Single Nanoparticle in a Silica Shell for Localized Cell Delivery and Radiotherapy

Cerium oxide nanoparticles (CeO 2 NPs) show promise as radiosensitizers due to their capacity for selective enhancement of radiation damage in cancer cells. To advance their application, we developed a modular platform based on monodisperse CeO 2 NPs (≤9 nm), synthesized via a high-temperature organic-phase approach. We subsequently introduced a robust siloxane shell using a reverse microemulsion technique, achieving superior colloidal stability in aqueous media while preserving intrinsic radiosensitizing activity. This surface engineering enables facile covalent conjugation; we exemplify this by functionalizing the NPs with the fluorescent tracer fluorescein isothiocyanate (FITC). This strategy facilitated high-resolution fluorescence microscopy tracking of the intracellular CeO 2 NP distribution without altering the NPs’ physicochemical or radiobiological performance. Comprehensive MTT assays and gene expression analysis confirmed that the functionalized CeO 2 NPs maintained their selective radiosensitization efficacy. This work establishes a robust synthetic and surface engineering strategy for creating traceable, biocompatible CeO 2 -based nanoradiosensitizers, significantly advancing their potential in image-guided cancer therapies.