Surface and composition effects on the biphasic cytotoxicity of nanocomposites synthesized using leaf extracts

The Malus sylvestris L. (LE1), Pinus sylvestris L. (LE2), and Sorbus aucuparia L. (LE3) leaves` extracts were used for the synthesis of silver (Ag) nanocomposites containing different amounts of silver chloride (AgCl), silver metal (Ag_met), and silver phosphate (Ag₃PO₄). These nanocomposites were capped with the organic functional groups in the leaf extract. Notably, the nanocomposites caused biphasic cytotoxic response on cells; first attributed to the inhibition of cell growth and second to cell death. The nanocomposites were biocompatible with normal embryonic kidney (HEK293) cells in the cytotoxic range for cancer cells. [25(±1) °C synthesis] nanocomposites exhibited the highest cytotoxicity towards HeLa (lethal concentration- LC₅₀ value of 11.4 μg mL^-1) and A549 (LC₅₀ value of 14.7 μg mL^-1) after 24-h incubation and its efficiency was shown also for the more resistant MCF-7 and MDA-MB-231, however, their respective LC₅₀ values were larger. For the HeLa cell line, this designed nanocomposite exhibited an LC₅₀ value similar to the effective concentration (EC₅₀) value of Cisplatin and about 3 times larger than Doxorubicin. nanocomposite contained Ag₃PO₄ in the composite and P on the surface, higher AgCl content, smaller crystallite size of all nanoparticle phases, and carbon-rich oxygen-deficient surface compared to all other nanocomposites.