Calcium Oxalate Crystallization At Defective Sites Of Langmuir-Blodgett Films

The circular patterns of calcium oxalate (CaOxa) crystals were first induced at defective sites of Langmuir-Blodgett film of dipalmitoylphosphatidylcholine (DPPC) injured by potassium oxalate. This model system might be used to mimic formation of calcium oxalate (CaOxa) stones at surface of damaged renal epithelial membranes, microcosmic structure of defective LB films in the points of molecular and supramolecular level and the circular patterns of CaOxa crystals which induced by defective LB films were observed by Atomic Force Microscope(AFM), Scanning electronic microscope (SEM) and X-ray diffraction (XRD).The defective LB film of DPPC which injured by potassium oxalate can induce a lot of ring-shaped and solid circular patterns of calcium oxalate monohydrate (COM) crystals, and the crystal is mainly in needle shape with a small part being in forms of hexagonal or quadrangle. By comparison, the LB films without oxalate pretreatment only induced randomly growth of hexagonal COM crystals. In 0.3 mmol/L calcium oxalate solution, the circular patterns induced by defective LB film can be observed in 20 minutes. However, conventional LB films crystalise until an hour later, in bulk solution needs 6 hours. So, the ability to induce COM is: defective LB film conventional LB films> bulk solution.The crystallization time has an apparent effect on the shape and quantity of circular patterns of COM. As crystallization time increases, ringy patterns of COM transfer into solid circular shape, and the ratios of Solid circle patterns in different sizes is increasing. The size of single COM crystal in the circle patterns enlarge evidently. The ratios of small size(5-20 μm) circle patterns multiply, and the medium size (20-50 μm) show slight change; however, the number of big size (>50μm) decrease.The concentration of potassium oxalate which injure LB films has an obvious effect to circular patterns of COM. With increasing the concentration of oxalate, the COM in circle patterns will become thinner and thinner. Gradually, the solid circle patterns in 0.3 mmol/L will become ringy patterns in 5.0 mmol/L. The number of COM in circle patterns is 0.3>0.6>2.5>5.0 . Meanwhile, the number of circle patterns increases, and its rule is 5.0>2.5>0.6>0.3.Increasing the time placed in desiccator, defective LB film can induce circular patterns of COM with many holes.The results would shed light on the molecular mechanism of structure change in renal epitheial membrane injured by oxalate at the molecular and supremolecular level, and on the relationship between urolithiasis and the injury of renal epitheial membrane.