Precipitation of calcium oxalates under conditions of hyperoxaluria: the influence of amino acids relevant for pathological biomineralization

U ovom radu provedena su sustavna istraživanja spontanog taloženja kalcijeva oksalata pri tri različite kompleksnosti (jednostavan sustav, NaCl sustav i sustav umjetnog urina) i pri dva početna pH (pHi = 5,0 i pHi = 9,0). U svim sustavima dominantno taloži kalcijev oksalat monohidrat (COM) osim u sustavu umjetnog urina pri pHi = 9,0, ci(C2O42-) ≥ 6,0 mmol dm-3 i ci(Ca2+) ≥ 7,5 mmol dm-3 gdje taloži smjesa COM i kalcijeva oksalata dihidrata (COD). Istraženo je djelovanje sedam aminokiselina (nepolarne - Ala, Phe; polarne - Gly, Ser, Cys i nabijene - His, Asp) na spontano taloženje kalcijeva oksalata u uvjetima hiperoksalurije (ci(Ca2+) = 7,5 mmol dm-3 i ci(C2O42-) = 6,0 mmol dm-3) s ciljem rasvjetljavanja njihove uloge na taloženje hidrata kalcijeva oksalata. U sva tri promatrana sustava zabilježen je značajan utjecaj promatranih aminokiselina na morfologiju i rast kristala COM. Pri pHi = 9,0 uočene promjene su izraženije. Jedino u sustavu umjetnog urina pri pHi = 9,0 evidentirana je promjena sastava; polarne aminokiseline i nepolarna Phe inhibiraju taloženje COM. U ovom radu je po prvi puta sintetiziran COD uz primjenu ultrazvučnog miješanja. Kristalno sjeme COD habitusa u obliku pravilnih tetragonalnih bipiramida s prizmom pripremljeno je u ultrazvučno mješanom sustavu: ci(Ca2+) = 9,00 mmol dm-3, ci(C2O42-) = 2,33 mmol dm-3 i c(citrat) = 9,00 mmol dm-3 (ci(Ca2+)/ci(C2O42-) = 3,86). Zapaženo je da omjer ci(Ca2+)/ ci(C2O42-), c(citrat) i način miješanja značajno utječu na morfologiju COD kristalaIn this Thesis, systematic research of spontaneous precipitation of calcium oxalate at three different complexities (simple, NaCl and artificial urine system) and two initial pH (pHi = 5.0 and 9.0) was conducted. In all investigated systems, dominant precipitation of calcium oxalate monohydrate (COM) was observed, except in artificial urine system at pHi = 9.0, ci(C2O42-) ≥ 6.0 mmol dm-3 and ci(Ca2+) ≥ 7.5 mmol dm-3 where precipitation of a mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) occured. The influence of seven amino acids (nonpolar - Ala, Phe; polar - Gly, Ser, Cys and charged - His, Asp) on spontaneous pecipitation of calcium oxalate in hyperoxaluria conditions (ci(Ca2+) = 7.5 mmol dm-3 and ci(C2O42-) = 6.0 mmol dm-3) was studied in order to elucidate their role in precipitation of calcium oxalate hydrate. In all three investigated systems, significant influence of studied amino acids on morphology and crystal growth of COM was noted. The changes were more pronounced at pHi = 9.0. Only in the artificial urine system at pHi = 9.0, the change in composition was observed, polar aminoacids and nonpolar Phe inhibit precipitation of COM. In this Thesis, COD was synthesized for the first time with ultrasonic mixing. Crystal seed of COD in a shape of proper tetragonal bipramids with prism was prepared in ultrasonically mixed system: ci(Ca2+) = 9.00 mmol dm-3, ci(C2O42-) = 2.33 mmol dm-3 and c(citrate) = 9.00 mmol dm-3 (ci(Ca2+)/ci(C2O42-) = 3.86). It was observed that the ci(Ca2+)/ ci(C2O42-) ratio, c(citrate) and the way of mixing singnificantlly influenced morphology of COD crystals

Electrochemical and UV/VIS Study of L-Histidine and Its Complexes with Cobalt and Nickel

In this work oxido-reduction properties of L-histidine were studied by cyclic and differential pulse voltammetry in a pH range from pH 4–10. The results have shown that L-histidine is not electroactive in a pH range from pH 4 to pH 9, while oxidation peak of L-histidine’s imidazole ring at pH 10 was detected with differential pulse voltammetry. It has been found that the oxidation peak current of L-histidine increased with the increase of its concentration in a solution. Adsorption of oxidation product of L-histidine on a glassy carbon electrode surface was also detected. Voltammetric techniques (cyclic and differential pulse voltammetry) and UV/VIS spectroscopy were used to study formation of L-histidine complexes with transition metals. It has been found that L-histidine formed octahedral complex with metal ion (Co2+ and Ni2+) in a 1 : 1 ratio. This work is licensed under a Creative Commons Attribution 4.0 International License

