Compact PEGylated polymer-caged quantum dots with improved stability

Compact PEGylated polymer-caged quantum dots were prepared by covalently cross-linking the surface ligands using bifunctional poly(ethylene glycol). CdSe/ZnSe/ZnS quantum dots prepared in organic solvent via conventional synthesis method were firstly transferred to water phase by surface ligands exchange with glutathione molecules, and then cross-linked by bifunctional PEG through the carboxyl-amine coupling by carbodiimide method. Compared with small molecules capped QDs, polymer-caged QDs using PEG crosslinker have shown improved colloidal and pH stability, lower cell toxicity and non-specific binding, and still maintain compact hydrodynamic diameters (<15 nm) and monodispersity. This surface crosslinking strategy can also be used to improve the stability of other similar nanoparticles.