Actively Targeted Deep Tissue Imaging and Photothermal‐Chemo Therapy of Breast Cancer by Antibody‐Functionalized Drug‐Loaded X‐Ray‐Responsive Bismuth Sulfide@Mesoporous Silica Core–Shell Nanoparticles

Abstract A theranostic platform combining synergistic therapy and real‐time imaging attracts enormous attention but still faces great challenges, such as tedious modifications and lack of efficient accumulation in tumor. Here, a novel type of theranostic agent, bismuth sulfide@mesoporous silica (Bi 2 S 3 @mPS) core‐shell nanoparticles (NPs), for targeted image‐guided therapy of human epidermal growth factor receptor‐2 (HER‐2) positive breast cancer is developed. To generate such NPs, polyvinylpyrrolidone decorated rod‐like Bi 2 S 3 NPs are chemically encapsulated with a mesoporous silica (mPS) layer and loaded with an anticancer drug, doxorubicin. The resultant NPs are then chemically conjugated with trastuzumab (Tam, a monoclonal antibody targeting HER‐2 overexpressed breast cancer cells) to form Tam‐Bi 2 S 3 @mPS NPs. By in vitro and in vivo studies, it is demonstrated that the Tam‐Bi 2 S 3 @mPS bear multiple desired features for cancer theranostics, including good biocompatibility and drug loading ability as well as precise and active tumor targeting and accumulation (with a bismuth content in tumor being ≈16 times that of nontargeted group). They can simultaneously serve both as an excellent contrast enhancement probe (due to the presence of strong X‐ray‐attenuating bismuth element) for computed tomography deep tissue tumor imaging and as a therapeutic agent to destruct tumors and prevent metastasis by synergistic photothermal‐chemo therapy.