KEY POINTS
- HeLa cells were incubated for four hours with spherical, unfunctionalized gold nanoparticles at 148 µg/mL, then irradiated with 12.6 MeV protons at 2–6 Gy and approximately 4 Gy/min. Separate experiments evaluated 20- and 50-nm particles.
- Gold nanoparticles showed no measurable basal cytotoxicity during incubation periods up to 24 hours. Uptake increased over time to more than 6,000 particles per cell at 24 hours, predominantly within cytoplasmic vesicles rather than the nucleus.
- Clonogenic survival was significantly lower with nanoparticles at 4, 5, and 6 Gy, while no sensitization was detected at 2 Gy and the difference at 3 Gy was not statistically significant. The relative reduction in survival increased with dose and approached 60% at 6 Gy.
- With 50-nm particles, the sensitization enhancement ratio was 1.53 ± 0.07 in the 2022 campaign and 1.30 ± 0.20 in 2023. The corresponding linear-quadratic α parameter increased from 0.264 to 0.581 Gy⁻¹ in 2022 and from 0.322 to 0.454 Gy⁻¹ in 2023.
- The sensitization enhancement ratio with 20-nm particles was 1.39 ± 0.18, with an α parameter of 0.510 Gy⁻¹. This was compatible with the 50-nm results and provided no evidence of a particle-size effect within the tested range.
- After 4 Gy, nanoparticle-treated cells showed greater γH2AX signal and more RPA-positive cells than irradiation alone, supporting increased double-strand-break accumulation and early DNA end resection.
- Nanoparticles did not increase basal reactive oxygen species, but amplified their production after an added oxidative stimulus. Mechanism remains unresolved, and the use of a single cervical cancer cell line, non-targeted particles, and a two-dimensional culture limits clinical interpretation.
CLINICAL TAKEAWAY
Gold nanoparticles produced reproducible, dose-dependent proton sensitization under controlled laboratory conditions, with no clear difference between 20- and 50-nm particles. This is mechanistic preclinical evidence—not support for clinical use—and requires validation in additional tumour models, three-dimensional cultures, in vivo systems, and clinically relevant nanoparticle-delivery strategies.