Interlaboratory comparison of size and surface charge measurements on nanoparticles prior to biological impact assessment
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The International Alliance for NanoEHS Harmonization (IANH) organises interlaboratory comparisons of methods used to study the potential biological impacts of nanomaterials. The aim of IANH is to identify and reduce or remove sources of variability and irreproducibility in existing protocols. Here, we present results of the first IANH round robin studies into methods to assess the size and surface charge of suspended nanoparticles. The test materials used (suspensions of gold, silica, polystyrene, and ceria nanoparticles, with [primary] particles sizes between 10 nm and 80 nm) were first analysed in repeatability conditions to assess the possible contribution of between-sample heterogeneity to the between-laboratory variability. Reproducibility of the selected methods was investigated in an interlaboratory comparison between ten different laboratories in the USA and Europe. Robust statistical analysis was used to evaluate within- and between-laboratory variability. It is shown that, if detailed shipping, measurement, and reporting protocols are followed, measurement of the hydrodynamic particle diameter of nanoparticles in predispersed monomodal suspensions using the dynamic light scattering method is reproducible. On the other hand, measurements of more polydisperse suspensions of nanoparticle aggregates or agglomerates were not reproducible between laboratories. Ultrasonication, which is commonly used to prepare dispersions before cell exposures, was observed to further increase variability. The variability of the zeta potential values, which were also measured, indicates the need to define better surface charge test protocols and to identify sources of variability.
KeywordsNanoparticle Particle surface charge Interlaboratory comparison Reproducibility Polydispersity Toxicology Health and safety implications
The authors are grateful for the input and feedback received from Nancy Corson and Dr. Morton Ehrenberg (Rochester) and Dr. Stijn Put (Umicore). This work was supported through funding from different sources (NCI R01 CA134218 (A.E.), NIEHS RC2 ES018741 (A.E.,G.O.), NSF and EPA EF 0830117, NIEHS R01 ES016746, and NIEHS RC2 ES018766 (A.N.), SFI 07 SRC B1155 (K.D., I.L., S.R.), EU FP6 NanoInteract (KD, IL, SR), federal funds from the National Cancer Institute, National Institutes of Health, contract N01-CO-12400 (S.M., A.P.), German Research Foundation (DFG), Focus Project SPP1313 and EU FP7 Project NeuroNano, NMP4-SL-2008-214547 (W. K.)). The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government or the European Commission.
Conflict of interest
A.R. is an employee of Malvern Corporation, but had no influence on the selection of instruments used in the round robin experiment other than his own. The other authors declare no competing financial interests.
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