Flow cytometry analysis of nanoparticle-associated cells revealed less interaction between HER2 positive tumor cells and Herceptin® (monoclonal antibody towards human epidermal growth factor receptor 2 (HER2) protein) conjugated nanoparticles 26, contrary to in vitro results, despite their higher retention in tumors when compared against their plain unconjugated counterpart. Here, ERBB2 is linked to neoplasm.