Magnetic characterization of surface-coated magnetic nanoparticles for biomedical application

The influence of the oleic acid surface coating on Fe3O4 and NiFe2O4 nanoparticles on their magnetic and calorimetric characterization was investigated. Fe3O4 nanoparticles (particle sizes of 15-20 and 20-30 nm) and NiFe2O4 nanoparticles (particle sizes of 20-30 nm) were dispersed in oleic acid. The surface coating resulted in a decrease in the dipole-dipole interaction between the particles, which in turn affected the coercivity and heat dissipation of the nanoparticles. The coercivity of the oleic-acid-coated nanoparticles was found to be lower than that of the uncoated nanoparticles. The temperature rise in the oleic-acid-coated nanoparticles was greater than that of the uncoated nanoparticles; this temperature rise was associated with the relaxation losses. The viscosity dependence on the self-heating temperature of Fe3O4 nanoparticles (15-20 and 20-30 nm) under an ac magnetic field was measured. The temperature rise for both the Fe3O4 nanoparticles (15-20 and 20-30 nm) exhibited a strong dependence on viscosity at each magnetic field frequency, and the contribution of Brownian relaxation loss to the temperature rise was revealed. Moreover, an in vitro cytotoxicity test of Fe3O4 and NiFe2O4 was performed using human cervical carcinoma cells (HeLa), and the cytotoxicity of NiFe2O4 nanoparticles was compared to that of Fe3O4 nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.