Silica-based microspheres with aluminum-iron oxide shell for diagnosis and cancer treatment

•new mesoporous core-shell microspheres with silica core and 1:1 Al2O3-Fe2O3 shell•shell thickness of alumina or alumina mixed with iron oxide is up to 40 nm•high network connectivity of SiO4 structural units inside the core•on outermost layer of core-shell microspheres Al is preponderantly hexacoordinated•superparamagnetic ferrite is developed in Al2O3-Fe2O3 shell•the microspheres are bioinert and denote a good stability in SBF Monodispersed silica-based microspheres have been prepared by hydrolysis and condensation of tetraethoxysilane (TEOS) in a water–ethanol mixed solution using dodecylamine (DDA) as hydrolysis catalyst and template. Core-shell samples were produced by electrostatic attraction and heterogeneous nucleation of alumina or mixed alumina and iron oxide (1:1) shells on mesoporous silica core microspheres. The iron oxide embedded in the shell structure may be considered both for contrast improvement in magnetic resonance imaging and for the local treatment of cancer by hyperthermia. SEM/TEM analysis proves the spherical shape of the silica particles, the shell development on their surface as well as the distribution of aluminum and iron in the whole shell. The outermost layer of the microspheres was primary investigated by XPS, while the structural characterization of the samples was achieved using XRD, FTIR, EPR and NMR techniques.