Selective mineralization at hydrogel interface induced by fusion between peptide hydrogels†

Biomineralization has garnered attention not only for its fundamental role in understanding the mechanisms of biomineral formation but also as a method for fabricating next-generation functional materials. In this study, we investigated the nucleation, crystal growth, and particle growth processes of calcium phosphates (CaPs) formed using selective mineralization at the hydrogel interface induced by the fusion of peptide hydrogels. After 1 day of mineralization, band-like white precipitates were observed at the fusion interface of the hydrogels. Notably, the nucleation and crystal growth of the mineralized CaP exhibited different behaviors owing to the differences in the properties of the reaction interface for mineralization. The selective nucleation and crystal growth of the CaPs at the hydrogel interface were attributed to (1) the local concentration of mineral sources near the peptide network, driven by electrostatic interactions between the polar functional groups and mineral source ions, and (2) selective crystal growth of the CaPs induced by the nanostructure of the surface functional groups.