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 (Agmet), 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. LE2Ag1 [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 LE2Ag1 nanocomposite exhibited an LC50 value similar to the effective concentration (EC50) value of Cisplatin and about 3 times larger than Doxorubicin. LE2Ag1 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.