The localization of conjugate was confirmed both by (A)immunofluorescence staining of frozen tumor tissue sections <i>in vitro</i> and (B)optical tumor imaging <i>in vivo.</i>

<p>(A)Mice bearing HepG2 xenograft was injected i.v. with MetFab-DOX and free DOX, the tumor tissue was removed 24 h later and observed after incubated with goat anti-human Fab and FITC-anti-goat IgG. No obvious signal can be found in the tumor tissues from mice treated with DOX as control, while the green fluorescence was observed in mice treated with MetFab-DOX. (B)Mice bearing HepG2 xenograft was injected i.v. with MetFab-Cy5.5 and observed under small animal imaging system. Mice without injection were as blank and mice with cy5.5 injection as control. The fluorescent signal detected at the tumor site reached the highest fluorescent intensity at 12 h post-injection of MetFab-DOX (left). The fluorescent signal in Cy5.5-treated mice disappeared quickly, and could not be observed at 48 h post-injection. In contrast, the fluorescent signal in the MetFab-Cy5.5 group was still observed in tumor tissue at 48 h post-injection (right).