Encapsulation of magnetic CoFe2O4 in SiO2 nanocomposites using hydroxyapatite as templates: A drug delivery system

Abstract This research focuses on the synthesis of composite CoFe 2 O 4 (CoF) nanoparticles coated with SiO 2 using hydroxyapatite (HAp) as a template (CoFSi) and the pH controlled release of indomethacin (IMC) drug from this nanocomposite. The formation of the CoFe 2 O 4 -HAp (CoFHAp) nanoparticles and of the CoFe 2 O 4 @SiO 2 (CoFSi) nanoparticles were monitored using XRD, FT-IR, that TEM, SEM, and ED studies. The magnetic properties are measured with a VSM. The TEM images showed the CoFe 2 O 4 to have a core–shell structure encapsulated by a silica coating with an average size of 50 nm. BET showed the mean pore sizes of the silica shell to be approximately 10–20 nm and the surface area to be 212.8 m 2  g −1 . Magnetization ( M s ) and remnant ( M r ) magnetic properties of CoFSi nanocomposite decreased upon silica coating (from ∼14 to 2 emu g −1 for M s of CoF and CoFSi, respectively). In contrast, the coercivity ( H c ) of the uncoated CoFe 2 O 4 (317 Oe) is lower than that of the coated nanocomposites (1250 Oe of CoFSi). In vitro drug loading of the CoFSi nanoparticles and its pH-responsive (pH = 4.0 and 7.0) controlled release were investigated using IMC as a model drug. It was seen that the release of the IMC drug was significantly faster at a pH of 4.0 compared to that at a neutral pH 7.0. Furthermore, the lower concentration of ions release (iron and cobalt) from CoFSi was observed after aging for 50 h.