Preparation of the narrow size distribution USPIO in mesoporous silica for magnetic field guided drug delivery and release

Ultra-small superparamagnetic iron oxides (USPIO) with an average diameter of 2 nm were synthesized in mesoporous silica using the method of co-precipitation of Fe²⁺ and Fe³⁺ ions in aqueous solution directly in the silica nanopores. Two types of the silica material, hexagonal phase MCM-41 and mesoporous silica spheres (MSS), were used. The resulting magnetically modified silica samples show high-quality superparamagnetic properties which persist also at low temperatures near 2 K. Their magnetization saturation in an applied external magnetic field exceeds 15 emu/g. The magnetically modified silica samples were studied with the help of the ferromagnetic resonance (FMR), SQUID-magnetometry, X-ray diffraction (XRD), dynamic light scattering (DLS) and TEM/EDX microscopy. The studies were complemented by confirming the possibility of drug release by the modified silica samples where the standard fluorescent dye was used as an example. The prepared material is suggested to be considered for magnetic field guided drug delivery and release. - Highlights: • Magnetically modified silica material for magnetic field guided drug delivery is suggested. • Ultra-small iron oxides (USPIO) in mesoporous silica MCM-41 and MSS are synthesized. • USPIO@MCM-41 and USPIO@MSS are superparamagnetic even in temperature of 2 K. • Their magnetization saturation in an applied external magnetic field exceeds 15 emu/g. • The average size of the synthesized USPIO is 2 nm