Properties of Calcium Carbonate Synthesized from a Bile Solution in the Presence of Amino Acids

This study deals with a search for relationships between the composition and properties of CaCO₃ in bile and amino acid concentrations in it. Twenty two calcium carbonate samples were synthesized in bile by varying the concentrations of the amino acids histidine (His), methionine (Met), arginine (Arg), and tryptophan (Trp). It was found by thermodynamic modeling that the introduction of amino acids increases the stability of bile due to the reduction of the mole fraction of free Ca²⁺ ions. The CaCO₃ content in the solid phase of the synthesized samples was determined; the maximum content was found for the samples obtained with Arg, and the minimum one, for those obtained with Met. The X-ray diffraction (XRD) analysis and Fourier transform IR spectroscopy studies showed that all the resulting powders were based on vaterite. For the amino acids Met and Arg, their stabilizing effect in relation to metastable aragonite was proved. Optical microscopy showed the presence of vaterite spherulites in all the resulting powders. It was established by photon correlation spectroscopy (PCS) that calcium carbonate microparticles with a radius of less than 10 μm are represented by three fractions. All the amino acids under study can be used as medicines for treatment and prevention of microcholelithiasis.