Two concentrations of polyvinylpyrrolidone (PVP)-coated silver nanoparticle dispersions were evaluated and used to spike chicken meat.
The aim was to produce a set of reference materials to support development of analytical methods for detection and quantification of nanoparticles in food.
Aqueous silver nanoparticle (AgNP) dispersions were evaluated for homogeneity of mass fraction and particle size and found sufficient to be used as reference materials.
Rapid freezing over liquid nitrogen resulted in homogeneous and stable materials.
The observed differences in particle sizes between the spiked chicken samples and the original silver dispersions indicate relevant matrix effects, said the researchers.
Stability studies at 4 °C, 18 °C and 60 °C demonstrated sufficient short- and long-term stability, although particle size decreases in a linear fashion at 60 °C, they added.
NanoLyse EU project
EU Regulation 1169/2011 requires food producers to inform consumers whether ingredients are present in nano-form.
Silver nanoparticles in a meat matrix were chosen as one model system of the FP7 Project NanoLyse, which looked at the development of methods for detection and quantification of nanoparticles in food.
NanoLyse was a 45 month project which began in 2010.
Scientists of the JRC-Institute for Reference Materials and Measurements (IRMM) produced the first reference materials for detection and quantification of silver nanoparticles in a food matrix.
For the production of the materials, a suspension of nanoparticles in water was mixed with chicken meat puree and shock-frozen in liquid nitrogen at -150 °C.
This resulted in a homogeneous material with only moderate agglomeration of silver nanoparticles.
There are no reference materials for the detection and quantification of nanoparticles in food commercially available, according to the study.
Stability is one of the critical steps as AgNPs are known to be susceptible to dissolution and agglomeration.
Materials developed in the study can serve as a first step towards improving analytical methods and developing certified reference materials, said the researchers.
Suitable reference material and analytical methods
As no detectable changes were observed over six months, it was concluded the material is qualified to serve as a reference material.
However, the detection of quantification of the nano silver particles in the material still poses a challenge due to the lack of suitable analytical methods.
The AgNP dispersions were characterized for Ag mass fraction by ICP-OES, dissolved Ag content by ultrafiltration-ICP-MS, AgNP particle size by dynamic light scattering, transmission electron microscopy (TEM) and gas-phase electrophoretic molecular mobility analysis.
Chicken breasts were homogenized by cryo-milling and spiked with aqueous AgNP. The leanness was expected to minimise problems in homogenizing and mixing.
“This paper describes processing and characterization of two aqueous AG dispersions and two AgNP-spiked chicken meat reference materials, together with the challenges caused by the fact that methods were developed simultaneously with the reference material.”
Source: Accreditation and Quality Assurance, February 2015, volume 20, issue 1, pages 3-16
Online ahead of print, DOI: 10.1007/s00769-014-1100-5
“Feasibility of the development of reference materials for the detection of Ag nanoparticles in food: neat dispersions and spiked chicken meat”
Authors: Ringo Grombe, Günter Allmaier, Jean Charoud-Got, Agnieszka Dudkiewicz, Håkan Emteborg, Thilo Hofmann, Erik Huusfeldt Larsen, Angela Lehner, Meritxell Llinàs, Katrin Loeschner, Kristian Mølhave, Ruud J. Peters, John Seghers, Conxita Solans, Frank von der Kammer, Stephan Wagner, Stefan Weigel, Thomas P. J. Linsinger