In this study, uptake mechanisms of the anti-mPEG/anti-HER2 BsAb-unbound/bound DTX-loaded LsbMDDs were examined, and their physical characteristics were evaluated, including the particle size and distribution, morphology, optimal BsAbs/mPEG molar ratio, cell viability, in vitro drug release, and biopharmaceutical characteristics of the tumor proliferation inhibition, pharmacokinetics (PK), and biodistribution. The gene discussed is ERBB2; the disease is neoplasm.