CA9 and breast cancer: We found that PLGA‐PEG‐mAbCAIX NBs easily and specifically enriched at the surface and cytoplasm of MCF‐7 cells in response to tamoxifen treatment compared with the binding rate between NBs and CAIX knockdown cell surface (Figure 3E,F), indicating that CAIX‐targeted nano‐ultrasonographic probe PLGA‐PEG‐mAbCAIX NBs have relative high specificity and enable to detect hypoxic breast cancer cells upon the exposure to tamoxifen in vitro.