To test the role of hypoxia‐targeted ultrasonographic NBs‐loaded with the CAIX antibody (PLGA‐PEG‐mAbCAIX) in detection of resistant breast cancer cells treated by tamoxifen, we first conjugated FITC‐biotin with targeted ultrasonographic NBs to be green fluorescent visible under a confocal microscope. The gene discussed is CA9; the disease is breast carcinoma.