Porous Fe3O4-SiO2 core-shell nanorods as high-performance MRI contrast agent and drug delivery vehicle

A high-performance MRI contrast agent and a drug nanocarrier have been realized in porous Fe3O4@SiO2 nanorods (NRs). The Fe3O4@SiO2 NRs of length similar to 520 nm and diameter similar to 180 nm are synthesized by annealing FeOOH@SiO2 nanorods at a temperature of 300. under continuous flow of forming gas. The magnetic measurement confirms that the Fe3O4@SiO2 NRs is ferrimagnetic in nature with magnetization of 20 emu/g and coercivity HC similar to 450 Oe. The aqueous suspension of the NRs is stable over a time frame of one month and exhibits a high R-2 relaxivity value of 192 mM(-1) s(-1). The R-2 darkening effect is also observed in HeLa cells incubated with NRs in comparison to untreated control cells. The porous Fe3O4@SiO2 NRs further work as an excellent carrier for doxorubicin (DOX) drug with loading efficiency of 65%. The drug release study shows a pHdependent behavior and is higher in acidic pH (4.3) as compared to the physiological pH (7.4). After 72 h, the cumulative DOX release is found to be similar to 58% at pH 4.3 and similar to 17% at pH 7.4. The induction heating studies of the NRs exhibit a sharp increasing trend of SAR value with the increase of magnetic field.