Improving the homogeneity of superparamagnetic nanoparticles and a study of their physicochemical properties and applications

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) have enormous potential in biomedical applications, including drug delivery, magnetic hyperthermia treatment (MHT), and contrast enhancement for magnetic resonance imaging (MRI). SPIONs larger than 20 nm are generally synthesized with a multi-core structure held together by an external matrix. This typically yields particles with a very broad size distribution, having a polydispersity index (PdI) of about 0.23. This broad size distribution hinders clinical translation of these particles because of safety and performance variability. While several size fractionation techniques have been employed, including magnetic fractionation, centrifugation, gel chromatography, and vacuum filtration to improve nanoparticle size homogeneity, the particle size distribution remains much higher than gold, silica, and other nanoparticles. Therefore, a novel separation method, diffusive magnetic fractionation (DMF), is introduced to narrow the broad size distribution of SPIONs. The DMF is proven to be scalable, controllable and efficient. Its fractionated SPIONs were used to enhance mass transport through biological barriers by a rotational magnetic field. The mass transport of SPIONs showed a strong size dependency. Furthermore, mathematic models were developed and showed a strong correlation between theoretical and experimental data. Therefore, the models are used to predict the result of the fractionation and to optimize the process efficiency.