In vitro biosynthesis and genotoxicity bioassay of silver nanoparticles using plants

Silver nanoparticles (AgNP-P) from AgNO3 were synthesized by using the broth prepared from the aromatic spath of male inflorescence of screw pine, Pandanus odorifer (Forssk.) Kuntze AgNP-P was then characterized by UV–visible spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Functional groups in the broth were analyzed by Fourier Transform infrared spectroscopy (FTIR). Genotoxicity of AgNP-P was assessed by utilizing our well-established Allium cepa   assay system with biomarkers including the generation reactive oxygen species (ROS: O2·- and H2O2), cell death, mitotic index, micronucleus, mitotic aberrations; and DNA damage by Comet assay. Other chemical forms of silver such as Ag+ ion, colloidal AgCl, and AgNP-S at doses 0–80 mg L−1 were included for comparison with AgNP-P. The results revealed that AgNP-P and AgNP-S exhibited similar biological effects in causing lesser extent of cytotoxicity and greater extent of genotoxicity than that was exhibited by Ag+ ion alone. Among different tested chemical forms of silver, colloidal AgCl was identified to be the least cytotoxic and genotoxic. Cell death and DNA-damage induced by AgNP-P were prevented by Tiron and dimethyl thiourea that scavenge O2·- and H2O2, respectively. The present findings demonstrated the role of ROS in the AgNP-induced cell death and DNA damage.