To understand the toxicity of nanoparticles, most scientists have focused on the materials metal cores. But now researchers have shown that the chemicals that decorate silver nanoparticle surfaces can change their toxicity. Known for their antibacterial properties, silver nanoparticles find use in medical devices, textiles, and other products. In 2010, Mitchel Doktycz of Oak Ridge National Laboratory and his colleagues reported that unlike other silver nanoparticles, those with fatty oleate coatings were not toxic to bacteria. Those results, published in the journal Environmental Science & Technology, led Doktycz and his team to wonder whether chemical coatings could make particular nanoparticles more toxic to bacteria but less toxic to eukaryotic cells. The researchers synthesised and purified silver nanoparticles with four different chemical surfaces. They then tested the particles toxicity toward mouse cell lines from the lung and immune system and used microscopy to look for damage to the cells membranes. Nanoparticles coated with an ammonium-containing polymer were the most toxic to cells, followed by those coated with proteins and oleates. Uncoated silver nanoparticles proved the least toxic. Lung epithelial cells were less likely to die or experience membrane damage than macrophages were. The results offer insights that may help materials scientists match nanoparticles and their coatings with applications, says Anil Suresh, first author of the study and now a staff scientist in molecular medicine at City of Hope, a cancer research centre in Duarte, California. Doktycz now wants to understand the details of how cells interact with these nanoparticles and their coatings, including how the cells might modify the surface chemicals.
Chemical & Engineering News, 12 January 2012 ;http://pubs.acs.org/cen/news ;