Enhanced biocompatibility and biostability of CdTe quantum dots by facile surface-initiated dendritic polymerization

The synthesis of stable, low toxic, multifunctional, and water-soluble quantum dots (QDs) is of crucial importance for nanobiotechnology. An in situ anionic ring-opening polymerization strategy was successfully employed to grow multihydroxyl hyperbranched polyglycerol (HPG) from surfaces of aqueous synthesized QDs directly, affording multifunctional CdTe@HPG nanohybrids. The grafted HPG content can be adjusted from about 25 to 80 wt % by manipulating the feed ratio of glycidol monomer to QDs. The resultant CdTe@HPGs still show strong fluorescence and well water-solubility, and can conjugate functional biomolecules (e.g., amino acids) with their multiple reactive hydroxyls. Cytotoxicity measurements reveal that the CdTe@HPGs are much less toxic than the pristine QDs in human lung cancer cells SPCAI and more grafted HPG leads to less toxicity, due to the envelope of biocompatible HPG on QDs. It was found that the pristine QDs were unstable and their fluorescence decreased greatly or was even completed quenched after 24 h in SPCAI cells, whereas the QD@HPGs still exhibited strong fluorescence. This report opens the door for using in situ controlled/living polymerization to tailor QDs with biocompatible dendritic polymers readily and casts a light for obtaining robust nontoxic functionalized QDs and applying them in vitro and in vivo.