Gold nanoparticle-mediated enhancement of radiotherapy responses in 2D and 3D models

Radiotherapy is commonly used as a treatment in over 50% of cancer patients, where radiation is used to kill cancer cells by inducing DNA damage. However, it presents many disadvantages which can be minimised through the use of radiosensitisers, such as gold nanoparticles. Since 3D cultures better mimic in vivo conditions such as tumour resistance, it is important to investigate the responses of these models to radiation treatment as well as develop methods to investigate gold nanoparticle uptake and distribution within them. In this study I used cell lines representative of epithelial and mesenchymal tumours and developed the methods to assess the radio-sensitising potential of uncoated (AuNP), nuclear-targeted (NLS-AuNP) and mitochondrial-target gold nanoparticles, in both 2D and 3D cell culture models. Cell models were incubated with AuNPs and irradiated with doses ranging from 1.25 to 20 Gy of γ-radiation using a Caesium-137 source. Our results show that both uncoated and mitochondrial-targeted nanoparticles were successfully internalised by cells and produced a significant radiosensitising effect in monolayer cultures, translated by a decrease in colony formation, disruption of the cell cycle and increased number of γ-H2AX foci. Whilst 3D models are significantly more resistant, both nanoparticles successfully produced acute sensitisation, with levels of cell death increasing 24h post-treatment. While prolonged effects were not observed, this acute effect could potentially be enhanced by fractioned dosing, inhibiting damage repair and proliferation. Whilst cellular uptake was not observed for NLS-AuNPs, these nanoparticles still produced an increase in radiation-induced DNA damage and a reduction in the acute viability of osteosarcoma spheroids, which could offer new strategies for treatment of these inherently radio-resistant tumours.