Core-shell superparamagnetic nanoparticles with interesting properties as contrast agents for MRI

Abstract

Coreeshell nanoparticles (NPs) formed by superparamagnetic iron oxide NPs (SPIONs) coated with inorganic or organically modified (ORMOSIL) sol gel silica exhibited promising properties as negative contrast agents (CA) for MRI applications. The potentiality of these new coreeshell NPs as negative CA for MRI is demonstrated and quantified. The longitudinal and transverse relaxivities of NPs with three different coating compositions were studied at a 7 T magnetic field: silica (TEOS), (3-aminopropyl) triethoxysilane (APTES) and (3- glycidoxypropyl) methyldiethoxysilane (GPTMS). Clearly, it was found that the coreeshell NPs efficiency as CA was strongly depend on the SPIONs coating. All the three coreeshell NPs studied presented a very small effect on the longitudinal relaxation time but a pronounced one on the transverse relaxation time, leading to a very high transverse longitudinal relaxivities ratio, decisive for their efficiency as negative CA for MRI. The effect of the coreeshell NPs on the MRI contrast enhancement is obtained and quantified in a set of MRI of agar phantoms obtained at 7 T magnetic field and with a imaging gradient field of 1.6 T/m. The coreeshell NPs were tested in Zebra-fish (Danio rerio) animal model. Zebra-fish MRI were obtained with animals injected with the three coreeshell NPs and the contrast enhancement validated.