Fig. 1

Biodistribution of poly(lactic acid) nanoparticles (PLA-NPs) in mucosae and thymus. Representative confocal images of gills (A), thymus (B), skin (C), intestines (D,E), and the olfactory mucosa (F), of wild-type adults immersed for 24 h in 0.01% red fluorescent nanoparticles (NPs). Images were acquired in 40-μm-thick whole-body cryosections, stained with phalloidin (green) and DAPI (blue). (A) In gills, NPs are found in pavement cells lining the branchial cavity (arrowheads), accumulated in cells located in the sub-epithelial compartment (stars), and detected in the blood (arrow). (B) NPs are located in pavement cells lining the branchial cavity above the thymus (arrowheads) and accumulated in cells of the lympho-reticular parenchyma in the thymus (stars). (C) In skin, NPs are visible in keratinocytes (arrowhead), goblet cells (characterized by kidney-shaped nucleus, arrow) and accumulated in intra-epithelial cells (star). (D,E) In the intestine, a high number of NPs is found inside the intestinal lumen (D). As illustrated in the end-gut (D), NPs are taken up by enterocytes (arrowheads), which display a diffuse signal. A number of NPs is also observed in sub-epithelial cells (stars). In the post-midgut (E), NPs are mainly found in apical areas of specialized enterocytes (arrowheads); a subset is also found at the basal epithelial side (arrows). (F) In the nasal mucosa, NP-positive cells are found in the olfactory epithelium (arrowhead) and the lamina (arrows). NPs are accumulated in large cells of the lamina (stars). B, blood vessels; pL, primary lamellae; sL, secondary lamellae; Bc, branchial cavity; Rc, rodlet cells; E, epidermis; D, dermis; Ext, external environment; Lu, Lumen; Ep, epithelium; Lp, lamina propria; Sm, smooth muscles; Lrp, lympho-reticular parenchyma; La, lamina. Scale bar: 10 μm (B,E), 20 μm (A,C,F), and 30 μm (D).