Ultrasmall Confined Iron Oxide Nanoparticle MSNs as a pH‐Responsive Theranostic Platform

A unique mesoporous silica nanoparticles (MSNs)‐based theranostic platform with ultrasmall iron oxide nanoparticles (NPs) confined within mesopore network has been developed by a facile but efficient physical‐vapor‐infiltration (PVI) method. The highly dispersed Fe species within mesopore channels can synchronously function as the non‐toxic contrast agents for highly efficient T₁‐weighted MR imaging, and as anchoring sites for anti‐cancer drug molecule loading and pH‐responsive release based on the special metal‐ligand coordination bonding between the Fe species and drug molecules. Moreover, the obtained Fe‐MSNs exhibit favorable biocompatibility, enhanced chemotherapeutic efficacy and concurrently diminished side effects due to the non‐specific attack of chemotherapeutic drugs, as well as the capability in circumventing the multidrug resistance (MDR) of cancer cells and suppressing the metastasis of tumor cells in vitro and in vivo. This pH‐resoponsive theranostic agent provides a new promising MSNs‐based anti‐cancer nanomedicine for future biomedical application.