Gold nanoparticle uptake by human T cells. (A) TEM imaging of gold colloid (diameter = 40-45 nm). (B) Brightfield (upper) and darkfield (lower) images of human T cells demonstrate gold nanoparticle uptake by the increased light scattering seen in the AuNP-T cell group compared to T cells alone. (C) ICP-OES analysis of T cell gold content at 24 h using different nanoparticle loading concentrations. Each point is a composite of data acquired from three different T cell donors. (D) Time course data for T cells from a single donor loaded with different concentrations of gold nanoparticles. Optimal loading occurred after 24 h at a concentration between 0.5 and 1.0 nM.