Choline Carboxylic Acid Ionic Liquid-Stabilized Anisotropic Gold Nanoparticles for Photothermal Therapy

Gold nanoparticles (AuNPs) are commonly used in cancer research due to their unique physical and optical properties. However, current AuNP synthesis methods often involve cytotoxic cationic surfactants such as cetyltrimethylammonium bromide (CTAB). Tedious CTAB replacement methodologies have been used to increase the biocompatibility, further increasing the complexity of synthesizing biocompatible AuNPs and limiting their biomedical applications. To address this issue, we explore cholinium decanoate (CADA) ionic liquid (IL) as a biocompatible stabilizing agent by replacing CTAB using a simple modified seeded method for synthesizing anisotropic AuNPs for photothermal therapy of triple-negative breast cancer cells (MDA-MB-231). The prepared CADA AuNPs showed a quasi-spherical morphology, confirmed by transmission electron microscopy (TEM) and a broad plasmonic absorption band using vis-NIR spectroscopy. CADA AuNPs exhibited excellent in vitro biocompatibility with both MCF-10A (healthy human mammary cells) and MDA-MB-231 cells. We evaluate their in vitro photothermal efficacy against MDA-MB-231 cancer cells, demonstrating significant cell death even at low AuNP concentration (20 μg/mL), low laser power density (0.6 W/cm², 808 nm continuous laser), and short irradiation time of 5 min, primarily through apoptosis. Overall, this work represents the first effort in using a modified seeded method for synthesizing biocompatible IL-based anisotropic AuNPs for photothermal therapy, offering a promising avenue for future cancer treatment research using ILs.