Infulence of diferent amino acids on spontanouse precipitation of calcium phosphates

Međudjelovanje malih organskih molekula i/ili makromolekula s anorganskim kristalima važno je za razumijevanje procesa taloženja u prirodi. Između različitih biominerala, kalcijevi fosfati privlače posebnu pažnju zbog uloge u biološkoj i patološkoj mineralizaciji i industrijskim procesima. U novije vrijeme, istraživanja utjecaja aditiva na nastajanje kalcijevih fosfata uglavnom su usmjerena na proteine. Iako su opći principi tih međudjelovanja poznati, uloga pojedinih aminokiselina nije još do kraja razjašnjena. Cilj ovoga rada je istraživanje utjecaja aminokiselina koje pri fiziološkim uvjetima imaju bočne ogranke različitih naboja: fenilalanina (nenabijen), asparaginske kiseline (negativno nabijen), asparagina (polaran, nenabijen), serina (polaran, nenabijen) i lizina (pozitivno nabijen). Napredovanje taloženja kalcijevih fosfata praćeno je potenciometrijski, što je omogućilo određivanje vremena indukcije. Nastali talog analiziran je infracrvenom spektroskopijom s Fourierovom transformacijom, pretražnom elektronskom mikroskopijom, transmisijskom elektronskom mikroskopijom i difrakcijom rendgenskih zraka na praškastom uzorku. Dobiveni rezultati ukazali su da utjecaj aminokiselina na svojstva kalcijevih fosfata ovisi o naboju njihovog bočnog ogranka.Mechanisms of interaction between soluble small organic molecules and/or macromolecules with inorganic crystals are of major importance for crystallization processes in nature. Among different biogenic crystals, calcium phosphates attract attention due to their role in the normal and pathological mineralization, as well as in industrial processes. Recent investigations of the influence of additives on the formation of calcium phosphates are mostly focused on protein and their building blocks, amino acids. Althought general principles of these interactions are known, the role of specific amino acids is still unclear. The aim of this research was to investigate the influence of amino acids with side chains of different properties at physiological conditions: phenylalanine (uncharged, hydrophobic), aspartic acid (negatively charged), arginine (uncharged, polar), serine (uncharged, polar) and lysine (positively charged). The progress of precipitation was followed potentiometrically, which enabled determination of induction time. Fourier transform infrared spectroscopy, powder x - ray diffraction, scanning and transmission electron microscopy were used for characterization of the precipitates. Given results show the influence of amino acids on properties of calcium phosphates. The obtain resultes show that the infuence of amino acids on calcium phosphates’ properties dependes on the charge of their side chain

Influence of Biomacromolecules on Calcium Phosphate Formation on TiO2 Nanomaterials

Calcium phosphates (CaP) composites with biomacromolecules and/or nanomaterials have recently emerged as a potential solution to improve the poor mechanical properties and biological response of CaP. Among the methods available for preparation of such composites, precipitation at low temperatures attracts special interest as it allows preservation of the activity of biomacromolecules. However, precipitation of CaP in the presence of two additives is a complex process that needs to be studied in detail to rationalize composite preparation. This study aimed to investigate co- precipitation of CaP on different TiO2 nanomaterials (TiNMs), including nanoparticles (TiNPs), nanoplates (TiNPls), nanotubes (TiNTs), and nanowires (TiNWs), in the presence of bovine serum albumin (BSA) and chitosan (Chi). The obtained results have shown that both BSA and Chi inhibited transformation of amorphous to crystalline CaP, even in the presence of TiNMs at concentrations that promoted transformation. Chi proved to be a stronger inhibitor due to its more flexible structure. The presence of BSA and Chi did not influence the composition of the CaP formed as calcium-deficient hydroxyapatite (CaDHA) was formed in all the systems. However, both macromolecules influenced the morphology of the formed CaDHA in different ways depending on the type of TiNM used. BSA and Chi adsorbed on all the TiNMs, as confirmed by zeta potential measurements, but this adsorption reduced the amount of CaP formed on TiNMs only in the case of TiNWs. The obtained results contribute to the understanding of the influence of BSA and Chi on CaP precipitation in the presence of nanomaterials and thus to the rational design of CaP-based multi-composite materials

The Fine-Tuned Release of Antioxidant from Superparamagnetic Nanocarriers under the Combination of Stationary and Alternating Magnetic Fields

