Simulation And Inhibition Of Calcium Oxalate Urinary Stone In Vitro

Urinary stone is the product of abnormal biomineralization in vivo. It is a kind of disease in urinary system. Urinary stone is composed of organic matrices containing polysaccharide, protein and inorganic salts, such as calcium oxalate (CaC₂O₄), especially calcium oxalate monohydrate (COM) crystal. Researchers have found the ringed homocentric structures in the section of urinary stone, but the formation mechanism remains unclear. Therefore, in this paper, polysaccharide-agar gel system is used as a template to study the growth of CaC₂O₄ crystal and the formation of periodic ringed precipitation in agar gel systems.The paper is separated into four parts that are shown as follows:1. The growth of CaC₂O₄ crystals was studied in one dimension agar gel system and the crystals were characterized using XRD and FT-IR spectra. The results show that there were lamellar, rod and sphere-like CaC₂O₄ hydrate in the gel. The content of triclinic trihydrate (COT), which was most unstable in normal condition, was the highest while the content of tetragonal dihydrate (COD) was the lowest in the gel. Those suggest that agar system diminished interfacial energy, offered nucleation site, and promoted heterogeneous nucleation of crystal and growth of high-energy crystal.2. Influences of different ligands including some biomolecules on crystallization of calcium oxalate were studied in the CaC₂O₄-agar two-dimensional disc system. A mixture of calcium oxalate monohydrate (COM), calcium oxalate dihydrate(COD) and COT were obtained in the absence of ligands, and the content of COM was higher. All the three crystal forms, i.e., COM, COD and COT, were obtained in the presence of phytic acid, uric acid and aspartic acid, but the content of COM decreased apparently. The mixture of COT and COD occurred in the two-dimensional system containing sodium citrate, EDTA and dextrose, the formation of COM was inhibited. The experiment results suggest that all the ligands mentioned above can inhibit effectively the formation of COM in the CaC₂O₄-agar two-dimensional gel system.3. Influences of rare earth ions (La3+, Pr3+, Nd3+Gd3+, Tb3+ and Er3+) on crystallization of calcium oxalate and the fonnation of periodic ringed precipitation were studied in the two-dimensional agar gel system. Meanwhile, the structures and the properties of the crystals were characterized by XRD and FT-IR. The results show that light and heavy rare earth ions all can promote the fonnation of periodic ringed precipitation in the above system. The formation time, the size and the number of rings changed with the concentration and radius of rare ions. It demonstrates rare ions can promote the formation of periodic ringed precipitation. Rare ions are similar to Ca2+ in the property and have strong coordination with oxo-ligand, so they may exist in the periodic ringed precipitation. In addition, it was found that the fonnation of COM was promoted by the addition of Er3+and inhibited by the addition of Nd3+ and La3+. The formation mechanism of periodic ringed precipitation was discussed.4. Influences of transition metal ions and Li+ on crystallization of calcium oxalate and the formation of periodic ringed precipitation were investigated in the two-dimensional agar gel system. The results indicate that periodic ringed precipitation produced with a certain concentration of Fe3+, and the formation of COM was inhibited. In addition, the main crystal form is COD in the gel with Zn2+, Co2+, Ni2+ and U+, while COT in the gel with Cu2+. These results show that different metal ions had different influence on the crystallization of CaC2O4. Furthermore, the special phenomena in agar gel which was similar to the blaze and the radial stripe in urinary Stone were discussed.