Purpose

Intracellular localization of gold nanoparticles has been shown to enhance the effects of radiation. However, few studies have investigated the effect of subcellular localization of these particles on enhancing the radiosensitization effect in cells treated with radiation of varying energies and linear energy transfer (LET) levels. Herein, we evaluate the radiosensitization potential of nuclear-targeted gold nanoparticles across a spectrum of energies and LETs.

Methods

Gold nanospheres (AuNSs) were functionalized with a nuclear localization sequence (NLS) peptide to enhance the nuclear accumulation of these particles. Internalization of the particles into the cells was achieved using a cell penetrating peptide (CPP). Cellular and nuclear internalization were assessed in Panc-1 human pancreatic adenocarcinoma cancer cells using western blot (WB), transmission electron microscopy, dark field microscopy and inductively-coupled plasma mass spectrometry (ICP-MS). DNA damage due to radiation was evaluated through γH2AX and 53BP1 foci staining. Clonogenic cell survival assay was performed to evaluate the radiosensitization effect after irradiation with 250-kVp X-rays, Cs-137, Co-60, 6 MV and 100 MeV protons (LET 2.5 and 7.7 keV/µm).

Results

Nuclear-targeted particles (nAuNS) and non-targeted particles (PEGylated, pAuNS) demonstrated similar cellular internalization. However, enhanced uptake of nuclear-targeted particles was observed in the nucleus when compared to non-targeted particles. This was confirmed using dark field microscopy, WB and ICP-MS analysis. DNA double strand breaks through γH2AX and 53BP1 foci staining revealed significantly higher numbers of foci at early (1 hour) and late (24 hour) time points following radiation and nAuNS compared to radiation and pAuNS treatment. Clonogenic cell survival assay revealed significantly higher radiosensitization enhancement factor (REF) at 10% survival fraction for nAuNS compared to pAuNS for all beams assessed. Protons with higher LETs resulted in greater clonogenic cell death and nAuNS further increased radiosensitization whereas pAuNS did not.

Conclusion

Our data demonstrates that, across a spectrum of radiation energies and LETs, nuclear-targeted gold nanoparticles enhance radiosensitization beyond that achievable with strictly intracytoplasmic gold nanoparticles.

Citation Format: Sunil Krishnan, Maureen Aliru. Nuclear-targeted gold nanoparticles as radiosensitizers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3212.