Counter-Diffusion System As An In Vitro Model In The Investigation Of Proteins Involved In The Formation Of Calcium Carbonate Biominerals

Mineralization in living organisms is highly regulated by the synergistic action of many macromolecules, where distinctive proteins play the role of direct modulators of the crystal growth. The number of methods for in vitro biomineralization studies in the presence of proteins is limited due to the influence of the environment on their functionality. We focus on a counter-diffusion system in the biomineralization of calcium carbonate that is based on the diffusion of salt solutions through a gel-matrix supplemented with the protein of interest. This article discusses the background of the system, physical principles, matrices commonly in use, advantages, limitations, variations, and our own experience. Special attention is paid to the overview of already published studies that applied the counter-diffusion system as a model for investigation of the biomineralization of calcium carbonate. The system has great potential to be widely used in the analysis of biomineralization-associated proteins in vitro and the biomineralization process itself. This perspective recalls the most important theoretical basis as well as practical application of the system for specialists in various fields of biomineralization.