Impact of storage conditions and storage time on silver nanoparticles' physicochemical properties and implications for their biological effects

Abstract

It is increasingly recognized that nanoparticles (NPs) can 'age' while stored, and that the impact of this may lead to divergent results in terms of the observed toxicity of nominally the same NPs. The main goal of this study was to investigate whether (and to what extent) changes in silver (Ag) NPs' properties occur over time and whether storage of the dispersions under different conditions impacts their stability and ageing mechanism, as a function of the NPs' surface capping/charge. We found that both storage time/ conditions and surface chemistry of AgNPs influenced the evolution of the NP properties over time, and that the resulting changes in the NPs' physicochemical properties influenced their toxicity. Observed changes in Ag NPs' toxicity were related to different processes such as NP agglomeration, dissolution, oxidation, capping agent degradation as well attachment of Ag + ions to container walls. Thus, NP 'aging' effects as described here can be a significant contributor to the contradictory toxicity results observed in the literature for identical NPs, and NP ageing should thus be assessed in parallel with toxicity assessment as best practice.

Application of Bayesian networks for hazard ranking of nanomaterials to support human health risk assessment

“…NM properties driving biological effects have been discussed for a long time (OECD, 2014). Expert consultation prioritized the NM dissolution, shape, reactive surface groups, surface area and size distribution as the most important key descriptors, as observed earlier (Bouwmeester et al, 2011;Izak-Nau et al, 2015). The outcome of our BN model is in line with these findings and showed that the following properties, in decreasing order of importance, were found to be the most important descriptors of the potential hazard of NMs: elemental composition, surface coating, surface area, aggregation and particle size.…”

Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

“…1, what confirmed the presence of AgNPs in all experimental solutions. The colour change is the result of the radiation absorption in the visible region of the electromagnetic spectrum (380 -450 nm) due to the localised surface plasmon of AgNPs [20][21][22]. UV-vis spectra on Fig.…”

“…According to our results and as it was reported earlier [15,[32][33][34], broading and/or symetry loss of SPR band indicates that various shaped and/or sized nanoparticles are present. Izak-Nau et al [20] assumed that such changes in AgNPs' stability under this condition could be attributed to the elevated temperature of the dispersions exposed to daylight, which can increase the NPs collision rate and subsequently induce faster agglomeration. Additionally, daylight can cause photo-reduction of already dissolved Ag + that consequently may lead to the production of new NPs increasing the overall sample polydispersity.…”

Freeze-drying storage method based on pectin for gold nanoparticles

“…[1][2][3][4][5][6][7][8] Agglomeration, precipitation, and even chemical-physical decomposition are commonly observed when aqueous suspension of nanoparticles is stored, [2][3][4]9 forcing to use only freshly prepared nanoparticles, which limits their application in the real world. 5,10,11 Taking into account that the properties of nanoparticles depend on the size, it is highly recommended to use a stabilization method able to avoid agglomeration, even for long storage time.…”