This study examined the interaction of silver nanoparticles (Ag NPs) with human endothelial cells. Transmission electron microscopy and dynamic light scattering were used to characterize the 40nm and 80nm BPEI- and lipoic acid-coated Ag NPs. The nanoparticles were then incubated with human umbilical vein endothelial cells (HUVECs) for 24 hours. Microscopy showed intracellular uptake of Ag NPs in HUVECs and changes to cellular morphology at 10 μg/mL concentrations. Cell viability assays also demonstrated dose-dependent toxicity of Ag NPs to HUVECs regardless of size, surface charge, or chemistry. The results indicate the physicochemical properties of Ag NPs influence their interaction and toxicity in human