A general approach for providing nanoparticles water-dispersibility by grinding with poly (ethylene glycol)

By using a facile and versatile physical grinding method, poly (ethylene glycol) (PEG) was coated on oil-soluble Fe3O4 and Fe3O4–CdSe nanoparticles stabilized by various ligands to render them hydrophilicity. The successful coating of PEG was not only identified by Fourier transform infrared spectroscopy and thermogravimetric analysis, but also confirmed by the dispersibility of nanoparticles in aqueous solution against centrifugation. The PEG-coating would not obviously reduce the magnetic and fluorescent properties of Fe3O4 and Fe3O4–CdSe nanoparticles. We also found that the coating efficiency in terms of dispersibility and fluorescence is related to the molecular weight of PEG, from which we proposed that the driving force for coating is the hydrophobic interaction between the methylene groups of PEG and alkyl chain of ligands. Additionally, cytotoxicity evaluation of PEG-stabilized Fe3O4 nanoparticles on renal NRK cells showed that the coated nanoparticles would not increase the early-stage apoptosis of cells, and we found PEG-coated cubic Fe3O4 nanoparticles can be uptaken by adipose derived stem cells. Our results indicated that the grinding approach is facile, efficient and versatile for coating PEG on different nanoparticles, and potentially can be extended to other kinds of surface modification for biomedical applications.