The characteristics, biodistribution, magnetic resonance imaging and biodegradability of superparamagnetic core–shell nanoparticles

An efficient contrast agent for magnetic resonance imaging (MRI) is essential to enhance the detection and characterization of lesions within the body. In this study, we described the development of biodegradable nanoparticles with a core–shell structure to formulate superparamagnetic iron oxide (CSNP–SPIO) for MRI. The developed nanoparticles were composed of a hydrophobic PLGA core and a positively-charged glycol chitosan shell. The results obtained by transmission electron microscopy, energy dispersive X-ray analysis, electron energy loss spectroscopy, and X-ray diffraction measurement confirmed that the prepared nanoparticles had a core–shell structure with SPIO in their core area. No aggregation of nanoparticles was observed during storage in water, as a result of the electrostatic repulsion between the positively-charged nanoparticles. The magnetic properties of nanoparticles were examined by a vibrating sample magnetometer and a superconducting quantum interference device; the results showed that the superparamagnetism of SPIO was preserved after the CSNP–SPIO formulation. In tracking their cellular internalization pathway, we found that CSNP–SPIO accumulated in lysosomes. In the biodistribution study, a high level of radioactivity was observed in the liver shortly after administration of the 99mTc-labeled CSNP–SPIO intravenously. Once taken up by the liver cells, the liver turned dark on T2* images. Following cellular internalization, CSNP–SPIO were broken down gradually; therefore, with time increasing, a significant decrease in the darkness of the liver on T2* images was found. The aforementioned results indicate that the developed CSNP–SPIO can serve as an efficient MRI contrast agent and could be degraded after serving their imaging function.