EFFECTS FROM FILTRATION, CAPPING AGENTS, AND PRESENCE/ABSENCE OF FOOD ON THE TOXICITY OF SILVER NANOPARTICLES TO DAPHNIA MAGNA

Relatively little is known about the behavior and toxicity of nanoparticles in the environment Objectives of work presented here include establishing the toxicity of a variety of silver nanoparticles (AgNPs) to Daphnia magna neonates assessing the applicability of a commonly used bioassay for testing AgNPs and determining the advantages and disadvantages of multiple characterization techniques for AgNPs in simple aquatic systems Daphnia magna were exposed to a silver nitrate solution and AgNPs suspensions including commercially available AgNPs (uncoated and coated) and laboratory synthesized AgNPs (coated with coffee or citrate) The nanoparticle suspensions were analyzed for silver concentration (microwave acid digestions) size (dynamic light scattering and electron microscopy) shape (electron microscopy) surface charge (zeta potentiometer) and chemical speciation (X ray absorption spectro scopy X ray diffraction) Toxicities of filtered (100 nm) versus unfiltered suspensions were compared Additionally effects from addition of food were examined Stock suspensions were prepared by adding AgNPs to moderately hard reconstituted water which were then diluted and used straight or after filtration with 100 nm filters All nanoparticle exposure suspensions at every time interval were digested via microwave digester and analyzed by inductively coupled argon plasma optical emission spectroscopy or graphite furnace atomic absorption spectroscopy Dose response curves were generated and median lethal concentration (LC50) values calculated The LC50 values for the unfiltered particles were (in mu g/L) 11 +/- 0 1 AgNO3 1 0 +/- 0 1 coffee coated 1 1 +/- 0 2 citrate coated 16 7 +/- 1 2 4 Sigma Aldrich Ag nanoparticles (SA) uncoated 31 5 8 1 SA coated LC50 values for the filtered particles were (in g/L) 0 7 +/- 0 1 AgNO3 1 4 +/- 0 1 SA uncoated 4 4 +/- 1 4 SA coated The LC50 resulting from the addition of food was 176 4 +/- 25 5 SA coated Recommendations presented in this study include AgNP handling methods effects from sample preparation and advantages/disadvantages of different nanoparticle characterization techniques Environ Toxicol Chem 2010 29 2742-2750 (C) 2010 SETAC