The barnase–barstar adaptor system has been successfully used for the preparation of fluorescent complexes for the imaging of tumor cells overexpressing oncomarker HER2/neu, based on 4D5scFv antibodies and QDs of two types 1) QDs modified by mercaptoacetic acid and 2) QDs covered with a polymeric shell [45, 46]. The gene discussed is ERBB2; the disease is neoplasm.