Fig. 7

PS-NPs are associated with the marginal zone monocytes/macrophages, identified by Iba-1 staining. Immunohistochemical staining for the spleen macrophages, stained with anti-Iba-1 antibody (a red), and carboxylated PS-NPs (b green) 4 days after a single intravenous injection of nanoparticles. Merged image (c) shows that residual nanoparticles (green) are co-localized with Iba-positivity of marginal zone macrophages (red). Scale bars 250 µm. Confocal images of spleen sections from non-treated (d) or PS-PEG-injected (e, f) mice. Samples were collected 5 min (e) or 4 days (f) after exposure to PS- PEG, and were stained for Iba-1. The sample from non-treated animal (d) serves also as staining control. Enlarged areas of the boxed regions in e and f, show the presence of PS-PEG NPs in Iba-1 positive phagocytotic cells. g The spectra of ROIs indicated the presence of PS-PEG NPs on images of both, 5-min and 4-day samples. The spectrum of each ROI is marked with the same color as it is delineated in the microscopic image. Fluorescence spectra of ROIs were compared against spectrum of tissue autofluorescence (red curves as negative controls) and particle fluorescence (green curves as positive controls). Scale bars 20 µm