Reference materials and representative test materials to develop nanoparticle characterization methods: the NanoChOp project case.

Gert Roebben,Philippe Corbisier,Christian Gollwitzer,Daniel Geißler,Dorota Bartczak,Yannic Ramaye,Julie Davies,Caterina Minelli,Judith Mihály,Stephane Mazoua,Aneta Sikora,Michael Krumrey,James Noble,Neelam Kumarswami,Vikram Kestens,Nele Meeus,Ute Resch‐Genger ,J Cottet ,Zoltán Varga ,Marcell Pálmai ,Heidi Goenaga‐Infante

doi:10.3389/fchem.2015.00056

Abstract

This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a “reference material” (ISO Guide 30, 2015) or rather those of the recently defined category of “representative test material (RTM)” (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use.

Highlights

Most nanoparticles [particles with all external dimensions smaller than 100 nm (ISO/TS 27687, 2008)] are of natural origin or are incidental by-products of human activities, such as engine exhaust particles
This was deduced from the oscillating scattering intensities at higher scattering angles (Figure 2), which facilitate the reliable measurement of dSAXS
centrifugal liquid sedimentation (CLS) results showed a peak near dCLS,i = 14 nm, but the interpretation was inconclusive since this value is close to the lower quantification limit of the method

Summary

Introduction

Most nanoparticles [particles with all external dimensions smaller than 100 nm (ISO/TS 27687, 2008)] are of natural origin or are incidental by-products of human activities, such as engine exhaust particles. Other nanoparticles are produced on purpose to have unique properties and to improve the performance of consumer products. The use of these manufactured nanoparticles leads to their occurrence in the environment and potential exposure of the human body to nanoparticles. The potential health effects of nanoparticles are a cause for concern, and the number of studies to evaluate the toxicity of nanomaterials is increasing. Several authors have questioned the poor reproducibility of data from nanotoxicity studies (Warheit, 2010; Nature Nanotechnology, 2012; Ratna and Shard, 2013; Krug, 2014). One remediating measure is increased interlaboratory collaboration, which is actively supported by, e.g., EU authorities and funding agencies

Methods

Results

Conclusion