Immunohistochemical staining of organotypic spinal cord co-cultured with peripheral nerve graft. Co-cultures were incubated for one week with 100 μg/ml green fluorescent MNPs and were stained with anti-pan-neuronal neurofilament to visualize neurons, shown in images (A) and (B). Neurons do not display co-localization with green fluorescent MNPs. Microglia in (C) and (D) were visualized with the microglial marker anti-CD11b/c and demonstrated high amount of MNPs localized in vesicles. Astroglial cells in (E) and (F) were stained with anti-GFAP antibody and showed moderate MNP co localization (arrows). Bars in (A) and (E) represent 75 μm, in (C) 50 μm and in (B), (D) and (F) 25 μm.