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The aim of this study was the synthesis and structural characterization of SiO2–Al2O3 microspheres with SiO2 core and (100 − x)Al2O3·xFe2O3 (x = 0, 5, and 10 mol%) shell. Smooth spherical silica particles of uniform size around 1 μm have been synthesized as core material based on the Stöber method. In order to enhance the specific surface area, the silica particles were coated with a thin nanostructurated shell, about 15 nm, of aluminum and iron oxides (100 − x)Al2O3·xFe2O3 (x = 0, 5, and 10 mol%). The embedding of iron oxide in the covering shell was related to potential applications of these composite biomaterials for contrast enhancement in magnetic resonance imaging (MRI) and at the same time for local treatments of cancer by hyperthermia. The XRD results point out the amorphous structure of the obtained core–shell particles. The TEM images evidence continuous shell coating of silica spherical microparticles and the XPS analysis of the surfaces prove the occurrence of iron oxide on the outermost layer of the microspheres. Both FTIR and XPS results evidence the formation of Al–O–Si linkage proving that Al2O3 and SiO2 are chemically bonded in the investigated core–shell microspheres. Highlights: Amorphous SiO2–Al2O3–Fe2O3 core–shell microspheres of mean diameter under 1.5 μm. Silica core was synthetized using Stöber method. Porous Al2O3–Fe2O3 shell of about 15 nm was nucleated by electrostatic attraction. SiO2–Al2O3–Fe2O3 clay type nanocrystalline layer self-assembled as shell on SiO2 core. Iron ions occur on the outermost layer of the core–shell microspheres. [ABSTRACT FROM AUTHOR]

70SiO 2 ·30Al 2 O 3 and 70SiO 2 ·20Al 2 O 3 ·10Y 2 O 3 aluminosilicate microparticles with potential biomedical applications were investigated with respect to composition effect on structure and bioactivity tested in vitro , as response to simulated body fluid. The local structure of the samples was evaluated by Fourier transform infrared (FT-IR) and magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The results indicate that the addition of yttrium to aluminosilicate microspheres influences the surface properties and induces an enhanced bioactivity. [ABSTRACT FROM AUTHOR]

Abstract: The study aims to characterize surface properties of aluminosilicate microspheres incorporating yttrium, with potential biomedical applications. Micrometric particles of spherical shape were obtained by spray drying method. The behavior of aluminosilicate microspheres without yttrium and with yttrium was investigated under in vitro conditions, by seven days incubation in simulated body fluid (SBF). The surface elemental composition and the atomic environments on outermost layer of the microspheres, prior to and after incubation in SBF were evaluated by X-ray photoelectron spectroscopy (XPS) in order to investigate their bioactivity. The results were analyzed to underline the effect of yttrium addition on surface properties of the aluminosilicate microspheres and implicitly on the behavior of the samples in simulated body environments. [Copyright &y& Elsevier]