Crystallization Of Calcium Oxalate In Different Mimetic Systems And Chemical Simulation On Urinary Calculi

The nucleation, growth and aggregation of the crystals of calcium oxalate (CaOx) were comparatively investigated in 5 different mimetic systems: aqueous solution, NaCl, artificial urine, diluted healthy urine and diluted lithogenic urine using scanning electron microscopy (SEM). The effects of original concentration of CaOx and crystallization time on the morphology, density and the size of CaOx crystals were discussed in detail. The original concentration of CaOx to obtain the largest crystals of COM in different systems depended on their properties. For the systems of NaCl, diluted healthy urine and diluted lithogenic urine, the concentrations were 0.60 mmol/L. However, the concentrations were 0.30 and 1.20 mmol/L in aqueous solution and artificial urine, respectively. The morphology of COM obtained in aqueous and NaCl solution was hexagon with tridimensional structure, however the morphology of COM in the artificial urine, diluted healthy urine and diluted lithogenic urine were equilateral hexagon, obtuse hexagon and acuminate hexagon, respectively.A mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) were obtained in diluted healthy urine. COD has a less affinity for renal tubule cell surface. So COD is easy to be expelled from body and there is a less probability of stone-forming in healthy urine. It indicated that there was more macromolecules inhibiting COM phase and promoting COD phase in healthy urine. But in the diluted lithogenic urine there obtained a mixture COM and Calcium oxalate trihydrate (COT) that was an unstable phase in thermodynamics. COT may be an important rapidly-converted precursor in the formation of certain renal stones. No remarkable effect of the crystallinic time was observed on morphology of COM in the diluted healthy urine. However, the crystal-size and density can be affected by the crystallinic time. In the early stage of crystallization (1~6 days) the sizes of COM crystals increased and the density of crystals changed little as increasing the crystallinic time due to growth control. In the middle and late stage (6-30 days) the number of crystals increased markedly while the growth rate changed little due to nucleation control. In the diluted lithogenic urine, the phases of crystal obtained changed gradually from a mixture of COM and COT to COM with crystallinic time increasing from 1,3 to 7 days.Influence of sodium citrate on crystallization of COM was studied in the diluted healthy urine and diluted lithogenic urine. Sodium citrate inhibited the nucleation of CaOx in the diluted healthy urine, and it changed the growth habit of COM obtained in the diluted lithogenic urine from preferentially resting on (010) faces to preferentially restingon(Toi) faces, the later was easy to be expelled from body.A preliminary study on the dynamics of CaOx crystallization was carried through using nano-meter-sizer instrument. It's suggested that there were more crystal seeds which can induce the crystallization of CaOx in the lithogenic urine than in the healthy urine, so as to increase the dangers of stone-forming.