Comparative toxicity study of Ag, Au, and Ag–Au bimetallic nanoparticles on Daphnia magna

Abstract

A comparative assessment of the 48-h acute toxicity of aqueous nanoparticles synthesized using the same methodology, including Au, Ag, and Ag-Au bimetallic nanoparticles, was conducted to determine their ecological effect in freshwater environments through the use of Daphnia magna, using their mortality as a toxicological endpoint. D. magna are one of the standard organisms used for ecotoxicity studies due to their sensitivity to chemical toxicants. Particle suspensions used in toxicity testing were well-characterized through a combination of absorbance measurements, atomic force or electron microscopy, flame atomic absorption spectrometry, and dynamic light scattering to determine composition, aggregation state, and particle size. The toxicity of all nanoparticles tested was found to be dose and composition dependent. The concentration of Au nanoparticles that killed 50% of the test organisms (LC(50)) ranged from 65-75 mg/L. In addition, three different sized Ag nanoparticles (diameters = 36, 52, and 66 nm) were studied to analyze the toxicological effects of particle size on D. magna; however, it was found that toxicity was not a function of size and ranged from 3-4 μg/L for all three sets of Ag nanoparticles tested. This was possibly due to the large degree of aggregation when these nanoparticles were suspended in standard synthetic freshwater. Moreover, the LC(50) values for Ag-Au bimetallic nanoparticles were found to be between that of Ag and Au but much closer to that of Ag. The bimetallic particles containing 80% Ag and 20% Au were found to have a significantly lower toxicity to Daphnia (LC(50) of 15 μg/L) compared to Ag nanoparticles, while the toxicity of the nanoparticles containing 20% Ag and 80% Au was greater than expected at 12 μg/L. The comparison results confirm that Ag nanoparticles were much more toxic than Au nanoparticles, and that the introduction of gold into silver nanoparticles may lower their environmental impact by lowering the amount of Ag which is bioavailable.

Imposed Environmental Stresses Facilitate Cell-Free Nanoparticle Formation by Deinococcus radiodurans

“…Alternatively, these results could be attributed to the various mechanisms by which silver and silver-containing nanoparticles are toxic. Although AgNPs have been identified within the nuclei of cells as potential DNA-damaging agents, others have suggested the release of Ag ϩ and the subsequent production of reactive oxygen species as the primary mechanism for cell death (50). The latter mechanism is consistent with our observations that Ag-AgNPs and Au-AgNPs demonstrated increased antimicrobial activity, compared to Ag-AuNPs, as the former contain approximately the same amounts of silver and are similar in antimicrobial activity.…”

Biosynthesis of Au, Ag and Au&ndash;Ag bimetallic nanoparticles using protein extracts of <em>Deinococcus radiodurans</em> and evaluation of their cytotoxicity

“…The slight cytotoxicity of Drp-AgNPs could be attributed to the release of Ag and more ROS generation. 38,62 The NPs synthesized by proteins were generally assured to be biocompatible due to the presence of the stabilizing agent. have advantageous applications in biosensors, bioimaging, drug delivery and nanomedicine.…”

Some inferences from in vivo experiments with metal and metal oxide nanoparticles: the pulmonary phagocytosis response, subchronic systemic toxicity and genotoxicity, regulatory proposals, searching for bioprotectors (a self-overview)

“…[1][2][3][4][5][6][7][8][9][10] Although in the vast nanotoxicological literature of the last decade studies concerned with the assessment of metal or metal-oxide NP toxicity are not at the top of the list, such publications are nevertheless quite numerous. To illustrate this, we may refer to several works devoted to NPs of the metals that were the subject-matter of our own studies considered below: iron oxide, [11][12][13][14][15][16][17][18][19][20] silver, gold, 24,[45][46][47][48][49][50][51][52][53][54][55][56][57][58] copper and copper oxide, 43,[59][60][61][62][63][64][65][66][67][68] nickel oxide, 65,[69]…”