Background: Improving anti-cancer drug delivery performance can be achieved through designing smart and targeted drug delivery systems (DDSs). For this aim, it is important to evaluate overexpressed biomarkers in the tumor microenvironment (TME) for optimizing DDSs. Materials and methods: Herein, we designed a novel DDS based on magnetic mesoporous silica core–shell nanoparticles (SPION@MSNs) in which release of doxorubicin (DOX) at the physiologic pH was blocked with gold gatekeepers. In this platform, we conjugated heterofunctional polyethylene glycol (PEG) onto the outer surface of nanocarriers to increase their biocompatibility. At the fnal stage, an epithelial cell adhesion molecule (EpCAM) aptamer as an active targeting moiety was covalently attached (Apt-PEG-Au@NPs-DOX) for selective drug delivery to colorectal cancer (CRC) cells. The physicochemical properties of non-targeted and targeted nanocarriers were fully characterized. The anti-cancer activity, cellular internalization, and then the cell death mechanism of prepared nanocarriers were determined and compared in vitro. Finally, tumor inhibitory efects, biodistribution and possible side efects of the nanocarriers were evaluated in immunocompromised C57BL/6 mice bearing human HT-29 tumors. Results: Nanocarriers were successfully synthesized with a mean fnal size diameter of 58.22± 8.54 nm. Higher cytotoxicity and cellular uptake of targeted nanocarriers were shown in the EpCAM-positive HT-29 cells as compared to the EpCAM-negative CHO cells, indicating the efcacy of aptamer as a targeting agent. In vivo results in a humanized mouse model showed that targeted nanocarriers could efectively increase DOX accumulation in the tumor site, inhibit tumor growth, and reduce the adverse side efects. Conclusion: These results suggest that corporation of a magnetic core, gold gatekeeper, PEG and aptamer can strongly improve drug delivery performance and provide a theranostic DDS for efcient CRC therapy.

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