Chloride ions assisted synthesis of tunable gold nanorods: Seedless synthesis, characterization and in vitro toxicity studies

Abstract Gold nanorods are interesting due to their capability to absorb light in the near infrared (NIR) wavelength range of 600 nm–1200 nm which is ideal for optical therapeutic imaging. Previous reports in synthesis used cetyltrimethylammonium bromide (CTAB) as capping agent via two-step seed-mediated method done in a laborious manner and major disadvantage is batch to batch variations. To address this issue, we have developed a novel synthetic procedure of synthesizing gold nanorods using cetyltrimethylammonium chloride (CTAC) via seedless, one-step method. The seedless method enables rapid formation of monodisperse gold nanorods with tunable aspect ratios (2–4). Gold nanorods have average lengths in range of 40 nm–55 nm and width of 12 nm–18 nm. Characterization of gold nanorods was done using optical spectroscopy, zeta potential, NTA analysis, FTIR and electron microscopy. Toxicity evaluation of the synthesized CTAC capped gold nanorods was studied on liver carcinoma cell line using MTT assay, Propidium Iodide and Trypan Blue Exclusion assay. The biocompatibility of gold nanorods was evaluated on liver cancer cell line (HepG2) in order to determine their safety using various cytotoxicity assays. We observed a size dependent toxicity of gold nanorods when exposed to liver cancer cells.