Fig. 3

a In vivo fluorescence imaging of three representative cell-penetrating peptides (CPPs) and phosphate-buffered saline are displayed by tumor cell line 3 h after the injection of 300 μg of CPPs into nude mice. The tumor mass (red arrow) demonstrated that CPP2 had high selectivity for colorectal cancer cells. R8 and TAT were employed here as representative non-selectively permeable CPP. Green on black and rainbow were the two different capture modes. In the rainbow mode, signal intensity here also meant fluorescence intensity, which was reflected by diverse colors: red > orange > yellow > green > blue (pictured at right). b The tumor mass and organs were excised 3 h after the intraperitoneal injection of the CPPs. The heart, liver, and spleen are arranged in the first row, the lungs, kidneys, and tumor mass are shown in the second row, and a part of the small intestine is shown in the last row. Fluorescence imaging of a variety of organs further verified the in vivo imaging results