Figure 4.

a) MR imaging results. U87MG tumor bearing mice were intravenously injected with RGD-Fe₅C₂, RGD-Fe₃O₄, or Fe₅C₂ nanoparticles (10 mg Fe/kg). Scans were performed before, and 4 and 24 h after the administration. In both the RGD-Fe₅C₂ and RGD-Fe₃O₄ groups, black areas (in the RGD-Fe₅C₂ group highlighted by red arrows) were found distributed in the tumors (circled by yellow dotted lines). RGD-Fe₅C₂ induced more significant signal drop than RGD-Fe₃O₄ at both time points. b) Left column: Prussian blue staining with tumor tissues. Positive staining was found in the RGD-Fe₅C₂ group but not in the Fe₅C₂ group. Scale bars, 50 μm. Right column: Prussian blue and integrin β₃ double staining with the tumor tissues. Good overlap was observed in the RGD-Fe₅C₂ group, indicating that the tumor accumulation was mainly caused by RGD-integrin interactions. Scale bars, 10 μm. c) Prussian blue staining with tissue samples from the liver, spleen, lung, kidneys, and brain. Particles were accumulated in the liver and spleen but not in the other major organs. Scale bars, 10 μm.