Tailoring the Pore Structure of Iron Oxide Core@Stellate Mesoporous Silica Shell Nanocomposites: Effects on MRI and Magnetic Hyperthermia Properties and Applicability to Anti-Cancer Therapies

Abstract

Core-shell nanocomposites made of iron oxide core (IO NPs) coated with mesoporous silica (MS) shells are great promising theranostic agents. While the core is being used as an efficient heating nanoagent under alternating magnetic field (AMF) and near infra-red (NIR) light and as a suitable contrast agent for magnetic resonance imaging (MRI), the MS shell is particularly relevant to ensure colloidal stability in a biological buffer and to transport a variety of therapeutics. However, a main challenge with such inorganic nanostructures is the design of adjustable silica structures especially with tuneable large pore which would be useful for instance for the delivery of large therapeutic biomolecules loading and further sustained release. Further, the effect of tailoring porous silica structure on the magneto or photothermal dissipation still remains poorly investigated. In this work, we address a deep investigation of the growth of stellate mesoporous silica (STMS) shell around IO NPs cores and of its micro/mesoporous features respectively through time-lapse and in situ liquid phase transmission electron microscopy (LPTEM) and detailed nitrogen isotherm adsorptions studies. We found here that the STMS shell features (thickness, pore size, surface area) can be finely tuned by simply controlling the sol-gel reaction time affording a novel range of IO@STMS core@shell NPs. Finally, regarding the responses under alternating magnetic fields and NIR light which are evaluated as function of the silica structure, IO@STMS NPs having tuneable silica shell structure are shown to be efficient as T2-weighed MRI agents and as heating agents for magneto and photo-induced hyperthermia. Further, such IO@STMS are found to display anti-cancer effects in pancreatic cancer cells under magnetic fields (both alternating and rotating).