Characterization and Potential Migration of Silver Nanoparticles from Commercially Available Food Contact Materials

S. Addo Ntim, T.A. Thomas, T.H. Begley, G.O. Noonan
U.S. Food and Drug Administration, US

Keywords: food contact materials, silver nanoparticles, characterization, migration

Summary:

Nanotechnology is one of the notable science and technological revolutions experienced by the food sector in the last few years. Several food contact products around the globe have reportedly utilized nanomaterials in an attempt to improve packaging performance, impart antimicrobial properties, improve non-stick cookware, and improve biodegradable polymer-nanocomposites. The potential for consumer exposure to nano-components in food contact materials (FCMs) is dependent on the migration of nanomaterials into food. Therefore, characterizing the physico-chemical properties and potential for migration of constituents is an important step in assessing the safety of FCMs. A number of commercially available food storage products, purchased domestically and internationally, which claim to contain nanosilver were evaluated. The FCMs were characterized using a variety of analytical techniques, including Fourier transform infra-red spectroscopy (FTIR), electron microscopy (EM) equipped with energy dispersive spectroscopy (EDS), and inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, silver migration was measured under various conditions, including using 3% acetic acid as a food simulant. The FCMs were made of low density polyethylene (LDPE) and polypropylene (PP) and all contained silver (9-36 mg/kg of polymer). Low concentrations (sub–ppb levels) of silver were detected in the migration studies generally following a trend characterized by a surface desorption phenomenon; where the majority of the silver migration occurred in the first of three consecutive exposures. Migration under non-aqueous conditions did not yield any silver concentrations. EM analysis of the simulant showed the presence of particles which did not show a silver signal in EDS microanalysis, suggesting that the silver detected by ICP-MS may be due solely to ionic silver released into solution from the oxidation of the silver nanoparticle surface. The absence of detectable silver nanoparticles was consistent with expectations from a physico-chemical view point.