Aim and Background: In recent years, there has been a growing emphasis on theranostic nanomedicine. This new strategy combines therapeutic and diagnostic agents in drug delivery systems (DDSs) simultaneously. Superparamagnetic iron oxide nanoparticles (SPIONs) are used as MRI contrast agents that can raise the system\\\\\\\\\\\\\\\'s local temperature by converting magnetic energy into heat. Mesoporous silica nanoparticles (MSNs) have several advantages as DDSs. The gold NPs are suitable gatekeepers to trap the drug molecules inside the pores and can be used in X-ray-based computed tomography (CT) imaging. For targeted drug delivery, we used aptamer-conjugated nanoparticles against EpCAM-positive colorectal cancer (CRC) cells. Methods: In this study, we synthesized SPION-MSNs loaded with oxaliplatin. Moreover, EpCAM aptamer was used for the active targeting of HT-29 colorectal cancer cells. In vitro tests including cellular internalization, MTT assay, and evaluation of the cell death mechanism were performed. In vivo assessments on immunocompromised female C57BL/6 mice confirmed the targeted accumulation of nanoparticles at the tumor site by MRI and CT imaging. Results and discussion: The backbone (SPION-MSN) was fully characterized and TEM images demonstrated a mean diameter of ~20 nm. Compared to EpCAM-negative CHO cells, the targeted nanocarriers exhibited higher levels of cytotoxicity and cellular uptake in HT-29 CRC cells. Quantitative analysis revealed that at 12 h after injection, the MRI and CT signal intensity values of targeted nanocarriers were significantly higher than those of the non-targeted NPs. Conclusion: A targeted nanocarrier platform based on SPION-MSN could be potentially used as “theranostic” nanoparticles with both imaging capabilities and therapeutic function.

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