Superparamagnetic Iron Oxide Nanorod Carriers for Paclitaxel Delivery in the Treatment and Imaging of Colon Cancer in Mice

A multifunctional magnetic drug delivery system was developed and explored as an efficient and less invasive technique to improve colon cancer diagnosis and therapy in mice. In this system, superparamagnetic iron oxide nanorod cores enhanced passive targeting by bandaging a magnet adjacent to the tumor site, whereas pluronic F127 shell acted as the carrier for paclitaxel. The pluronic-conjugated superparamagnetic iron oxide cores were prepared using the hydrothermal method. It was found that the initial pluronic concentration exerted a significant effect on the distribution of the diameters and lengths of the nanorods. Despite the variation in pluronic concentrations and dimensions of iron oxide products, all the samples exhibited negligible coercivity and remanence, confirming their superparamagnetic characteristics. The pluronic F127-superparamagnetic iron oxide nanocarriers were then prepared by encapsulation of nanorods into pluronic micelles and assessed for paclitaxel loading. Results showed that paclitaxel was incorporated into the core of the micelles through hydrophobic interactions, and that elevating both paclitaxel concentration and temperature increased the loading efficiency. The therapeutic effect of paclitaxel-loaded nanocarriers was then tested in in vitro and in vivo colon cancer models. Compared to docetaxel, the paclitaxel-loaded magnetic nanocarriers significantly suppressed tumor growth and improved survival time of xenograft mice. The accumulated magnetic nanocarriers inside the tumor also served as a contrast agent and enhanced magnetic resonance imaging localization and visualization of the small tumor.