Gold Nanoparticle Complexes with PAMAM Dendrimers for In Vitro Cancer Cytotoxicity Assessment: Synthesis via Ascorbic Acid Reduction

Ascorbic acid plays an important role in the human body due to its antioxidant and anti-inflammatory properties, as well as its involvement in collagen synthesis, enzymatic regulation, and the biosynthesis of corticosteroids and selected neurotransmitters. Owing to these diverse functions, it is used both in the prevention and supportive treatment of several disorders and as a mild, non-toxic reducing agent in the synthesis of gold nanoparticles (AuNPs). In the present study, a method for synthesizing gold nanoparticles was developed using second-generation poly(amidoamine) dendrimers (PAMAM G2) with an ethylenediamine core as stabilizing agents and ascorbic acid as the reducing agent. The synthesis was performed using two techniques: sonication and microwave irradiation. A comparative analysis was conducted for colloidal systems obtained at various molar ratios of PAMAM G2 dendrimers to chloroauric acid (ranging from 1:1 to 1:5). The presence of gold nanoparticles was confirmed using ultraviolet–visible spectroscopy (UV–Vis). Nanoparticle diameters and zeta potentials were determined by dynamic light scattering (DLS). The sizes of the metallic cores were estimated using scanning transmission electron microscopy (STEM). Furthermore, the morphology and topography of entire complexes deposited on silicon substrates were visualized using atomic force microscopy (AFM). For cytotoxicity studies on human breast adenocarcinoma and human osteosarcoma cell lines, the most stable colloids—those obtained at a PAMAM G2:HAuCl4 molar ratio of 1:3—were selected. Results indicate that the synthesized nanoparticles exhibit slightly higher cytotoxicity compared with AuNPs/PAMAM G2 complexes reduced with sodium citrate, as evidenced by lower EC50 values (the concentration responsible for reducing cell viability to 50%). It should be emphasized, however, that AuNPs/PAMAM G2 reduced with ascorbic acid are significantly smaller, with diameters of approximately 10 nm, whereas citrate-reduced nanoparticles exhibit diameters of around 20 nm. These results indicate that nanoparticle size, rather than the chemical nature of the reducing agent, is a dominant factor governing the cytotoxic response of AuNPs/PAMAM G2 complexes.