Superparamagnetic magnetite nanoparticles (MNPs) with excellent biocompatibility and negligible toxicity were prepared by solvothermal method and stabilized by widely used and biocompatible polymer poly(ethylene glycol) PEG-4000 Da. The unique properties of the synthesized MNPs enable them to host the unstable and water-insoluble quercetin as well as deliver and localize quercetin directly to the desired site. The chemical and physical properties were validated by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE–SEM), atomic force microscopy (AFM), superconducting quantum interference device (SQUID) magnetometer, FTIR spectroscopy and dynamic light scattering (DLS). The kinetics of in vitro quercetin release from MNPs followed by UV/VIS spectroscopy was controlled by employing combined stationary and alternating magnetic fields. The obtained results have shown an increased response of quercetin from superparamagnetic MNPs under a lower stationary magnetic field and s higher frequency of alternating magnetic field. The achieved findings suggested that we designed promising targeted quercetin delivery with fine-tuning drug release from magnetic MNPs

OSL study of ion-substituted hydroxyapatites

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a calcium orthophosphate which due to its similarity to mineral part of hard tissue is best known as biomaterial hard tissue regeneration [1]. However, HA has also been among the most studied dosimetric materials in the high dose and retrospective dosimetry, by the EPR (electron paramagnetic resonance) spectroscopy. As HA substituted with different ions is the one occurring in biological systems, ion-substituted HA are increasingly attracting attention as hard tissue biomaterials [2, 3]. But they could as well be used as OSL (optically stimulated luminescence) dosimeters [4]. To test this hypothesis, in this study influence of Mg and Si substitutions on the OSL response of irradiated HA was determined. Mg and Si substituted HA were synthetized by hydrothermal method. Obtained ion-substituted HAs were characterised by powder X-ray diffraction and scanning electron microscopy. EPR spectroscopy were used to follow and control the changes in relation with substituted ions and correlated with pure HA. Obtained results indicate that Mg and Si ion substituted HA can be potential dose indicator material using OSL technique. However, more detailed study of the influence of the ion substitute concentration and type is needed to confirm their applicability as OSL dosimeters.VIII International Conference on Radiation in Various Fields of Research : RAD 2020 : book of abstracts; Virtual Conferenc

Effects of saline solution and simulated body fluid on ion substituted hydroxyapatites EPR spectra

Hydroxyapatite (HA, Ca10(PO4)6(OH)2), a calcium orthophosphate, due to its similarity to the inorganic part of human’s hard tissue, is among the most frequently used hard tissue regeneration biomaterial [1]. As such, the effects of HA ageing in media similar to blood plasma need to be studied, specifically after sterilization with γ-radiation, to better understand the possible structural changes it would undergo in the human body. Moreover, such changes in ion substituted HAs are particularly interesting since so called biological HA is in fact non-stoichiometric poorly crystalline, calcium deficient, Na-, Mg- and carbonate substituted HA (Dorozhkin, 2012) [2]. In this study, HA and 3 different substituted HAs were irradiated to 25 kGy with Co-60 γ-rays and their electron paramagnetic (EPR) spectra were recorded 1, 14 and 28 days after treatment with saline solution and simulated body fluid (SBF) [3]. The ion substituted HAs were doped with Mg and Si: 2% Mg; 2% Mg + 0.4% Si and 2% Mg + 1.25% Si. EPR spectra were analysed, and the most pronounced peaks assigned. The effects of ageing in the two media are presented and discussed.IX International Conference on Radiation in Various Fields of Research : RAD 2021 : book of abstracts; June 14-18, 2021; Herceg Novi, Montenegr

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)

Amorphous Calcium Phosphate Formation and Aggregation Process Revealed by Light Scattering Techniques

Amorphous calcium phosphate (ACP) attracts attention as a precursor of crystalline calcium phosphates (CaPs) formation in vitro and in vivo as well as due to its excellent biological properties. Its formation can be considered to be an aggregation process. Although aggregation of ACP is of interest for both gaining a fundamental understanding of biominerals formation and in the synthesis of novel materials, it has still not been investigated in detail. In this work, the ACP aggregation was followed by two widely applied techniques suitable for following nanoparticles aggregation in general: dynamic light scattering (DLS) and laser diffraction (LD). In addition, the ACP formation was followed by potentiometric measurements and formed precipitates were characterized by Fourier transform infrared spectroscopy (FTIR), powder X- ray diffraction (PXRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results showed that aggregation of ACP particles is a process which from the earliest stages simultaneously takes place at wide length scales, from nanometers to micrometers, leading to a highly polydisperse precipitation system, with polydispersity and vol. % of larger aggregates increasing with concentration. Obtained results provide insight into developing a way of regulating ACP and consequently CaP formation by controlling aggregation on the scale of interest