Crystallization of calcium oxalate beneath Langmuir monolayers in the presence of urinary inhibitors

The crystallization of calcium oxalate (CaOxa) beneath Langmuir monolayers of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) was investigated by environmental scanning electron microscopy (ESEM) and X-ray diffraction (XRD) analysis. The headgroups of the monolayer materials, the surface pressure of the monolayers and the biomolecules in subphases affected the formation of CaOxa crystals. More calcium oxalate monohydrate (COM) crystals were observed beneath SA monolayers than that beneath DPPC monolayers. The crystals grown at SA monolayers exhibited unusual morphology, while beneath DPPC monolayers the COM crystals were oriented with the elongated hexagonal face parallel to the plane of the monolayers. More crystals were observed at lower surface pressure of DPPC monolayers. In the presence of l-glutamic acid (l-glu), irregular polyhedron crystals and three-dimensional hexagonal prismatic crystals were obtained. While urinary macromolecule chondroitin sulfate A (C4S) made the elongated (1¯01) face of COM much longer and the crystals became thinner. C4S can also delay the two-dimensional (2D) growth of the (1¯01) face of COM crystals.