The co-effect of organic matrix from carp otolith and microenvironment on calcium carbonate mineralization.

In vitro mineralization experiment is an effective way to study the effect of organic matrix on calcium carbonate crystallization, and to reveal the relationship between organic matrix and inorganic crystal in natural biominerals. In natural biominerals, organic matrix plays an important role in crystal formation and stability, together with microenvironment changes, they can affect crystal polymorph, morphology, density, size, orientation etc. In this work, we systematically studied the effects of different organic matrices in fish otoliths, the organic matrix concentration changes, as well as the co-effect of organic matrices with temperature, pH value and Mg ion changes in the in vitro CaCO3 mineralization experiments. The organic matrix and concentration change experiments prove that water soluble matrix (WSM) plays an important role in crystal form transition. It can induce CaCO3 crystals with same crystal polymorph as the otolith from which organic matrix was extracted. The temperature change experiment proves that CaCO3 has a tendency to form calcite, vaterite, and then aragonite in priority as temperature goes up. Under different temperature, WSM from lapillus/asteriscus still has the effect to mediate different CaCO3 crystals. The pH change experiment shows that, near the neutral environment, as pH value goes up, calcites have a tendency to form crystal aggregates with more faces exposed, the organic matrix still keeps crystal mediation effect. The Mg(2+) experiment shows that, Mg ion can promote aragonite formation, together with lapillus organic matrix, aragonites with different shapes are formed.