Systematic comparisons of preparative protocols to generate various types of stone-related crystals for in vitro study of renal calculi

In vitro studies of stone-related crystals and crystals-cell interactions have been extensively done to investigate cellular, molecular and pathogenic mechanisms leading to renal calculi. Effective preparation of various types of stone-related crystals is thus crucial for such studies. Nevertheless, various protocols for preparing these stone-related crystals were scatteredly reported without comparative analysis of their efficacies and yields. Herein, we systematically compared our protocols (with the suffix “-Si”) for preparing calcium oxalate (CaOx) monohydrate (COM), CaOx dihydrate (COD), magnesium ammonium phosphate (struvite), uric acid (UA), calcium phosphate dihydrate (brushite), hydroxyapatite (HAP), and calcium carbonate (CaCO₃) crystals with other protocols published previously. The morphological evaluation revealed that our protocols provided the most homogeneous and most typical monoclinic prismatic, bipyramidal, coffin lid and rectangle shapes of COM, COD, struvite and UA crystals, respectively. There were comparable morphological results for brushite, HAP and CaCO₃ crystals generated by different protocols. Our protocols provided the greatest yield for generating brushite crystals but with lower yields for others. Chemical analysis by Fourier transform infrared (FTIR) spectroscopy revealed comparable results among different protocols to generate each crystal type. In summary, all these protocols can be used to generate each crystal type. But our protocols offer the best quality, in terms of homogeneity and typical shape, for generating COM, COD, struvite and UA crystals.