Synthesis, biocompatibility and cell labeling of l-arginine-functional β-cyclodextrin-modified quantum dot probes

A series of quantum dots (QDs), CdSe, CdSe/CdS and CdSe/ZnSe, coated with l-arginine-modified β-cyclodextrin (β-CD-l-Arg) were prepared in a solution of H2O and hexane by ultrasonic method and characterized using PL, UV–vis, TEM, EDX and FTIR techniques. We observed that β-CD-l-Arg-coated QDs are water-soluble and stable with high colloidal properties in water. Their photophysical properties are similar to those of trioctylphosphine oxide (TOPO)-coated nanocrystals. The quantum yield (QY) of β-CD-l-Arg/CdSe/ZnSe QDs in water is 68%, which is much higher than those of β-CD-l-Arg/CdSe/CdS (26%) and β-CD-l-Arg/CdSe (13%). The in vitro cytotoxicity of these QDs was evaluated in ECV-304, SH-SY5Y and Hela cells and low cytotoxicity was observed. In particular, the β-CD-l-Arg/CdSe/ZnSe QDs presented lower cytotoxicity to these cells (CC50 value is 173 μg/mL in ECV-304 cells for 48 h). This may be due to the presence of the ZnSe and β-CD-l-Arg outlayer, which may improve the biocompatibility of QDs. The QDs were further investigated for biological labeling in ECV-304 cells using confocal laser scanning fluorescence microscopy. We found that these QDs were capable of localing to the cytoplasm of cells. These results demonstrate that the β-CD-l-Arg-coated QDs could be used as a potential photoluminescent nanocrystal probing agent with good biocompatibility.