Toxicological studies on silver nanoparticles: challenges and opportunities in assessment, monitoring and imaging

Abstract

Silver nanoparticles (Ag NPs) are becoming increasingly prevalent in consumer products as antibacterial agents. The increased use of Ag NP-enhanced products may lead to an increase in toxic levels of environmental silver, but regulatory control over the use or disposal of such products is lagging due to insufficient assessment on the toxicology of Ag NPs and their rate of release into the environment. In this article we discuss recent research on the transport, activity and fate of Ag NPs at the cellular and organismic level, in conjunction with traditional and recently established methods of nanoparticle characterization. We include several proposed mechanisms of cytotoxicity based on such studies, as well as new opportunities for investigating the uptake and fate of Ag NPs in living systems.

When enough is enough

“…The antibacterial properties of nanosilver are exploited in a very diverse set of products and applications including dietary supplements, personal care products, powdered colours, textile, paper, kitchenware and food storage. " And like many previous reviews and reports 3,10,14,[18][19][20][21]25,26 , the new report is likely to cite the Consumer Product Inventory maintained by the Project on Emerging Nanotechnologies 27 .…”

“…Two of the review articles in journals were also funded by the European Commission 14,16 . And 2011 saw the publication of five more review articles on nanosilver in scientific journals [21][22][23][24][25] , plus a 136-page report from the Danish Environmental Protection Agency (Danish EPA) about nanosilver and six other nanomaterials 26 .…”

“…Hence, we predict that the SCENIHR's upcoming review will consist of five main sections summarizing: the properties and uses of nanosilver; human and environmental toxicity; microbial resistance; risk assessment; and research needs 3,8,10,14,16,[18][19][20][24][25][26] . We also predict that the SCENIHR's report will say something along the following lines: "Nanosilver is reportedly one of the most widely used nanomaterials in consumer products today but the scale of production and use is unknown.…”

“…Moreover, because inhibition of nitrifying bacteria by nanosilver has been observed in the very few original studies that have been published, the SCENIHR will have to consider this topic under the heading of 'Other environmental, health and safety (EHS) issues' because this phenomenon might affect the proper functioning of wastewater treatment plants 20,23,26 . It remains uncertain whether nanosilver is more toxic than ionic silver, the report is likely to say, because the effects seen in many cases can be ascribed to ionic silver: however, some studies have documented a more pronounced effect associated with nanosilver, but the data is inconclusive 2,9,19,22,24,25 .…”

“…Because there have been very few original studies of the relationship between nanosilver and the development of antimicrobial resistance (less than five to the best of our knowledge), it is likely that the SCENIHR will rely heavily on the seven review articles that have addressed this topic 3,7,10,15,17,19,25 . Evidence that the increasing use of nanosilver may be leading to bacterial and fungal resistance towards silver include reports of resistance to silver-based burn dressings (originally published in the mid-1970s and reviewed Many of these reviews and reports go through the same literature, cover the same ground and identify many of the same data gaps and research needs.…”