Synthesis of High Sensitive Magnetic Nanoparticles and Application for Inflammation Detection

Magnetic nanoparticles (MNPs) have been widely used as contrast agents for magnetic resonance imaging (MRI), drug delivery, and hyperthermia agents. Among them, MRI is one of the important applications of MNPs because the low... [ view full abstract ]

Magnetic nanoparticles (MNPs) have been widely used as contrast agents for magnetic resonance imaging (MRI), drug delivery, and hyperthermia agents. Among them, MRI is one of the important applications of MNPs because the low sensitivity of MRI can be improved by MNPs. The improvement of T2 relaxivity of MNPs still remains as a critical issue. In this study, we reported an easy and large scale-up synthesis technique for high sensitive MNPs via pH regulation during co-precipitation-based method. A large amount of the aggregated MNPs by regulating pH were successfully coated with silica, in which the number of MNP cores in the silica was simply controlled by pH. As a result, the MNPs could form a nanocluster by decreasing repulsion force for each other when the particle surface charge is almost zero in neutral pH state. We report two types of silica-coated magnetic nanoclusters (SMCs) synthesized at pH2.0 and pH4.5, named as SMC2.0 and SMC4.5, respectively. SMC4.5 provides improved T2 relaxivity (270 mM-1s-1 vs. 155 mM-1s-1 for SMC2.0) due to increased number of cores (18 and 6 for SMC4.5 and SMC2.0, respectively). For in vivo T2*-weighted MRI experiments of inflammation animal model, SMC4.5 provided more specific and high sensitive detection of inflammation following in vivo labeling of the SMC4.5 in macrophages in the sites, showing a possibility of minimum dosage due to higher sensitivity. The nanocluster-type SMCs could be a T2 MRI contrast agent with minimum side-effect disease diagnosis and bio-imaging applications.