HEK 293T/17 cells were incubated with 510-nm QD-CPP assemblies (QD:CPP ratio 1:50) at QD concentrations of: 250 nM (A), 60 nM (B), 15 nM (C) or with 250 nM QDs without CPP (D); cells were also stained with DAPI. Overlay of phase contrast, QD fluorescence (green), and DAPI fluorescence (blue) show the dose-dependent nature of the QD-CPP delivery. Images also show that QD staining is non-nuclear, punctate fluorescence located in the cytoplasm. Negligible cell-surface associated fluorescence was observed. Arrows indicate regions of QD-CPP internalization at lower concentrations. Scale bar is 10 μm.