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