Studies On The Biomineralization Of Calcium Oxalate Crystals Induced By Organized Molecular Films

Studies on the biomineralization of calcium oxalate crystals were performed in vitro using monolayer film and Langmuir-Blodgett film as templet. SEM, ESEM, TEM, AFM, XRD and FT-IR were used to characterize calcium oxalate crystals obtained from a series of experiments.The monolayer which was composed of different materials had different effect on the formation of calcium oxalate crystals at the interface of monolayer/water. The growth of COM crystals at stearic acid monolayer was regular and both end of the crystals became sharp angles because stearic acid molecular has negative group. The crystals beneath DPPC monolayers were oriented with the elongated hexagonal ( 101 )face paralleled to the plane of the monolayer and smaller than those from bulk solution.Chondroitin sulfate A (C4S), as a kind of endogenetic urinary macromolecule, not only increased the supersaturation of CaC2O4 in solution, but also inhibited the two-dimensional growth and aggregation of COM crystals.The growth of calcium oxalate crystals was influenced by surface pressure beneath DPPC monolayer film. There were some crystals which have the same appearance as COM crystals obtained from pure water system when monolayer surface pressure was hold 1,10 and 30 mN/m while those growth at 20 mN/m were perfect orderly induced by DPPC monolayer. It was also indicated that DPPC monolayer had distinctly effect on the initial nucleation of COM crystals through the examination by TEM.Under DPPC monolayer, the appearance of COM was also different when different additives were added to subphases. C4S made the elongated (101) crystal face longer and the crystals become thinner while cattle serum albumen only made COM become thinner. L-glutamic acid, one of amino residues, increased the edges and corners of COM crystals.The LB films of DPPC were also used to study the growth of calcium oxalate crystals. It was found that calcium oxalate crystals nucleated on the domain boundaries by AFM observation. The morphology of COM was also influenced by the additives of C4S and L-Glu. As increasing the concentration of C4S, the amount of COM crystals with a hexagonal prism decreased and that with a thin hexagonal slice increased. When the concentration of C4S was 0.50 mg/mL, all the calcium oxalate crystals were thin hexagonal slice COM crystals. However, as the concentration of L-Glu increased from 0.01 to 0.50 mmol/L, the hexagonal prism-like COM crystals gradually transformed to COM crystals with one or two (010) crystal face disappearance.There were some shortcomings in the present experiments as investigating the formation of urinary stone because the biologic membrane is mixed protein phospholipid monolayers and the system in which urinary stone formed in vivo is fluid. If the mixed films were used to study the formation of calcium oxalate crystals in fluid subphase, we can further understand the mechanisms of the formation of calculus crystallite at the cellular surface of urinary tract.