Facile Synthesis of Ultrasmall, Highly Stable, and Biocompatible Gold Nanoparticles Stabilized with Lipoic Acid: Cytotoxicity and Structural Characterization

— Using the colloidal method, and lipoic acid as a stabilizer, ultrasmall gold nanoparticles with an average size of 2.5 nm were synthesized. They are highly stable, have COOH functional groups, at concentrations lower than 100 μg/mL are non-cytotoxic, and the synthesis route is simple and economical. UV–Vis, FT-IR, Raman, and TEM spectroscopy were used to analyze their stability, composition and morphology. Furthermore, the cytotoxicity of the gold nanoparticles was evaluated by MTT assay.