(A) Tumor-bearing mice were treated with the nanosystem for 3 weeks, and at the end of the treatment, FAM-labeled peptide-NWs (green) were intravenously injected (5mg iron/kg) and allowed to circulate for 5 hours. The mice were further injected with 100μg of DyLight 488 labeled Lycopersicon esculentum lectin, (green). After 5 minutes, the mice were perfused with PBS through the left ventricle of the heart, followed by 4% formaldehyde in PBS. Tumors and organs were collected and processed for fluorescence microscopy. (B) Quantification of NW accumulation in tumors. Slides were scanned using Scanscope. NW fluorescence in 10 random areas of each tumor section (n = 3/group) was quantified using ImageJ software. (****P < 0.0001, paired t test, n = 3 mice per group. Error bars = mean ±SD).