Anionic polysaccharides mixture control the assembly of nanoscale building blocks of calcium carbonate into hierarchical spherical and rod-shaped mesocrystals.

Biominerals, as complex organic-inorganic nanocomposites synthesized by organisms, exhibit unique properties across various scales. This study investigates the role of soluble organic molecules, specifically acidic polysaccharides such as N-carboxymethyl chitosan (CMC) and chondroitin 6-sulfate (ChS), in regulating the formation of calcium carbonate mesocrystals. Using a precipitation method, the effects of these polymers on the morphology, size, and polymorphism of mesocrystals were evaluated. The findings reveal that the interactions between calcium carbonate and the polymers dictate the morphology of primary nanoparticles, which subsequently assemble into spherical or rod-shaped mesocrystals. Carboxylated polymers were found to stabilize the vaterite phase, while sulfated polymers favored calcite formation. By fine-tuning the polymer quantities, addition rate, and mixing technique, the size and aspect ratio of the mesocrystals can be precisely controlled, enabling targeted morphogenesis. This strategy not only advances the design of tailored mesocrystals but also deepens our understanding of nonclassical crystallization processes mediated by soluble organic biomacromolecules.