Stability of 65Zn-radiolabeled Qdots with a polymer coating. (A) Dialysis of 65Zn-radiolabeled and polymer-coated Qdots. The Qdots were transferred to a dialysis tube and the dialysis buffer was removed every 24h and tube and buffer were measured. 65Zn appears not to be stably incorporated: there is small release (≈4%/24h) of 65Zn2+ ions. (B) SEC of 65Zn-radiolabeled and polymer-coated Qdots. (C) Desalting of Qdots in a 10 kDa centrifugal filter unit. The radioactivity in the filtrate indicates a slight loss of the radioactive label. The resuspension and filtration of the Qdots was repeated two times. The black line shows the elution profile of the nanoparticles whereas the red line represents the profile of the activity of 65Zn. Nanoparticles and radioactivity are located in the same fraction (24 min), although unbound 65Zn ions can also be found (40 min) directly after filtration.