ELECTROCHEMICAL DETECTION OF VITAMIN C IN REAL SAMPLES

Electrochemical properties of vitamin C (also known as L-ascorbic acid) have been studied by cyclic and differential pulse voltammetry in the model systems in order to develop simple and suitable method for vitamin C detection in real samples. The results indicated that vitamin C oxidation is a quasi-reversible and diffusion-controlled process, as well that the oxidation product of ascorbic acid, dehydroascorbic acid is adsorbed on the glassy carbon electrode surface. Calibration curve was constructed and the linear response was obtained in a concentration range from 0.0025 mol dm-3 to 1.0 mol dm-3. Vitamin C was successfully determined in real samples (fruit juices and food supplement) with cyclic voltammetry within concentration range from 0.034 mol dm-3 to 0.340 mol dm-3. In addition, antioxidant activity of vitamin C in real samples was determined using DPPH assay with a good linear correlation obtained between the cyclic voltammetry results and the results evaluated by DPPH assay of the samples

Green Approach in Synthesis of Bio-Inspired Materials

In this Special Issue, we focus on biomineralization/pathological biomineralization systems and the synthesis of bioinspired materials. This Special Issue promotes the current trend of “green chemistry”, and, as such, in all published papers, only aqueous solutions and eco-friendly additives were used for the production of well-characterized bioinspired materials. This Special Issue contains four papers: three original research papers and one review. Here, a brief introduction of these papers is provided

Mechanochemical synthesis of calcium oxalate

Ova studija prikazuje mehanokemijsku sintezu kalcijeva oksalata u planetarnom kugličnom mlinu, bez i uz prisutnost otapala. Dosadašnja istraživanja su uglavnom bila usmjerena na otopinsku sintezu kalcijeva oksalata. U ovom radu opisujemo drugačiji pristup, koji će donijeti nova saznanja o sintezi kristala kalcijeva oksalata, a koje su uzrokovane utjecajem mehaničke energije. Cilj istraživanja je sinteza, identifikacija i karakterizacija pojedine oksalatne hidratne faze sintetizirane iz kalcijevih soli (klorida, nitrata i sulfata). Ispitivan je utjecaj brzine mljevenja i praćena je reakcija u ovisnosti o vremenu sinteze. Strukturalna i termička svojstva uzoraka ispitana su FTIR spektroskopijom i termogravimetrijskom analizom (TGA). Morfološke karakteristike kalcijeva oksalata te raspodjela veličine čestica određene su optičkom mikroskopijom i dinamičkim raspršenjem svjetlosti (DLS)

Calcium oxalate and gallic acid: structural characterization and process optimization toward obtaining high contents of calcium oxalate monohydrate and dihydrate

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

Precipitation of Calcium Oxalate Monohydrate Under Nearly the Same Initial Supersaturation

Spontaneous precipitation of calcium oxalate monohydrate (COM) in additive-free systems with nearly the same initial supersaturation has been investigated. The influence of thermodynamic parameters such as: temperature (t = 25, 36.5 and 48 °C), calcium concentration range of 5 mmol dm−3 ≤ ci(Ca2+) ≤ 10 mmol dm−3 and pH (5.6, 6.5 and 7.5), on the potential changes in structure, morphology and crystal size of COM have been studied. The values of the initial parameters were varied in a wide range and included values relevant for mimicking the physiological conditions related to those in biological systems and kidney stone formation. The results contributed to the knowledge about the influence of the selected individual parameters as well as their interplay influence on in vitro precipitation of COM. The findings have indicated that COM was the only precipitated phase exhibiting predominant dendritic morphology. The effects on crystal size, structure and morphology are more pronounced at higher temperature, pH and calcium concentration. These results provide basis for future studies of overall mechanism of COM formation and the future studies of kidney stone prevention

Preparation of multifunctional N-doped carbon quantum dots from citrus clementina peel: investigating targeted pharmacological activities and the potential application for Fe3+ sensing

Carbon quantum dots (CQDs) have recently emerged as innovative theranostic nanomaterials, enabling fast and effective diagnosis and treatment. In this study, a facile hydrothermal approach for N- doped biomass-derived CQDs preparation from Citrus clementina peel and amino acids glycine (Gly) and arginine (Arg) has been presented. The gradual increase in the N-dopant (amino acids) nitrogen content increased the quantum yield of synthesized CQDs. The prepared CQDs exhibited good biocompatibility, stability in aqueous, and high ionic strength media, similar optical properties, while differences were observed regarding the structural and chemical diversity, and biological and antioxidant activity. The antiproliferative effect of CQD@Gly against pancreatic cancer cell lines (CFPAC-1) was observed. At the same time, CQD@Arg has demonstrated the highest quantum yield and antioxidant activity by DPPH scavenging radical method of 81.39 ± 0.39% and has been further used for the ion sensing and cellular imaging of cancer cells. The obtained results have demonstrated selective response toward Fe3+ detection, with linear response ranging from 7.0 µmol dm−3 to 50.0 µmol dm−3 with R2 = 0.9931 and limit of detection (LOD) of 4.57 ± 0.27 µmol dm−3. This research could be a good example of sustainable biomass waste utilization with potential for biomedical analysis and ion sensing applications

A scanning electrochemical microscopy characterization of the localized corrosion reactions occurring on nitinol in saline solution after anodic polarization

Sensors and Actuators B: Chemical 321 (2020) 128610. https://doi.org/10.1016/j.snb.2020.12861