MB and neoplasm: The tumor uptake of Mb after injection of Mb@Gd-NTs was 7.88 folds higher than that injection of free Mb (4.62 vs. 0.52 %ID/g measured at 24 h and 2 h after injection, respectively) (Fig. 3g), demonstrating enhanced delivery by Mb@Gd-NTs, which was mainly due to the obviously prolonged blood circulation of Mb@Gd-NTs proven by pharmacokinetics studies (Fig. 3h).