The use of polyethylenimine-modified graphene oxide as a nanocarrier for transferring hydrophobic nanocrystals into water to produce water-dispersible hybrids for use in drug delivery

In order to produce water-dispersible nanocrystals, including upconversion nanoparticles (UCNPs) which are the new generation fluorophores and magnetic nanoparticles (Fe₃O₄), a polyethylenimine-modified graphene oxide (PEI-GO) was used as a nanocarrier of nanocrystals, and PEI-GO-nanocrystal hybrids were prepared by transferring hydrophobic nanocrystals from an organic phase to water. Nanocrystals were anchored onto the hydrophobic plane of PEI-GO, which was confirmed by atomic force microscopy and electron microscopy. Molecular dynamics simulation further showed that hydrophobic interaction between PEI-GO and oleic acid molecules coated on the surface of the nanocrystals was the major driving force in the transfer process. The resulting hybrids had high stability in both water and physiological solutions, and combined the functionalities of the nanocrystals and PEI-GO, such as luminescence, superparamagnetism and drug delivery capability. Through π-π stacking interaction between PEI-GO-UCNP and an aromatic drug, PEI-GO-UCNP was able to load a water-insoluble anticancer drug, doxorubicin (DOX), with a superior loading capacity of 100 wt.%. In addition, PEI-GO-UCNP did not exhibit toxicity on the human endothelial cells and PEI-GO-UCNP-DOX showed a high potency of killing cancer cells in vitro.