Figure 3

Interactions between NDs and Cu ²⁺ determine their internalization fate. a: STXM images of copper distribution in a typical control L929 cell (top left), cell after incubation with NDs (top right), Cu²⁺ (bottom left), and NDs-Cu²⁺ mixture (bottom right) for 24 h. The range of quantities noted by the color bar is from 3.2 × 10⁻⁶ to 7.0 × 10⁻⁶ in (top left), from 3.9 × 10⁻⁶ to 7.2 × 10⁻⁶ in (top right), from 2.4 × 10⁻⁶ to 7.2 × 10⁻⁶ in (bottom left) and from 6.5 × 10⁻⁶ to 5.0 × 10⁻⁵ in (bottom right). The scanning step was 50 nm. b: Imaging of intracellular copper distribution by microXRF. Elemental maps of copper (upper) and zinc (lower) are drawn. The size of a pixel is 3 μm × 3 μm. c: Intracellular Cu²⁺ concentration determined by ICP-MS (**p < 0.01, one-way ANOVA for comparison).