Rapid Kinetics of Size and pH-Dependent Dissolution and Aggregation of Silver Nanoparticles in Simulated Gastric Fluid

Abstract

As silver nanoparticles (AgNPs) are used in a wide array of commercial products and can enter the human body through oral exposure, it is important to understand the fundamental physical and chemical processes leading to changes in nanoparticle size under the conditions of the gastrointestinal (GI) tract. Rapid AgNP growth was observed using nanoparticle tracking analysis with 30 s resolution over a period of 17 min in simulated gastric fluid (SGF) to explore rapid kinetics as a function of pH (SGF at pH 2, 3.5, 4.5 and 5), size (20 and 110 nm AgNPs), and nanoparticle coating (citrate and PVP). Growth was observed for 20 nm AgNP at each pH, decreasing in rate with increasing pH, with the kinetics shifting from second-order to first-order. The 110 nm AgNP showed growth at ≤3.5 pH, with no growth observed at higher pH. This behavior can be explained by the generation of Ag+ in acidic environments, which precipitates with Cl−, leading to particle growth and facilitating particle aggregation by decreasing their electrostatic repulsion in solution. These results highlight the need to further understand the importance of initial size, physicochemical properties, and kinetics of AgNPs after ingestion to assess potential toxicity.

Oral uptake of nanoparticles: human relevance and the role of in vitro systems

“…Dissolution of ZnO NPs is much higher than that of TiO 2 particles, and this difference could explain why accumulation in organs was much higher for ZnO than for TiO 2 particles (Cho et al 2013). When dissolution was studied at acid pH, less agglomeration of 10-nm Ag particles were observed than at Table 2 Estimation of minimum and maximum expected doses in the body after dermal, respiratory and oral exposures Area most relevant for absorption is used, and minimum values are based on the assumption of minimum concentration and minimum translocation rate, while maximum values were based on maximum assumed dose and maximal translocation rate * 0.001 % was used as value for trace amounts of translocation ** As minimum value translocation to organs after oral application was used (Bellmann et al 2015 higher pH, while, according to another study, 20-nm Ag suspended in simulated gastric fluid resulted in larger particle sizes (Axson et al 2015;Elzey and Grassian 2010). The contradictory findings could be explained by the composition of the dissolution fluids, nitric acid in the first and hypochloric acid in the second study.…”

DLS and zeta potential – What they are and what they are not?

“…To broaden the scope for applications of NPs, a research-intensive framework within the academia and industry has emerged while attracting significant funding and media attention in last few years [12]. Surface charge and particle size are the two most commonly mentioned factors that are responsible for a range of biological effects of NPs including cellular uptake [13], toxicity [14] and dissolution [15]. Emerging data indicate the influence of these two factors in release profile from NPs designed to carry drug payloads (e.g., macromolecules [16], peptides [17]) and release at target sites (e.g., small intestine [18] for oral drug delivery purposes).…”

Synergistic bactericidal activity of chlorhexidine-loaded, silver-decorated mesoporous silica nanoparticles

“…39 This was because protonation could break surface Ag-O bonds, resulting in more silver ions release into solution at acidic than at neutral pH. 40 Taken together, these findings suggested that Ag-MSNs@CHX exhibited a capability of pH-responsive release of both CHX and silver ions, which might enhance the bactericidal ability. Therefore, we proposed that Ag-MSNs@CHX with pH-sensitive antiseptic release behavior might enhance the antibacterial efficacy in acidic infection foci.…”