Figure 4.

Visualization of the detailed tumor distribution of targeted SPIONs by T2 color mapping and histological analyses. (A) The T2-weighted MR images were subjected to pseudo-color mapping to reveal detailed signal changes in tumor tissues. Remarkable signal reduction can be seen in blue, corresponding to roughly 4/5, 3/4, and 1/4 of tumor area at 6 hr post-contrast with HSP1-, HSP2-, and HSP4-Dex-Fe₃O₄ nanoparticles, respectively. (B) Histological analyses of H460 tumor tissue specimens acquired 24 hrs after injection of HSP1-, HSP2-, HSP4-,or Ctrl P-Dex-Fe₃O₄ nanoparticles. Sections were stained with Prussian blue to detect Fe deposition, and were counterstained with Nuclear Fast Red. Targeting peptides enhanced extravasation of SPIONs out of blood vessels and deep penetration of SPIONs for cancer cell binding, while most control-SPIONs were washed out and thus rarely detected in tumor. Yellow arrows indicate blood vessels of tumor tissue. (C) Quantification of Prussian blue reaction products from the representative tumor sections. **, P<0.01; * * *, P<0.001 compared with Ctrl P-Dex-Fe₃O₄ group.