Abstract: High-atomic-number nanomaterials have garnered significant attention in the field of tumor radiosensitization due to their ability to enhance localized energy deposition and amplify radiation-induced physicochemical damage upon irradiation. The objective of this study was to establish an efficient radiosensitization system for hepatocellular carcinoma (HCC) radiotherapy. To this end, a hydrothermal method was employed to synthesize HfO2 nanoparticles with a primary size distribution of 50-100 nm, a monoclinic crystal phase, and excellent dispersion. The in vivo behavior, radiosensitization efficacy, and preliminary safety of the test substance were systematically evaluated in a rabbit orthotopic liver cancer model following transarterial infusion. TEM, XRD, and EDS characterization indicated that the obtained HfO2 nanoparticles exhibited regular morphology, high purity, and stable crystalline phases. The results of ICP-MS, CT, and TEM analyses demonstrated that following hepatic arterial administration, HfO2 nanoparticles achieved high enrichment and sustained retention within tumor tissues over time. Accumulation in major organs such as the heart, lungs, and kidneys was minimal, with only the spleen—which is rich in phagocytes—demonstrating notable aggregation. The combination of HfO2 and radiotherapy led to a substantial reduction in tumor volume and weight when compared to radiotherapy alone. Histological and molecular analyses revealed that the treatment resulted in extensive necrosis, a significant decrease in Ki-67 positivity, and elevated levels of γ-H2AX expression and intracellular reactive oxygen species accumulation. This finding suggests that HfO2 nanoparticles augment radiation-induced DNA damage and oxidative stress, thereby potentiating the antitumor effects of radiotherapy. Serum cytokine analysis revealed elevated levels of inflammation-related factors in the combination therapy group, accompanied by a relative reduction in lung metastasis burden. This finding indicates that, in addition to directly amplifying local radiation-induced damage, the combination therapy may elicit a systemic immune response. No significant acute toxicity was observed in hematological assessments, biochemical parameters, or major organ pathology, indicating good tolerability of HfO2 nanoparticles under the study dosage and administration conditions. This work provides experimental evidence covering material preparation, in vivo distribution, radiosensitization effects, and preliminary safety for the further development and translational application of HfO2-based nanoradiosensitizers in hepatocellular carcinoma treatment.

Key words: hafnium dioxide nanoparticles, radiosensitization, orthotopic hepatocellular carcinoma; transarterial infusion, tumor metastasis burden