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There is a great deal of concern about the safety of nanoparticles and their effect on the environment; this has led to a recent Organisation for Economic Co-operation and Development (OECD) drive for testing the toxicity of industrially relevant nanomaterials. A fundamental aspect of the research is the need to measure particle size and particle concentration accurately and reliably, as these two parameters will infl uence toxicity. The current paper presents a study that aims to characterise CeO2 nanoparticles for the purpose of ecotoxicological studies, and this has resulted in a two-part study that is presented in this paper. The aim of the fi rst part of the study was to observe if small nanosized clusters (<1 μm) existed when dispersed in four ecotoxicological media (i.e. fi sh, daphnia, seawater and de-ionised water); this was done qualitatively using Scanning Electron Microscopy. The second part of the study aimed to explore the feasibility of Nanoparticle Tracking Analysis (NTA) as a suit-able tool to characterise not only particle size but also particle number concentration. This involved dispersing CeO2 in DI water and diluting the stock solution into nine different concentrations. Particle size and number data were then acquired using NTA; particle size data were compared to the corresponding Dynamic Light Scattering (DLS) response. The results were as follows: (a) although the majority of the nanomaterials were large aggregates (at least few microns in dimensions), smaller clusters (<800 nm) were shown to be present in all four media; it is the fate of these small size clusters that should be monitored if hypothesis relating toxicity to particle size holds true, (b) as a tool NTA yielded small particle size compared to DLS measurements and the limit of quantifi cation is shown to be >0.1 mg/L, as NTA tracks individual particles and does not suffer limitations observed with DLS, in which larger particles can potentially mask signal of smaller particles and (c) calibration curve for number concentration by NTA did not yield a linear response; the non-linear response observed should be further investigated if NTA is going to be used to measure particle number concentration, particularly in the low concentration range.
Agglomerates, aggregation, aquatic ecotoxicity, CeO2, characterisation, dispersion, DLS, nanoparticles, NTA, SEM
[1] Maynard, A.D. & Pui, D.Y.H., Nanotechnology and occupational health: new technologies – new challenges. Journal of Nanoparticle Research, 9(1), pp. 1–3, 2007. doi:10.1007/s11051-006-9164-8
[2] Tantra, R., Jing, S. & Gohil, D., Technical issues surrounding the preparation, characterization and testing of nanoparticles for ecotoxicological studies. Environmental Toxicology 3, ed. V.B. Popov, C.A, WIT Press, pp. 165–176, 2010.
[3] Tiede, K. et al., Detection and characterization of engineered nanoparticles in food and the environment. Food Additives and Contaminants, 25(7), pp. 795–821, 2008. doi:10.1080/02652030802007553
[4] Lundqvist, M., Stigler, J., Elia, G., Lynch, I., Cedervall, T. & Dawson, K.A., Nanoparticle size and surface properties determine the protein corona with possible implications for biological impacts. Proceedings of the National Academy of Sciences of the United States of America, 105(38), pp. 14265–14270, 2008. doi:10.1073/pnas.0805135105
[5] Tantra, R., Tompkins, J. & Quincey, P., Characterisation of the de-agglomeration effects of bovine serum albumin on nanoparticles in aqueous suspension. Colloids and Surfaces B: Biointerfaces 75, pp. 275–281, 2010. doi:10.1016/j.colsurfb.2009.08.049
[6] Handy, R.D. et al., The ecotoxicology and chemistry of manufactured nanoparticles. Ecotoxicology, 17(4), pp. 287–314, 2008. doi:10.1007/s10646-008-0199-8
[7] Karakoti, A.S., Hench, L.L. & Seal, S., The potential toxicity of nanomaterials – the role of surfaces. Jom, 58(7), pp. 77–82, 2006. doi:10.1007/s11837-006-0147-0
[8] Oberdörster, G. et al., Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy. Particle and Fibre Toxicology, 2, p. 8, 2005. doi:10.1186/1743-8977-2-8
[9] Lowell, S., Shields, J.E., Thomas, M.A. & Thommes, M., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density (Particle Technology Series), Springer, 1st edn. 2004. Corr. 2nd printing edition, 2006.
[10] Zheng, Z.K. et al., Research on laser induced breakdown spectroscopy for detection of trace Cu in polluted soil. Spectroscopy and Spectral Analysis, 29(12), pp. 3383–3387, 2009.
[11] Jung, E.C. et al., Nanoparticle sizing by a laser-induced breakdown detection using an optical probe beam defl ection. Applied Physics B-Lasers and Optics, 97(4), pp. 867–875, 2009. doi:10.1007/s00340-009-3780-9
[12] Filipe, V., Hawe, A. & Jiskoot, W., Critical evaluation of nanoparticle tracking analysis (NTA) by nanosight for the measurement of nanoparticles and protein aggregates. Pharmaceutical Research, 27(5), pp. 796–810, 2010. doi:10.1007/s11095-010-0073-2
[13] Hosokawa, M. et al., Nanoparticle Technology Handbook, Elsevier: Amsterdam, 2007.
[14] Leapman, R.D. & Hunt, J.A., Comparison of detection limits for Eels and Edxs. Microscopy Microanalysis Microstructures, 2(2–3), pp. 231–244, 1991. doi:10.1051/mmm:0199100202-3023100
[15] Malvern Instruments Ltd., Technical information provided for the Zeta-sizer Nano.
[16] Berne, B.J. & Pecora, R., Dynamic Light Scattering: with Applications to Chemistry, Biology, and Physics, Unabridged edition, Dover Publications, 2000.
[17] Hubbard, A.T., Encyclopedia of Surface and Colloid Science, New York Marcel Dekker: New York, 2002.
[18] Kissa, E.E., Dispersions: Characterization, Testing, and Measurement, Marcel Dekker, New York, 1999.
[19] Hiemenz, P.C. & Rajagopalan, R., Principles of Colloid and Surface Chemistry (Hardcover), Marcel Dekker, New York, 1997.
[20] Simonet, B.M. & Valcarcel, M., Monitoring nanoparticles in the environment. Anal Bioanal. Chem., 393, pp. 17–21, 2009. doi:10.1007/s00216-008-2484-z
[21] Tantra, R., Schulze, P. & Quincey, P., The effect of nanoparticle concentration on zeta-potential meausurement results and reproducibility. Particuology, 8, pp. 279–285, 2010. doi:10.1016/j.partic.2010.01.003
[22] Malloy, A. & Carr, B., Nanoparticle tracking analysis – the Halo (TM) system. Particle & Particle Systems Characterization, 23(2), pp. 197–204, 2006. doi:10.1002/ppsc.200601031
[23] Nanosight, Technical Note M500B How to make Concentration Measurements using NanoSight LM Series Instruments, 2009.
[24] Oberdorster, G., Oberdorster, E. & Oberdorster, J., Concepts of nanoparticle dose metric and response metric. Environmental Health Perspectives, 115(6), pp. A290, 2007. doi:10.1289/ehp.115-a290a