To examine the targetability of the optimal BsAbs-LsbMDDs to HER2-positive tumor cell lines, the cellular uptake of the DIO-loaded BsAbs-LsbMDDs was examined after incubating the DIO-loaded BsAbs-LsbMDDs at a 0.01:1 molar ratio of BsAbs to mPEG with the HER2-positive cell lines of MCF-7/HER2 and SKBR-3 and the HER2-negative cell line of MCF-7 at 37 °C. The gene discussed is ERBB2; the disease is neoplasm.