Simulation Of Biomineralization Of Calcium Oxalate In Different Systems In Vitro

The biomineralization of urinary crystals calcium oxalate (CaOxa) was investigated using scanning electron microscope (SEM), X-ray diffraction (XRD) and atom force microscope (AFM) in different simulation systems. These systems include NaCl solution, silicate gel, Langmuir monlayer and Langmuir-Blodgett(LB) film with defects etc.Firstly, the influence of urinary macromolecule mucin on the growth of CaOxa in NaCl solution was investigated. In the control systems without mucin, calcium oxalate monhydrate (COM) crystals appeared as polymorphs with its (010) crystal face preferential growth. However, in the presence of mucin both the size and number of COM crystals were decreased, and the intensity of the diffraction peak of (101) face was strengthened in the debt of (010) face of COM crystals. It indicated that mucin can inhibit the nucleation and growth of COM crystals as well as induce the (101) face of COM.Secondly, the effect of four kinds of phosphates on growth of CaOxa crystals in the sodium silicate hydrogel system was investigated. The ability both to induce calcium oxalate dihydrate(COD) and to inhibit the growth and aggregation of COM decreased in the order: Na5P3O10>Na4P2O7>>(NaPO3)6>Na3PO4. The ability increased accordingly with the increase of their concentrations. In addition, we found that the magnesium ions didn't have distinct influence on growth of CaOxa crystals in the hydrogel system.Thirdly, the effect of chondroitin sulfate A(C4S) on crystal faces of COM crystals induced by Langmuir monlayer of dipalmitoylphosphatidylcholine(DPPC) was investigated. Under control of DPPC monolayers and C4S, the (101 ) face of COM was doubly strengthened and the (010) face was doubly weakened. With the increase of the concentration of C4S, COM changes from the tri-demensional hexagonal prisms to the much elongated hexagonal slice crystals.Finally, the biomineralization of CaOxa crystals induced by the LB film with defects was investigated in vitro preliminarily in order to simulate the injured renal epithelial membranes. The result showed that the crystals preferentially nucleated at sites with defects. The defects could also facilitate crystal attachment. These findings suggested that the injury of renal epithelial membranes plays an important role in the formation of urinary calculus. Our work can provide a new conception for treatment of urolithiasis effectively.