Regulation Of Urinary Inhibitors Inhibitors On Calcium Oxalate Crystals Grown Beneath Langmuir Monolayers

Studies on the biomineralization of calcium oxalate (CaOxa) crystals were performed in vitro using monolayer film as model system at the presence of citric acid (H3cit), chondroitin sulfate A (C4S), chondroitin sulfate C (C6S) and serum albumin (CSA). Scanning electronic microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize CaOxa crystals obtained from a series of experiments.The nucleation and growth of calcium oxalate monohydrate (COM) crystals beneath stearic acid (SA) monolayers in the presence of H3cit was examined at different surface pressures (π). At the SA monolayers, the (101) faces of the COM crystals oriented towards the monolayer interface were remarkably stabilized independent of either the change in H3cit concentration from 0.01 to 0.30 mmol/L or the change in the π of the SA monolayer from 1 to 20 mN/m. However, the size of the COM crystals grown at low surface pressures (π= 1 mN/m) was larger and the crystals more ordered than those grown at high surface pressures. This result was due to a perfect match between the monolayer lattice and the crystal plane, and the monolayers at low surface pressure had a greater dynamic freedom and compressibility than those at high pressure to reorganize themselves in order to optimize the geometrical and stereochemical fit and then to accommodate the nucleating or growing crystals, H3cit can inhibit both the nucleation and growth of COM crystals at monolayers. Furthermore, H3cit can reduce the order of COM crystals grown at SA monolayers because H3cit disturbed the ordered array of the first layer of COM nuclei at the monolayer surface.The effect of urinary macromolecules such as C4S, C6S and CSA on CaOxa grown beneath dipalmitoylphosphatidylcholine (DPPC) monolayer was investigated. Only the COM was nucleated and grown beneath the monolayer with the (101) face oriented preferentially towards the monolayer interface. At the monolayer in the absence of additives, the tri-dimensional hexagonal prismy and tri-dimensional rhombus prismy COM crystals precipitated. However, the (101) face of COM was doubly strengthened and the other faces were weakened in the presence of C4S, C6S and CSA. This leaded to the formation of two-dimensional plate-like COM crystals. The result was attributed to the strong electrostatic interactions between the Ca2+-rich (101) crystal faces of COM and the polyanionic polysaccharide C4S, C6S and CSA together with the negatively charged sites of the zwitterionic DPPC monolayers. Thus resulted in remarkable preferential growth of the (101) faces.