Induction of Circular Patterns of Calcium Oxalate Monohydrate on Mica-Supported Defective Monolayer Films of Dipalmitoylphosphatidylcholine

Abstract

Fluorescence microscopy and atomic force microscopy were used to observe the microstructures of liquid condensed (LC) domains and liquid expanded (LE) phases in monolayers of dipalmitoylphosphatidylcholine transferred to a mica surface after treatment by potassium oxalate (K2C2O4). The orderly molecular arrays in the monolayers were destroyed by K2C2O4, especially at the LC/LE boundaries. As a result, circular defective domains were formed. Scanning electron microscopy results showed that the defective domains could induce the formation of circular patterns of calcium oxalate monohydrate (COM) crystals. As the concentration of K2C2O4 [c(K2C2O4)] increased from 0.3 to 5.0 mmol/L, the effect of K2C2O4 on the monolayers was gradually strengthened. The monolayers treated by 0.3 mmol/L K2C2O4 induced solid circular patterns of COM crystals; that is, the COM crystallites were compactly arrayed in the domains. When c(K2C2O4) was increased to 5.0 mmol/L, the patterns turned to a ring shape; that is, there were crystals only at the LE/LC boundaries, few crystals were found in the center of the domains, and the number of small patterns with a diameter of less than 20 μm increased remarkably. Using the defective monolayers as a model, it is helpful to understand the relationships between urolithiasis and the injury of renal epithelial membrane at the molecular level and to biomimetically synthesize advanced materials by using organic templates.