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.

In this work, thermo-responsive graphene oxide-perylene bisimides-containing poly(N-isopropylacrylamide) hybrid (TGO) was successfully prepared via non-covalent π-π stacking interactions of GO and perylene bisimides-containing poly(N-isopropylacrylamide) (PBI-PNIPAM). PBI-PNIPAM was synthesized by atom transfer radical polymerization of N-isopropylacrylamide, using bifunctional N,N'-bis[6-(2-chloropropionamide)hexyl] perylene-3,4,9,10-tetracarboxylic acid bisimide (PBI-Cl) as the initiator. The obtained polymer was then characterized by (1)H NMR and fluorescence spectroscopy. The surface chemical states, morphology, and composition of TGO were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), respectively. This new hybrid showed reversible temperature-dependent self-assembly and disassembly at 35.9°C in water. Therefore, it may have great potentials as a convenient adsorbent for removing organic pigment, as exemplified as for removing methylene blue from water with excellent adsorption capacity of 568 mg/g, high removal efficiency of 99.5%, and facile temperature-controlled post-separation of the adsorbent.

Fe3O4 nanoparticles with surface hydroxyl groups (MNP-OH), prepared by the thermal decomposition of ferric oxalate pentahydrate in triethylene glycol, were grafted in situ with polyglycerol through the ring-opening polymerization of glycidol. By this method, hyperbranched polyglycerol-grafted Fe3O4 nanoparticles (HPG-grafted MNPs) can be obtained on an ultra-large scale of 50 g in a single reaction under laboratory conditions, and it is anticipated that the production of the HPG-grafted MNPs could be scaled up with the use of larger reaction vessels. The successful grafting of HPG onto the nanoparticles was confirmed by 1H NMR and XPS analyses. The as-synthesized nanoparticles can be tuned from 8 to 24 nm in diameter by varying the reaction conditions. The size, morphology, and surface component of the nanoparticles were characterized by TEM, XPS, and XRD. The HPG-grafted MNPs are highly dispersible in aqueous media such as cell culture medium and serum. Since these magnetic nanoparticles possess desirable magnetic properties, controllable size, and can be produced by a facile inexpensive method, they can be potentially applied as a novel contrast agent for enhancing a MRI signal.