Crystallization of calcium carbonate mineral with hierarchical structures regulated by silk fibroin in microbial mineralization system

In this work, we provide a novel idea to introduce silk fibroin (SF) into the microbial mineralization system and study the mechanism of mineralization of calcium carbonate by changing the mineralizing time and SF concentration. CaCO3 superstructures with complex forms and hierarchical surface textures were obtained in the presence of SF as a crystal growth modifier in the microbial mineralization system. Moreover, with the prolonged reaction time, the shape of CaCO3 in the additive-free mineralized system changes from a rough spherical to a smooth one, and then to a complex cube-like crystals. Surprisingly, superstructures CaCO3 crystals with smooth hemispheres were obtained in low concentrations of SF. An emergent self-organization process and its combination with an aggregated mechanism have been proposed for the formation of the complex hemispherical superstructure with numerous fish-like flakes on the surface in high concentrations of SF. What's more, we found that high SF concentration is favorable for the formation of vaterite. The above results imply that the specific biomimetic synthesis strategy in the microbial mineralization system can provide a useful pathway to produce inorganic or inorganic-organic hybrid materials with a unique shape and specific textures.