indicated that succinylation increased protein conformational flexibility, thereby strengthening Ca2+/HPO42- coordination. Notably, the optimized hydrogels showed good cytocompatibility and significantly upregulated osteogenic marker gene expression in MC3T3-E1 preosteoblast cells. This strategy provides an effective route for regulating structure-property relationships in egg white protein hydrogels.