7Efficacy of surface-functionalized Mg1-xCoxFe2O4 (0 ≤ x ≤ 1; Δx=0.1) for hyperthermia and in vivo MR imaging as a contrast agent

Surface-functionalized Mg1-xCoxFe2O4 (0 <= x <= 1; Delta x = 0.1) can be an exciting candidate as an MRI contrast agent and for thermotherapeutic applications. The figure-of-merit, T-2, relaxivity, r(2), of MRI and specific loss power, SLP, of hyperthermia depend on the structural and magnetic properties of the nanoparticles. We synthesized cobalt-substituted magnesium ferrite Mg1-xCoxFe2O4 (0 <= x <= 1 with Delta x = 0.1) nanoparticles using a chemical co-precipitation method. The lattice parameter and average crystallite size increase with the increase in cobalt content. The force-constant of FTIR of the tetrahedral sites increases, and that of the octahedral sites decreases with an increase in cobalt content. The room temperature Mossbauer spectra of Mg1-xCoxFe2O4 show that the Mossbauer absorption area of the A site decreases, and the Mossbauer absorption area of the B site increases with x. The Mossbauer spectra and M-H hysteresis loops at room temperature confirmed that a transition from fast relaxation (superparamagnetic) to mixed slow/fast (superparamagnetic/ferrimagnetic) relaxation occurs with changing cobalt content. The cobalt ion tends to occupy the octahedral B site, which makes the A-B interaction stronger; therefore, we see the above transition. Cytotoxicity experiments on HeLa cells revealed that both chitosan and chitosan-coated magnesium cobalt ferrite nanoparticles are biocompatible. In the Mg1-xCoxFe2O4 series, both r(2) and SLP increase with x because of the increase in magnetization and anisotropy.

Automated summary

Surface-functionalized Mg1-xCoxFe2O4 nanoparticles were synthesized and their structural and magnetic properties were studied for their potential use as MRI contrast agents and for thermotherapeutic applications. The results showed that the lattice parameter, crystallite size, and force constants of the nanoparticles changed with the cobalt content. The Mossbauer spectra and M-H hysteresis loops confirmed the transition in magnetic relaxation behavior with changing cobalt content. Cytotoxicity experiments also demonstrated the biocompatibility of the nanoparticles. Both r(2) and SLP increased with cobalt content in the Mg1-xCoxFe2O4 series due to the increased magnetization and anisotropy.