Titanium dioxide and table sugar enhance the leaching of silver out of nanosilver packaging

Abstract

We manufactured laboratory-scale food packages containing 2.57 ± 0.18 × 10⁻³ wt% silver nanoparticles (AgNPs) and used them to show that table sugar (sucrose) and microcrystalline titanium dioxide (μTiO₂) enhance Ag migration from these packages and into aqueous food simulants. Ag migration into purified water was detected but was below the limit of ICP-MS quantitation, giving a range of potential Ag migration between 0.059 and 0.082 ng cm⁻² packaging surface area. Ag migration into 9 wt% aqueous sucrose solution was 0.547 ± 0.084 ng cm⁻² and migration into 9 wt% sucrose solution containing 0.01 wt% μTiO₂ was 0.724 ± 0.032 ng cm⁻². Total Ag migration into a 0.01 wt% μTiO₂ aqueous dispersion without sucrose was between 0.122 and 0.162 ng cm⁻², with upper and lower limits defined by the detectability of Ag in the supernatant phase of the simulant. If the midpoint of this range is taken as a baseline, these results imply that, compared to purified water, Ag migration was increased by approximately 10.3 times when the water simulant contained μTiO₂ and sucrose at commercially-relevant concentrations. Notably, the Ag migrated into water containing both ingredients exceeded the total Ag migrated into either of the single-ingredient simulants, pointing to a potential cooperative relationship between sucrose and μTiO₂ that possibly derives from binding and redox interactions between these two ingredients. Sucrose and μTiO₂ also both reduced a portion of migrated Ag⁺ back into AgNPs, and μTiO₂ particles efficiently captured (>25% by mass) migrated Ag on their surfaces. Similar effects on migration were observed with nanocrystalline TiO₂. These experiments are the first to show that TiO₂ particles exert a strong influence on the quantity and form of Ag that could migrate from AgNP-enabled packaging, suggesting that food formulations and interactions between individual food components may be important to consider when evaluating the fate of nanoparticles in these consumer applications.