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

- Porous Fe3O4@SiO2 NRs shows enhanced MRI contrast agent and drug carrier properties.
- The stable aqueous dispersion of NRs exhibits a high R2 relaxivity of 192 mM−1 s−1.
- The porous NRs also work as a nanocarrier for DOX with a loading efficiency of 65%.
- The drug release study shows a pH-dependent behavior and is higher in acidic pH (4.3).

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 ~520 nm and diameter ~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 ~450 Oe. The aqueous suspension of the NRs is stable over a time frame of one month and exhibits a high R2 relaxivity value of 192 mM−1 s−1. The R2 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 pH-dependent 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 ~58% at pH 4.3 and ~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.

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