Toxicity, preparation methods and applications of silver nanoparticles: an update

Nanoparticles (range under 100 nm) prepared by different technology modes including physical, chemical, biological have many applications. Like in the same way silver nanoparticles are used for different beneficial actions like antimicrobial- antibacterial, antifungal and antiviral, anti-inflammatory, anticancer, water treatment, cosmetics, and in the textiles industry. As silver nanoparticles have shown wide application by different mechanisms against various pathophyisiological conditions. To maintain safety under their use, the study of the toxicity of silver nanoparticles has become more important. Health agencies like WHO, NIOSH, EPA, EFSA & EU have issued guidelines for unrisky exposure limit of silver nanopartricles in drinking water, food and breathing. The main purpose of this article is to summarize genotoxicity, cytotoxicity, neurotoxicity, reproductive toxicity of silver nanoparticles in both in vitro and in vivo studies focused on mechanism and methods of detection. The main mechanism of silver nanoparticles toxicity involves disruption of the mitochondrial respiratory chain, which results in the generation of ROS and the stoppage of ATP synthesis which further leads to a cascade of toxic events. ROS production measured by the technique like flow cytometry using DCFHDA dye and other method includes a confocal microscope, lipid peroxidation, etc. Different assay techniques used for evaluation of different kind of toxicities such as the comet assay, MTT assay, and histological assay, are also discussed.