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Characterization of nanomaterial test solutions for terrestrial plant dose-response studies: A comparative study of DLS and SAXS
Citation:
Betts, J. N., M. PLOCHER, L. Tumburu, M. G. JOHNSON, G. KING, P. T. RYGIEWICZ, AND C. P. ANDERSEN. Characterization of nanomaterial test solutions for terrestrial plant dose-response studies: A comparative study of DLS and SAXS. Presented at SETAC, Boston, MA, November 13 - 17, 2011.
Impact/Purpose:
Industrial applications of nanomaterials have expanded at an increasing rate in recent years, accompanied by the need for comprehensive toxicological assessments to establish environmental health and safety standards.
Description:
Industrial applications of nanomaterials have expanded at an increasing rate in recent years, accompanied by the need for comprehensive toxicological assessments to establish environmental health and safety standards. Relatively few studies have examined the effects of nanoparticles on terrestrial plants, and the studies that have been done often provide incomplete characterization of particle solutions, making replication and interpretation difficult. In order to fully assess the potential effects of nanoparticle exposure, it is imperative that solutions are fully characterized and exposure protocols are well documented. Preliminary results from an Arabidopsis thaliana Co-O seed germination trial performed with titanium dioxide (TiO2) nanoparticles (NP) with five concentrations [0.1-1000 ppm] suggested an apparent retardation in cotyledon expansion at 10 ppm and slowest seed germination at 1000 ppm. It was difficult to interpret these results, however, because despite identical mixing protocols, concentration was not the only factor that differed among our various test solutions. To address this problem, a comparative study of pre-exposure characterization techniques (Dynamic light scattering/Electrophoretic light scattering [DLS/ELS] & Small-angle X-Ray Scattering [SAXS]) was performed in conjunction with an A.thaliana plant exposure study. Nanomaterial properties including mean particle size, particle size distribution (PSD), and suspension stability at various particle abundances were compared. Initial results of TiO2-NP suspensions using DLS/ELS suggested an increase in dispersion stability at higher concentrations, which could confound dose-response studies. Such findings highlight the need to consider the constraints associated with characterizing solutions based only on light-scattering measurements. Our results will help to quantify observable differences in physico-chemical characteristics due to variable particle abundance, leading to a better understanding of the limitations of each measurement technique in order to establish more comprehensive and accurate methods for characterizing nanomaterial test solutions for toxicological studies.