| Abstract | Kalcijevi fosfati, teško topljive soli fosfatne kiseline, privlače pažnju kao jedna od glavnih komponenti mokraćnih kamenaca i kostiju. Spadaju u skupinu bioaktivne keramike i stoga su široko rasprostranjeni u medicinskoj industriji kao protetičke prevlake i bioimplantati. Kalcijevi ortofosfati javljaju se u 13 danas poznatih faza. Kalcijev hidrogenfosfat dihidrat (DCPD), poznat kao mineral brušit, jedan je od najvažnijih i najčešćih kalcijevih fosfata. Jedan je od glavnih sastojaka mokraćnih kamenaca, zajedno s kalcijevim oksalatima, mokraćnom kiselinom i njenim solima, a koristi se i za koštane implantate. TiO2 nanočestice javljaju se u tri polimorfna oblika: rutil, anatas i brukit. U svakodnevnici se primjenjuju u obliku aerosola, suspenzija ili emulzija, najviše u preparatima za kožu i zaštitu od Sunca te zubnoj pasti, ali i u hrani. TiO2 nanočestice posjeduju izvrsna mehanička svojstva kao što je visoki modul elastičnosti, stoga privlače pažnju kao aditivi za poboljšavanje mehaničkih svojstva kalcijevih fosfata. Cilj ovog rada bio je odrediti utjecaj TiO2 nanočestica na proces taloženja DCPD-a. Kalcijev hidrogenfosfat dihidrat pripremljen je miješanjem jednakih volumena otopina kalcijeva klorida i natrijeva dihidrogen fosfata. Istražena su tri taložna sustava: sustav A (c(CaCl2) = c(Na2HPO4) = 0,032 mol dm^–3, c(NaCl) = 0,3 mol dm^-3), sustav B (c(CaCl2) = c(Na2HPO4) = 0,032 mol dm^–3 + c(TiO2) = 10 ppm, c(NaCl) = 0,3 mol dm^-3) te sustav C (c(CaCl2) = c(Na2HPO4) = 0,032 mol dm^–3 + c(TiO2) = 50 ppm, c(NaCl) = 0,3 mol dm^-3) uz magnetsko miješanje i pri početnom pH 5,5 pri kojem je DCPD stabilna faza. Na temelju dobivenih pH krivulja određena su indukcijska vremena. Nastali talog analiziran je FTIR spektroskopijom, rendgenskom difrakcijom na polikristalnom materijalu (PXRD) a morfologija je analizirana na svjetlosnom mikroskopu. TiO2 nanočestice analizirane su FTIR spektroskopijom, PXRD-om i pretražnom elektronskom mikroskopijom (SEM). Potenciometrijske krivulje pokazale su podjednako ubrzanje taloženja kalcijevog hidrogenfosfata dihidrata u prisutnosti TiO2 nanočestica koncentracija 10 i 50 ppm. FTIR i PXRD analiza pokazala je da dodatak TiO2 nanočestica u taložni sustav ne utječe na sastav taloga, u svim sustavima nastaju kristali DCPD. Na svjetlosnim mikrografijama je vidljivo da je morfologija kristala DCPD ostala karakterističnog trapeznog oblika, ali je zamućenje bilo jače izraženo u prisutnosti nanočestica. |
| Abstract (english) | Calcium phosphates, the sparingly soluble salts of phosphoric acid, have attracted attention as one of the major components of kidney stones and bones. They belong to the group of bioactive ceramics and are therefore widely used in the medical industry as prosthetic coatings and bioimplants. Calcium orthophosphates occur in 13 known phases. Calcium hydrogen phosphate dihydrate (DCPD), known as the mineral brushite, is one of the most important and common calcium phosphates. It is one of the main ingredients of kidney stones, along with calcium oxalates, uric acid and its salts. It is also used for bone implants. TiO2 nanoparticles occur in three polymorphic forms: rutile, anatase, and brookite. In everyday life, they can be found in the form of aerosols, suspensions or emulsions, mostly in skin and sun protection products and toothpaste, but also in food. TiO2 nanoparticles have excellent mechanical properties such as a high elastic modulus, so they are considered as a possible additive for improving calcium phosphates’ mechanical properties. The aim of this study was to determine the influence of TiO2 nanoparticles on the DCPD precipitation process. Calcium hydrogen phosphate dihydrate was prepared by mixing equal volumes of calcium chloride and sodium dihydrogen phosphate solutions. Three sedimentation systems were monitored potentiometrically: system A (c(CaCl2) = c(Na2HPO4) = 0.032 mol dm^–3, c(NaCl) = 0.3 mol dm^-3), system B (c(CaCl2) = c(Na2HPO4) = 0.032 mol dm^–3 + c(TiO2) = 10 ppm, c(NaCl) = 0.3 mol dm^-3) and system C (c(CaCl2) = c(Na2HPO4) = 0.032 mol dm^–3 + c(TiO2) = 50 ppm, c(NaCl) = 0.3 mol dm^-3) with magnetic stirring at initial pH = 5.5, at which DCPD is a stable phase. Based on the obtained pH curves, the induction time was determined. Further precipitate analysis was performed by FTIR spectroscopy, powder X-ray diffraction (PXRD) and light microscopy. TiO2 nanoparticles were analysed with FTIR spectroscopy, PXRD and scanning electron microscopy (SEM). Potentiometric curves showed equal acceleration of calcium hydrogen phosphate dihydrate precipitation by adding TiO2 nanoparticles in concentrations of 10 and 50 ppm. FTIR and PXRD analysis showed that the addition of TiO2 nanoparticles to the precipitation system does not affect the composition of the formed precipitate, as in all systems DCPD crystals were formed. The light micrographs showed that the morphology of the crystals remained a characteristic trapezoidal shape, but the but the turbidity was more pronounced in the presence of nanoparticles. |
