M13-RGD8 uptake in HeLa 229 cells is significantly higher than for WT M13 phage. (A) Quantitated titers of internalized M13-RGD8 (RGD modification on pVIII protein of M13 phage) in HeLa cells compared with wild type (WT, unmodified M13 phage) show that the recovered M13-RGD8 was viable and able to infect the bacterial host cells (E. Coli) up to day 2 and then decreased dramatically after that time to day 10 (pfu, plaque forming unit; *, p<0.0001). (B) Uptake is significantly higher in M13-RGD8 infected cells and peaks at day 1 compared with WT M13 phage. Blue, DAPI; Green, M13-RGD8; 40x; inset, 100x. Data represent three independent experiments.