High Strength Brushite Bioceramics by Selective Regulation with Chiral Biomolecules

In biomineralization, biological molecules guide the formation and organization of inorganic crystals to construct materials that have exceptional mechanical properties. In Nature, these biomolecules are homochiral, composed exclusively of L-amino acids. Here, we show that chiral tartaric acid can improve the mechanical properties of a calcium-phosphate bioceramic by regulating its crystal structure. The mechanical properties of brushite bioceramic were improved by the addition of L-(+)-tartaric acid, which decreased crystal size, with this relationship following the classic Hall-Petch strengthening effect; D-(-)-tartaric acid had the opposite effect. Characterization of brushite crystals from the macro- to the atomic-level revealed that this regulation is attributable to a stereochemical matching between L-(+)-tartaric acid and chiral steps of brushite crystals, which results in inhibition of brushite crystallization. These findings provide insight into understanding the role of chiral L-biomolecules in biomineralization, and how bioceramics can be fabricated with a controlled crystallographic structure that defines high-performance mechanical properties.