Correlation of biocapping agents with cytotoxic effects of silver nanoparticles on human tumor cells†
Metal nanoparticles are used in a wide range of commercial products such as cosmetics, food packaging and household detergents. Owing to interesting antimicrobial properties, silver nanoparticles (Ag NPs) are commonly used in many commercial products. Recently, green approaches using plant extracts at room temperature have been developed for the synthesis of Ag NPs. Here we explored a one-pot approach, which combines capping, reducing agents and templates in one bioextract for synthesizing water soluble Ag NPs. Ginger, coffee and mint extracts were used for the synthesis of water soluble Ag NPs. The as-synthesized nanostructures were characterized using transmission electron microscopy and UV-Vis spectroscopy. The toxicity of Ag NPs with different capping agents was studied using hepatocellular liver carcinoma cells (HepG2) and human cervical cancer cells (HeLa). The level of toxicity was evaluated using changes in cell morphology, cell viability and oxidative stress studies. Ag NPs caused a decrease in the amount of ATP in cells while plant extracts alone did not have significant effect on the amount of ATP. It is interesting to note that bioextract capped Ag NPs do not increase but decrease production of reactive oxygen species (ROS) in a dose dependent manner, which could mostly be attributed to the antioxidant activity of biocapping agents on the surface of nanoparticles. Ag–mint, Ag–ginger and Ag–coffee NPs treatment caused cell cycle arrest in the G2/M phase and Ag–mint NPs exposure resulted in cell cycle arrest in the sub G1 stage. Annexin-V propidium iodide staining showed a large amount of apoptosis in Ag–mint NPs treated cells. A possible mechanism of toxicity of Ag NPs resulted from interruption of ATP synthesis, which further caused DNA damage and cell death through apoptosis. A complete elimination of toxicity, especially at higher concentrations of Ag NPs has not yet been achieved.