Synthesis and Magnetic Characterization of Maghemite Nanoparticles Designed for Targeted Cancer Therapy

Adopting the procedure described by Hyeon et al [1], oleic acid coated maghemite nanoparticles of 7 nm average size as determined by TEM were synthesized for use in targeted cancer therapy. Here we report their magnetic properties. Using a PPMS magnetometer, magnetization (M) vs. temperature (2 K - 350 K) and magnetic field (up to $\pm$ 90 kOe) was measured under the zero-field-cooled (ZFC) and field-cooled (FC) conditions. The results for H $=$ 100 Oe show a blocking temperature $T_{B} =35K$ which shifts to lower temperatures with increase in H. For$T > T_{B}$, isotherms of M vs. H were measured at several temperatures and, following the procedures reported recently [2], data were fitted to a modified Langevin function: $M=M_{0} L(\mu_{p} H/k_{B} T)+\chi_{a} H$ with $\mu_{p} \simeq 7500\mu _{B} $ per particle. Using this magnitude of $\mu_{p} $, particle diameter D $=$ 6.9 nm is determined which agrees with the TEM data. Procedures for \textit{in vitro} studies include coating with biocompatible polymer and functionalization with therapeutic and targeting ligands. Toxicity testing and determination of \textit{in vivo} activity are in progress.\\[4pt] [1] T. Hyeon et al, J. Am. Chem. Soc. 123, 12798 (2001)\\[0pt] [2] M. S. Seehra et al, J. Phys. Chem. Solids 71, 1362 (2010)