Cell uptake study results of rGel and TAT-Gel on LS174T cells. The cells were incubated with either TRITC-labeled (A) rGel or (B) TAT-Gel for 3 h at 37°C. After incubation, the cells were washed for three times with 10 mg/mL heparin/PBS solution for stringent wash, counterstained the nuclei with Hoechst 33342, and, after three more wash with PBS, the cell images were taken by a confocal microscope utilizing TRITC (red), Hoechst (blue) channels and merged. (rGel: recombinant gelonin, TAT-Gel: recombinant TAT-gelonin fusion protein)