Delivered by Publishing Technology to: McMaster University IP: 130.113.53.254 On: Fri, 22 Nov 2013 00:26:27 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 1852–1858, 2011 Ecotoxicological Studies of CdS Nanoparticles on Photosynthetic Microorganisms Roberta Brayner 1 * , Si Amar Dahoumane 1 , Julie Ngoc-Lan Nguyen 1 , Claude Yéprémian 2 , Chakib Djediat 2 , Alain Couté 2 , and Fernand Fiévet 1 1 Université Paris Diderot (Paris 7), CNRS, UMR 7086, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), 15 rue Jean de Baïf, F-75205 Paris Cedex 13, France 2 Muséum National d’Histoire Naturelle Département RDDM, USM 505, 57 rue Cuvier, F-75005 Paris, France The potential ecotoxicity of nanosized cadmium sulfide (CdS), synthesized by the polyol process, was investigated using common Anabaena flos-aquae cyanobacteria and Euglena gracilis euglenoid microalgae. The photosynthetic activities of these microorganisms, after addition of free Cd 2+ ions and CdS nanoparticles, varied with the presence of tri-n-octylphosphine oxide (TOPO) used to pro- tect surface particle to avoid toxicity and also to control particle size and shape during the synthesis. The nanoparticle concentration was varied from 10 −3 to 5 · 10 −4 M. It was observed that the cad- mium concentration, the addition of TOPO protective agent and the particle dissolution process in the culture medium play an important role during the ecotoxicological tests. Viability tests were fol- lowed by PAM fluorimetry. Cd 2+ ions were very toxic for Anabaena flos aquae. The same behavior was observed after contact with CdS and CdS-TOPO nanoparticles. However, for Euglena gracilis, the photosynthetic activity was stable for more than 1 month in the presence of Cd 2+ ions. Moreover, it was observed that the toxicity varies with the concentration of CdS and CdS-TOPO nanoparticles, both kind of nanoparticles are toxic for this microorganism. Transmission electron microscopy (TEM) analyses of microorganisms ultrathin sections showed that polysaccharides produced by Anabaena flos-aquae, after contact with CdS and CdS-TOPO nanoparticles, protect the microalgae against particle internalization. Only some particles were observed inside the cells. Moreover, the nanopar- ticle internalization was observed after contact with all nanoparticles in the presence of Euglena gracilis by endocytosis. All nanoparticles are inside vesicles formed by the cells. Keywords: CdS, Microalgae, Ecotoxicology. 1. INTRODUCTION In the last few years, nanoparticles of the group IIb sulfides, MS (M = Zn, Cd, Hg), have attracted a growing interest in a very large fields. Quantum-size sulfides (<10 nm) are well known as quantum dots. These quantum dots nanocrystals are semiconductor, that hold great promise for diverse tech- nologies such as biomedical imaging, targeted gene and drug delivery, solid state lighting, and solar cells. 1–6 There are some studies about the ecotoxicological impact of quan- tum dots nanoparticles on microorganisms. For example, it was shown that quantum dots with intact surface coat- ings (polymaleic anhydride-alt-1-octadecene (PMAO), and polyethylenimine (PEI)) decreased growth rates of Gram positive Bacillus subtilis and Gram negative Escherichia * Author to whom correspondence should be addressed. coli but were not bactericidal. 7 On the other hand, U.S. Environmental Protection Agency test protocol and fluo- rescence microscopy were used to determine the fate and effect of quantum dots having a protective organic coating (Qdot ® 545 ITK ™ Carboxyl Quantum Dots) using stan- dard aquatic test organisms. 8 In this case, no lethality was measured following 48 h exposure of Ceriodaphnia dubia to quantum dots suspensions as high as 110 ppb, but 96 h median lethal concentration to Pseudokirchneriella sub- capitata was measured at 37.1 ppb. Transfer of quantum dots from dosed algae Ceriodaphnia dubia was verified with fluorescence microscopy. In this study, the results indicated that coatings present on nanocrystals provide protection from metal toxicity during laboratory exposures but that the transfer of core metals from intact nanocrystals may occur at levels well above toxic threshold values, indicating the potential exposure of higher trophic levels. 8 1852 J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 3 1533-4880/2011/11/1852/007 doi:10.1166/jnn.2011.3564