Nano-Size Effect of Hyperbranched Polyglycerol-Grafted Fe₃O₄Nanoparticles

Hyperbranched polyglycerol-grafted Fe3O4 nanoparticles (HPG-grafted MNPs) are newly developed MRI contrast agents with good stability, dispersibility, and biocompatibility. Their magnetic, cell uptake properties may be changed when their size varies. In this study, HPG-grafted MNPs with their size ranging from 8 to 10, 13, and 15 nm were successfully synthesized via a facile one-pot reaction using ferric oxalate pentahydrate as the precursor. With the increase of particle size, HPG-grafted MNPs show increasing trends in saturation magnetization, transverse relaxivities (R2), R2/R1 ratio, and cell uptake. MTT assays indicated that nanoparticles with defferent sizes did not possess significant cytotoxicity toward mouse macrophages and 3T3 fibroblasts. Furthermore, in vivo MRI experiments were carried out with the 8-nm HPG-grafted MNPs injected into a live rabbit. Our results demonstrate that the size of HPG-grafted MNPs, which can be synthetically controlled, played an important role in tuning their magnetic and cell uptake properties. This allows HPG-grafted MNPs exhibit optional and designable properties for their application as an efficient MRI contrast agent.