Theranostic fluorescent silica encapsulated magnetic nanoassemblies for in vitro MRI imaging and hyperthermia

This article reports the synthesis of manganese ferrite nano-assemblies (MNAs) encapsulated with fluorescent silica shell and demonstrates their applicability for magnetic hyperthermia, optical and T-2 contrast MRI imaging with HeLa cancer cells. The MNAs were encapsulated by a double layer of silica shell through a two-step sol-gel process. The inner silica shell contains rhodamine-B isothiocyanate (RITC) dye, whereas the outer silica layer is without RITC-dye, helps to prevent photo-bleaching and increase photo-luminance. MNAs@Dye-SiO2@SiO2 exhibited a high magnetization of 90.43 emu g(-1) with a remarkably high r(2) value of 598 +/- 2 mM(-1) s(-1) (Mn + Fe). The cellular uptake of MNAs@DyeSiO(2)@SiO2 was observed by the presence of fluorescent red granulated spots in the cytoplasm of HeLa cells, confirming its efficacy for optical imaging. High transverse relaxivities r(2) (darkening effect) were observed in HeLa cells incubated with MNAs@Dye-SiO2@SiO2 in comparison to HeLa cells without particles. An 80-85% cell death was achieved on induction of magnetic hyperthermia with HeLa cells at the lowest Hf factor value (3.3 +/- 109 A m(-1) s(-1)). Our results show MNAs@Dye-SiO2@SiO2 as a novel multifunctional theranostic nanoprobe, which can realize its applicability for diagnostic and real time monitoring the efficacy of ongoing cancer therapy.