Abstract
The search for an efficient drug or inhibitor in the formation process of kidney stones has been a promising research topic towards reducing the risks of the formation of disease. However, several challenges have been faced in investigating the most common constituents of kidney stones, calcium oxalate and its hydrate forms (COM, COD and COT). This study focuses on the preparation and structural characterization (TG, XRD, FTIR, SEM) of calcium oxalate hydrates in the presence of gallic acid (GA) and by varying operating parameters such as temperature (25 °C, 36.5 °C and 48 °C), pH (5.6, 6.5 and 7.5) and amount of added GA (ranging from 100 mg to 1000 mg). Response surface methodology was applied in order to evaluate the effects of operating parameters in the formation of COM and COD, and for the process optimization towards maximizing their content in samples. The results indicated that GA inhibited the formation of COM (0–100%) and promoted the formation of COD (0 ≤ 99%), while a medium pH and the amount of added GA showed a significant effect in the process of COD formation. In order to investigate the interactions established in the formation process and the possible adsorption between GA and the formed crystals, electrochemical measurements were performed.
Highlights
More than 70% of kidney stone patients suffer from urolithiasis induced by calcium oxalate stone formation, with calcium oxalate dihydrate (COD) as the most dominant crystal phase in healthy human urine, and calcium oxalate monohydrate (COM) as the most common present phase in diseased humans
Quantity of gallic acid varied from 100 mg to 1000 mg, pH value was in the range from 5.6 to 7.5 and the system was thermostated at three different temperatures: θ = 25 ◦ C, 36.5 ◦ C and 48 ◦ C
Total weight loss of the sample after heating up to 300 ◦ C was 21.84% demonstrating the presence of two crystalline water molecules in COD
Summary
More than 70% of kidney stone patients suffer from urolithiasis induced by calcium oxalate stone formation, with calcium oxalate dihydrate (COD) as the most dominant crystal phase in healthy human urine, and calcium oxalate monohydrate (COM) as the most common present phase in diseased humans. Within the composition of kidney stones, the most prominent compound is calcium oxalate, which is an increasingly common subject of study in laboratory and clinical trials, in order to better understand the reasons for its occurrence in urolithiasis and the inhibition of this mechanism [6]. The main strategy aimed at inhibiting the formation of kidney stones is based on directing the process of crystallization of calcium oxalate into forms of dihydrate or trihydrate. Studies were conducted in which the focus was primarily placed on the influence of the process parameters such as temperature, system pH and the addition of gallic acid as an additive on the formation of different calcium oxalate hydrates. The research provided more understandable insights into the nucleation mechanism and incorporation of gallic acid under different process conditions to better understand the reasons for the formation of stones. An evaluation of crystal morphology and their chemical composition allows us to understand what type of crystal is formed and what influence the additive has on the size and morphology of these crystals
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