Daniel Navarro da Rocha

Bioactivity Assessment of Ag-HA

Cell culture medium has been used as an alternative to Kokubo’s solution in order to approach in vitro to in vivo bioactivity assessment. Moreover, the production of biomaterials with silver ions (Ag) has shown an antimicrobial effect and these are potential graft materials to prevent or reduce bacterial infection. In the present study, synthesis of hydroxyapatite (HA) and silverdoped hydroxyapatite (Ag-HA) with 0.13 mol% Ag (mol Ca:Ag) were performed and the bioactivity assessment was analyzed by scanning electron microscopy with field emission gun (FEG-SEM). The Ag-HA samples showed discrete bone-like apatite formation, indicating bioactivity behavior after in vitro incubation in McCoy cell culture medium after 7 days. Silver introduction into hydroxyapatite structure showed to be effective to produce a bioceramic with potential antibacterial effect and bioactivity.

Mg substituted apatite coating from alkali conversion of acidic calcium phosphate.

In this work, two solutions were developed: the first, rich in Ca2+, PO43- ions and the second, rich in Ca2+, PO43- and Mg2+, defined as Mg-modified precursor solution. For each Mg-modified precursor solution, the concentrations of Mg2+ ions were progressively increased by 5%, 10% and 15%wt. The aims of this research were to investigate the influence of magnesium ions substitution in calcium phosphate coatings on titanium surface and to evaluate these coatings by bioactivity assay in McCoy culture medium. The obtained coatings were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis, and the presence of Mg ions was confirmed by the inductively coupled plasma atomic emission spectroscopy (ICP) analysis. In vitro bioactivity assay in McCoy culture medium showed bioactivity after 14days in incubation for the HA and 10% Mg-monetite coatings. The high chemical stability of Mg-HA coatings was verified by the bioactivity assays, and no bone-like apatite deposition, characteristic of bioactivity, was observed for Mg-HA coatings, for the time period used in this study.

Chlorhexidine Adsorption in Hydroxyapatite and Alginate Microspheres by Extrusion in Zinc and Calcium Chloride

In this work, the adsorption of a low-concentration solution of chlorhexidine (CHX), an antimicrobial drug, in hydroxyapatite (HA) and alginate microspheres was studied. The microspheres were formed by extrusion of a 1:10 mixture of alginate and HA in two different divalent solutions: CaCl2 and ZnCl2. UV-Vis spectroscopy showed that the microspheres adsorbed approximately half of the chlorhexidine in solution, which was initially at 0.2%. XRD patterns obtained prior adsorption confirmed the presence of HA as the only crystalline phase. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) analysis were performed before and after CHX adsorption. The spheres produced in CaCl2 solution did not show significant change after adsorption. However, samples obtained in ZnCl2 solution showed a different microstructure, with the presence of crystals with a high Zn concentration. X-Ray Fluorescence (XRF) confirmed the presence of ZnO in the samples after CHX absorption.

Slip Casting Used as a Forming Technique for Hydroxyapatite Processing

Ceramic materials have particular properties when compared to other classes of materials, exhibiting poor ductility as an example. Slip casting is a widely used ceramic forming technique, and already established in the literature and in the ceramic industry. This study aims to present slip casting as a processing route for producing hydroxyapatite (HA) struts, and show the thermal phase stability. The ceramic suspension was produced and stabilized with hydroxyapatite powder, deionized water and polyethylene glycol 400. The slip was poured into gypsum mold. The green bodies were heat treated at 900 and 1100°C. Hydroxyapatite was the only phase present in all samples, before and after heat treatments. Density measurements showed that the densification was higher for the ceramic bodies sintered at 1100°C, when compared to the ones calcined at 900°C.

Characterization of Piezoelectric and Bioactive NaNbO3 from Metallic Niobium and Niobium Oxide

In this study, stoichiomectric sodium niobate was synthesized by two alkali routes. On the first route, niobium oxide was used as precursor, whereas metallic niobium was the precursor used for NaNbO3 synthesis.

