Inter-prismatic matrix structure characterizationof mollusk shell and its effect on crystal formation

Mollusk biomineralization is an elaborate process in which cells, organic macromolecules, and calcium carbonate crystals are actively involved. Macromolecules (mainly are proteins and polysaccharide) act as a key role in regulating and limiting the size, orientation, polymorph and texture of inorganic phase. In this work, we focused on the inter-prismatic matrix of mollusk shell combining scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) analytical techniques with CaCO₃ recrystallization experiment to characterize its structure and effects on crystal formation. Our results show that the inter-prismatic matrix is not a sort of pure polymer, calcite nano-crystals are also located inside the inter-prismatic matrix. Interestingly, it seems that these nanocrystals have a preferred orientation, which means the inter-prismatic matrix do impose effect on the crystal formation. In vitro re-crystallization experiment using partially dissolved prismatic fragment as template indicates that the (104) faces of CaCO₃ micro-crystals are closely associated with the walls of inter-prismatic matrix. Furthermore, a possible growth mechanism of mollusk shell prismatic layer was proposed.