Green synthesis and biological activities of silver nanoparticles prepared by Carpesium cernuum extract

The extract of Carpesium cernuum whole plant was successfully used as a green factory for the synthesis of silver nanoparticles in a one-step, one-pot process. The extract efficiently reduced silver ions to spherical silver nanoparticles. The size was measured as 13.0 +/- 0.2 nm from high resolution transmission electron microscopic images. The reaction yield was determined to be 99.6% using inductively coupled plasma optical emission spectroscopy. The silver nanoparticles were highly stable for 28 days at ambient temperature without forming agglomeration or aggregation of nanoparticles. Dose-dependent antioxidant activity of the silver nanoparticles was observed in terms of the scavenging activity of 2,2-diphenyl-1-picrylhydrazyl radicals. The silver nanoparticles also exerted cytotoxicity on Mus musculus skin melanoma cells (B16F10) and human lung cancer cells (A549) in a dose-dependent manner. Specifically, the cytotoxicity of the silver nanoparticles on A549 cells was closely associated with apoptotic cell death. Cellular uptake of the silver was evaluated via inductively coupled plasma mass spectrometry, and a higher percentage of silver was taken up by A549 cells (22.6%) than by B16F10 cells (17.3%). This result indicated that higher cellular uptake of silver nanoparticles resulted in higher cytotoxicity on A549 cells. Therefore, plant extracts are capable of being valuable natural sources for the green synthesis of silver nanoparticles that exhibit potent biological activities for pharmaceutical and biomedical applications in future nanomedicine.