Silk Fibroin‐Regulated Crystallization of Calcium Carbonate

Abstract Mollusk shell is one of the best studied of all calcium carbonate biominerals. Its silk‐like binder‐matrix protein plays a pivotal role during the formation of aragonite crystals in the nacre sheets. Here, we provide novel experimental insights into the interaction of mineral and protein compounds using a model system of reconstituted Bombyx mori silk fibroin solutions serving as templates for the crystallization of calcium carbonate (CaCO₃). We observed that the inherent (self‐assembling) aggregation process of silk fibroin molecules affected both the morphology and crystallographic polymorph of CaCO₃ aggregates. This combination fostered the growth of a novel, rice‐grain‐shaped protein/mineral hybrid with a hollow structure with an aragonite polymorph formed after ripening. Our observations suggest new hypotheses about the role of silk‐like protein in the natural biomineralization process, but it may also serve to shed light on the formation process of those ‘ersatz’ hybrids regulated by artificially selected structural proteins.