Gold Nanorods are Selective Cytotoxic Agents

Background: Gold nanorods (GNRs) are very promising agents that have multiple applications in medicine and biology. However, the cytotoxic effects of GNRs have not been fully explored. Objective: Therefore, the main objective of this study was to determine the selective cytotoxic effect of GNRs towards several human tumor cell lines. Methods: To address this issue, three sizes of GNRs (10-nm, 25-nm, and 50-nm) were tested against two human tumor cell lines, namely, human hepatoma HepG2 and human prostate PC3 cancer cells. As GNRs are usually stored in soft tissues inside living bodies, we also tested the effect of GNRs on murine splenocyte viability. To determine if the GNRs displayed selectivity cytotoxicity towards cancer cells, active GNRs with the size showing the least cytotoxicity to splenocytes were then tested against a panel of 11 human tumor cell lines and two human non-tumor cell lines. Results: Our results showed that the most cytotoxic size of GNRs is 10-nm, followed by the 25-nm GNRs, while the 50-nm GNRs did not show a significant effect. In addition, the 25-nm GNRs were the least cytotoxic to splenocytes when tested for 24 and 48 h. These GNRs showed a selective cytotoxic effect to prostate cancer PC3 cells with median inhibitory concentration (IC50) = 8.3 + 0.37 µM, myeloblastic leukemia HL60 cells (IC50 = 19.7 + 0.89 µM), cervical cancer HeLa cells (IC50 = 24.6 + 0.37 µM), renal adenocarcinoma 786.0 cells (IC50 = 27.34 + 0.6 µM), and hepatoma HepG2 cells (IC50 = 27.79 + 0.03 µM) when compared to the effect on the non-tumor human cells; skin fibroblast BJ cell line (IC50 = 40.13 + 0.7 µM) or epithelial breast MCF10A cells (IC50 = 33.2 + 0.89 µM). A high selectivity indices (SI) were observed in GNRs-treated PC3 and HL60 cells with values ranging from 1.69 to 4.83, whereas moderate SIs were observed in GNRs-treated HeLa, 786.0, and HepG2 cells with values ranging from 1.19 to 1.63. Other cells did not show a similar selective effect, including human laryngeal HEp2 cells, colon HCT116, metastatic renal adenocarcinoma ACHN cells, and human breast cancer cells (MCF7, MDA-MB-231, and MDA-MB-468 cells). The effect of GNRs was confirmed using the colony formation assay and the effect was found to be cell cycle specific. Finally, it was shown that laser treatment can potentiate the cytotoxic effect of the 25-nm GNRs. Conclusion: GNRs are selective cytotoxic agents and they have the potential to act as candidate anticancer agents.