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Partial oxidation (“aging”) and surface modification decrease the toxicity of nano-sized zero valent iron
Citation:
Phenrat, T., T. C. Long, G. V. Lowry, AND B. VERONESI. Partial oxidation (“aging”) and surface modification decrease the toxicity of nano-sized zero valent iron . ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 43(1):195-200, (2009).
Impact/Purpose:
The above article examines the effects of oxidation and surface modification on the toxicity of a widely used nanomaterial, zero valent iron (nZVI). Immortalized cells of rodent microglia and neurons are used to rank the oxidative stress response and cytotoxicity of fresh nZVI, “aged”, magnetitie and a poly asapartate surface modified nZVI. A meticulous physicochemical characterization parallels the biological response of these cells to these various versions of nZVI. In addition, high resolution transmission electron microscopy documents the response of the microglia and the neuron to fresh versus surface modified nZVI. Results indicate that fresh nZVI is ocnsistently more toxic to both cell types. Explanations include the higher redox activity of fresh nZVI but also the lower aggregation rate of the surface modified nanomaterial. Such observations continue to link the physical properties of engineer nanoamterials with their biological response.
Description:
Zero-valent iron (nZVI) is a redox-active nanomaterial used for in situ remediation of contaminated groundwater. To assess the effect of “aging” and surface modification on its potential neurotoxicity, cultured rodent microglia and neurons were exposed to fresh nZVI, “aged” (>11 mo) nZVI, magnetite, and polyaspartate surface-modified (SM) nZVI. Increases in oxidative stress and inflammation occurred in BV2 microglia in following rank order: nZVI > “aged” nZVI > magnetite = SM nZVI. ATP levels were reduced in N27 neurons in the following rank order nZVI > SM-nZVI >“aged” nZVI = magnetite. Ultrastructurally, nZVI exposure produced a perinuclear flocular material and cytoplasmic granularity in N27 neurons. In addition, intranuclear deposits of SM-ZVI nanoparticles were documented. The physicochemical properties of each material, measured under exposure conditions indicated that all had electronegative zeta potentials. Sedimentation and agglomeration occurred in the following rank order nZV > ”aged”nZVI > magnetite >> SM-nZVI. Correlating these properties with toxicity indicated that partial or complete oxidation of nZVI decreases its redox activity, agglomeration, sedimentation rate and toxicity to mammalian cells. Surface modification decreased nZVI toxicity by limiting particle exposure to the cells.
