Controlling Iron Oxide Nanoparticle Clustering Using Dual Solvent Exchange Coating Method.

Superparamagnetic iron oxide nanoparticles (SPIOs) have considerable promise for magnetic resonance imaging, drug/gene delivery, and hyperthermia applications. It has been shown recently that self-assembly of SPIOs into large superstructures can have a significant impact on their magnetic properties and functionality. In this work, we developed a novel method for controlling the clustering of SPIOs with two different core sizes (8 nm and 15 nm) by varying the amount of amphiphilic coating molecules used during the dual solvent exchange coating process. We show that hydrodynamic size and T2 relaxivity can be increased using this approach, while the specific absorption rate is decreased. These results demonstrate a new, simple method for triggering the self-assembly of SPIO clusters using commercially available and biocompatible phospholipid-poly(ethylene glycol) conjugates.