Time-of-addition experiment. HeLa-CD4-LTR-β-gal cells were infected with HIV- 1IIIB, and silver nanoparticles (1 mg/mL) and different antiretrovirals were added at different times post infection. Activity of silver nanoparticles was compared with (A) Fusion inhibitors (Tak-779, 2 μM), (B) RT inhibitors (AZT, 20 μM), (C) Protease inhibitors (Indinavir, 0.25 μM), and (D) Integrase inhibitors (118-D-24, 100 μM). Dashed lines indicate the moment when the activity of the silver nanoparticles and the antiretroviral differ. The assay was performed in triplicate; the data points represent the mean and the colored lines are nonlinear regression curves done with SigmaPlot 10.0 software.