Radiotherapy (RT) is a therapeutic modality that deliver a precise dose of ionizing radiation in a specific tumour volume, promoting the irradiation of tumor cells with as minimal damage as possible in surrounding normal tissues.⁽¹⁾ Besides the evolution of equipment and technology, this therapy still has some problems related with radioresistance, which consequently increase the recurrence at 5 years.^(2,3) Over the years, gold nanoparticles (AuNP) have attracted a lot of interest in cancer therapies due their unique chemical, optical and physical properties.^(4,5)

So, it was synthetized two different types of AuNPs – spherical (AuNP_sp) and rods (AuNP_r) for treat human prostate cancer cell line (PC3) and it was observed cell behavior when treated cells were irradiated with three fractions of 2,5 Gy. AuNPs were characterized using UV-Vis and TEM to confirm their size and shape. After, cells were treated with different concentrations of AuNPs from 0 to 1.0 mM during 24h. The results showed that none of the forms of AuNPs show signals of cytotoxicity until 1.0 mM, with exception of 1mM of AuNP_r, where cells exhibit cytotoxicity around ~10%. Taken all together, AuNP_sp and AuNP_r demonstrated be effective to reduce the cell viability when associated to RT. Comparing both structures, AuNP_r demonstrated a higher dose-dependency with and without radiation and under irradiation the inhibition of cell growth is higher when compared to control (no treatment). These results demonstrate for the first time the possibility of different forms of AuNPs can be used as potential radiosensitizer for prostate cancer cells.