Fluorescent Labeling and Size-Dependent Uptake of Mesoporous Silica Nanoparticles in Ovarian Cancer Tumor Spheroids

Ovarian cancer is the most lethal gynecologic malignancy, with most patients presenting at an advanced stage. While surgical debulking improves survival, nonresectable tumors (<1 cm) contribute significantly to morbidity and remain difficult to treat. Nanocarrier-based drug delivery systems offer an innovative approach to targeted therapy and palliation. In vivo models have demonstrated that intraperitoneally delivered mesoporous silica nanoparticles (MSNs) preferentially accumulate in tumors with low systemic exposure, enabling targeted chemo- and radiotherapy. MSNs are particularly suited for radiotherapeutic delivery, as their strong interactions with tumor extracellular matrices drive selective uptake. Additionally, they exhibit excellent stability under neutron flux, allowing for loading with stable isotopes and irradiation immediately prior to administration. High radionuclide retention after dilution further minimizes systemic exposure and toxicity. A key question remains regarding how MSN size influences tumor accumulation. This study investigates the size-dependent accumulation of MSNs on ovarian cancer tumor spheroids. Five MSN sizes were fluorescently labeled and incubated with cultured spheroids. Post-incubation fluorescence was used to quantify nanoparticle retention, and batch yield data were recorded. Findings provide insight into the impact of particle size on tumor targeting, with potential implications for MSN-based drug delivery in cancer treatment.