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Relaxivities of hydrogen protons in aqueous solutions of gold-coated manganese ferrite nanoparticles

Manganese ferrite nanoparticles were synthesized using the reverse micelle method and were coated with gold. TEM (transmission electron microscope) pictures showed that the shapes of the synthesized nanoparticles were almost spherical with an average diameter of 12 nm and a standard error of 4 nm. The bonding status of gold on the nanoparticle surfaces was checked using a Fourier transform infrared spectrometer (FTIR). The T1 and the T2 relaxation times of the hydrogen protons in aqueous solutions of the coated manganese-ferrite nanoparticles were determined using magnetic resonance imaging (MRI). The 1/T1 and the 1/T2 versus concentration curves for the nanoparticles showed a linear dependence. The T1 and the T2 relaxivities were found to be r1 = 6.01 ± 0.12 and r2 = 83.3 ± 0.55 mM−1s−1. The ratio of r2/r1 was 13.9; this is larger than the ratios of r2/r1 for commercial T2 MRI contrast agents, indicating that the nanoparticles studied herein can serve as a T2 contrast agent with high efficacy.