Fig. 3

Distribution of Au-4-COONa and Au-3-PEG NPs in the in vitro placental barrier model after 24 h. Co-cultures were exposed to 19.2 μg/mL Au from Au-4-COONa (a–d) and Au-3-PEG (e–h) NPs for 24 h under static conditions. A co-culture without NP treatment was used as negative control. H&E staining of 5 µm thick sections of the co-culture enables allocation of Au signals (a, e, i; adjacent sections to those for LA-ICP-MS). Elemental distribution of ⁷⁹Br to visualize cell structure (b, f, j). ¹⁹⁷Au was measured to localize Au (c, g, k). Overlay of ⁷⁹Br and ¹⁹⁷Au to co-localize Au signals in cells (d, h, l). Elemental distribution map of ⁷⁹Br and ¹⁹⁷Au is represented in signal intensities and Au concentrations (black: minimum, red: maximum), respectively. Images were obtained from one independent experiment