Temperature Influence on the Calcium Phosphate Coatings by Chemical Method

The increasing interest in the use of brushite and monetite as resorbable calcium phosphate cements or graft materials is related to the fact of these phases being metastable under physiological environment, with higher solubility than hydroxyapatite phase. In this study, X-ray diffraction (XRD) and scanning electron microscopy with field emission gun (FEG-SEM) analyses were performed in order to assess the temperature influence on the production of calcium phosphate coatings by a chemical deposition method. Titanium substrates were successfully coated with brushite and monetite by a chemical deposition method and a brushite-monetite transformation was assessed with the increasing temperature. Brushite deposition was kinetically favored at low temperatures, whereas monetite was the major phase at higher temperatures.

Synthesis of Ag-Hydroxyapatite

Silver-bioceramics have a great potential to optimize the bone grafts materials to avoid microorganism infections on patients. The present study synthesized and characterized hydroxyapatite doped with silver (Ag), by an acidic route of precipitation method, and the proposal of the Ag-HA synthesis is to promote the bioactivity and bactericidal ability with less toxicity for organism. The samples were analyzed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analysis. There was a pronounced grain growth after 1100°C HA and AgHA heat treatments for both HA and Ag-HA powders, observed by FEG-SEM analysis. XRD patterns of AgHA sintered at 1100°C showed HA as the main phase, but also a secondary whitlockite phase. However, 100% HA was observed for the Ag-HA samples heat treated at 700°C and 900°C. However, pure HA showed decomposition at 900°C. The acidic route of precipitation method showed to be effective for silver-doped hydroxyapatite production.

Bioactivity Assessment of Calcium Phosphate Coatings

Nowadays, bioactive coatings or modifications on titanium surface have been tested in vitro and in vivo. In this study, two types of calcium phosphate coatings were produced by a chemical deposition method and their bioactivity assay in cell culture medium were investigated. The calcium phosphate coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with field emission gun (FEG-SEM) analyses. Titanium substrate was successfully coated with brushite using chemical deposition method and, after a second step of conversion, the hydroxyapatite coating was obtained. The hydroxyapatite coating showed a bioactivity property after 14 days’ incubation in McCoy medium culture.

Apatite Coatings from Ostrich Eggshell and its Bioactivity Assessment

In this work a two-step thermochemical deposition of calcium phosphate from ostrich eggshell on titanium surface was performed. After the deposition, the coatings were immersed into 0,1M KOH solution in order to favoring HA precipitation. The coatings were characterized by scanning electron microscope with field emission gun (FEG-SEM), and X-ray diffraction (XRD) analysis. Bioactivity assessment was performed in cell culture media, McCoy 5A medium, for 14 days. XRD patterns showed brushite/monetite as the phases present at first deposition step; in the second deposition step XRD patterns indicated HA phase peaks on titanium surface. After 14 days on McCoy 5A medium, brushite/monetite coatings revealed bone-like apatite precipitation, showing bioactivity; hydroxyapatite coatings showed a surface modification but no significant bone-like apatite precipitation, thus lower bioactivity. The use of ostrich eggshells as an alternative source to obtain bioactive calcium phosphate coatings showed to be effective.

Adhesion Characterization of Zinc-Substituted Hydroxyapatite Coatings

In this study, hydroxyapatite and Zn-containing hydroxyapatite coatings were produced and characterized with respect to adhesion. The coating technique consists of a two-step hydrothermal process. X-ray diffraction (XRD) analyses showed that, in the first step, the coatings consisted of parascholzite (JCPDS-01-086-2372), a mixture of parascholzite and monetite (JCPDS-01-071-1759), or parascholzite and brushite (JCPDS-72-0713), depending on Zn concentration in the precursor solution. The second step consisted of an alkali conversion in a KOH solution. The final coating was identified as pure hydroxyapatite (HA) or Zn-doped hydroxyapatite, depending on the precursor solution Zn content. Scratch tests on the pure HA coatings showed higher adhesion, when compared to Zn-substituted HA coatings.