X-ray fluorescence analysis, and HAADF-STEM images of unexposed and SWCNT-exposed cells. Panel a-i: typical μXRF maps of P and Fe of macrophages unexposed (upper line) or exposed (lower line) to 50 μg/ml SWCNT for 24 hours (the color scale is a temperature scale, ranging from blue for low concentrations in the element of interest to red for high concentrations); right: P (green) and Fe (red) correlation images. The size of a pixel is 0.25 μm2 (scale bar: 10 μm). Panel a-ii: X-ray fluorescence spectra integrated exclusively over the scanned cells, normalized to the phosphorus signal. Positions of Kα fluorescence peaks of phosphorus (P), sulfur (S), chlorine (Cl), potassium (K) and iron (Fe) are indicated. The inset represents zoomed areas around the positions of the Kα fluorescence peak of iron together with fits of its contribution (dashed lines). Panel b to f: representative HAADF-STEM images of unexposed cell (Panel b), and low (Panel c) or high (Panels d, e and f) magnification of cells exposed to SWCNT for 24 hours. In Panel f, nuclear membrane is clearly visible, separating cytoplasm (left part of the image) from nucleus (right part of the image). Panel g: quantification of isolated iron nanoparticles in the nucleus and the cytoplasm of cells exposed to SWCNT for 3 hours (open bars) or 24 hours (dark bars). Panel h: quantification of minimum distance between iron nanoparticles observed with SWCNT alone (open circles), SWCNT in vesicles (open triangles) or with nanoparticles in cytoplasm or nucleus (open squares). *: p < 0.0001 between groups. Panel i: higher magnification of Panel h for SWCNT alone and SWCNT in cell vesicles. *: p < 0.001 between groups.