ERBB2 and neoplasm: X-ray and X-ray/fluorescence images (Fig. 6a) have shown that TGNs displayed significantly higher tumor accumulation in the BT474 breast cancer xenograft mouse, while no fluorescence signal could be observed in MDA-MB-231 xenograft mice, demonstrating that TGNs would specifically locate and target the HER2-positive breast cancer in vivo.