The Cytotoxicity of Aqueous Extract and the Biogenic Silver Nanoparticles Derived from the Extract.

Green synthesized silver nanoparticles (AgNPs) have become popular because of their promising biological activities. However, for most of these nanoparticles, the cytotoxic effects have not been determined and their safety is not guaranteed. In a previous study, we successfully synthesized AgNPs (-AgNPs) using an extract of , a medicinal plant traditionally used in South Africa to treat skin conditions. -AgNPs were shown to have significant antimicrobial and wound-healing activities. Fibroblast cells treated with extracts of and -AgNPs demonstrated an enhanced growth rate, which is essential in wound healing. These nanoparticles therefore have promising wound-healing activities. However, the cytotoxicity of these nanoparticles is not known. In this study, the toxic effects of extract and -AgNPs on the non-cancerous skin fibroblast (KMST-6) were determined using in vitro assays to assess oxidative stress and cell death. Both the extract and the -AgNPs did not show any significant cytotoxic effects in these assays. Gene expression analysis was also used to assess the cytotoxic effects of -AgNPs at a molecular level. Of the eighty-four molecular toxicity genes analysed, only eight (, , , , , , , and ) were differentially expressed. These genes are mainly involved in fatty acid and mitochondrial energy metabolism. The results support the finding that -AgNPs have low cytotoxicity at the concentrations tested. The upregulation of genes such as , , and also support previous findings that AgNPs can promote wound healing via cell growth and proliferation. It can therefore be concluded that -AgNPs are not toxic to skin fibroblast cells at the concentration that promotes wound healing. These nanoparticles could possibly be safely used for wound healing.