The dissolution and biological effects of silver nanoparticles in biological media

Abstract

Silver ions and silver nanoparticles have a well-known biological effect that typically occurs in biological or environmental media of complex composition. Silver nanoparticles release silver ions if oxidizing species like molecular oxygen or hydrogen peroxide are present. The presence of glucose as a model for reducing sugars has only a small effect on the dissolution rate. In the presence of chloride ions, precipitation of silver chloride nanoparticles occurs. At physiological salt concentrations, no precipitation of silver phosphate occurs as the precipitation of silver chloride always occurs first. If the surface of a silver nanoparticle is passivated by cysteine, the dissolution is quantitatively inhibited. Upon immersion of silver nanoparticles in pure water for 8 months, leading to about 50% dissolution, no change in the surface was observed by transmission electron microscopy. A model for the dissolution was derived from immersion and dissolution experiments in different media and from high-resolution transmission electron microscopy. A literature survey on the available data on the dissolution of silver nanoparticles showed that only qualitative trends can be identified as the nature of the nanoparticles and of the immersion medium are practically never comparable. The dissolution effects were confirmed by cell culture experiments (human mesenchymal stem cells and neutrophil granulocytes) where silver nanoparticles that were stored under argon had a clearly lower cytotoxicity than those stored under air.They also led to a less formation of reactive oxygen species (ROS). This underscores that silver ions are the toxic species.

Antibacterial activity of silver nanoparticles: A surface science insight

“…This absence of activity in anaerobic conditions has been then backed by other works (Fig. 1C) [33,49,53]. As tests to assess nanoparticles activity are commonly performed on aerobically grown bacteria, it can be speculated that most of the observed results are indeed attributable to ions originating form the nanoparticles dissolution rather than to a direct action of pristine nanoparticles.…”

A systematic review of evidence for silver nanoparticle-induced mitochondrial toxicity

“…59 ROS-induced toxicity of AgNPs due to dissolution has also been seen in vitro. 60 Thus, dissolution of AgNPs is likely to cause mitochondrial toxicity due to silver ion-induced bactericidal mechanisms that are phylogenetically and physiologically conserved between bacteria and mitochondria. An important logistical consideration related to silver ion toxicity is the effect of AgNP sample storage conditions.…”

The concentration-dependent behaviour of nanoparticles

“…mobility, fugacity, non-transient (sink) or transient source) of nanoparticles (NPs) in environmental and toxicological media have been investigated for over a decade, typically at high NP concentrations (e.g. milligram per litre range) which are not relevant to the environment, [1] resulting in some potentially misleading assumptions that (i) NP behaviour is dominated by aggregation and thus their fate is dominated by sedimentation and removal from the water column, or, in porous media, deposition and removal from the aqueous phase [2] ; (ii) NP dissolution is limited for many NPs and rarely are all NPs dissolved fully in environmental and biological media over relevant timescales [1] and (iii) many NPs therefore impart little or no toxic risk to pelagic organisms as a result of limited NP dissolution and NP removal by aggregation and sedimentation. [3] Several NP groups (e.g.…”