Assessment of Crystal Morphology on Uptake, Particle Dissolution, and Toxicity of Nanoscale Titanium Dioxide on Artemia Salina

Assessment of Crystal Morphology on Uptake, Particle Dissolution, and Toxicity of Nanoscale Titanium Dioxide on Artemia Salina

Martha S. Johnson (Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS, USA), Mehmet Ates (Department of Bioengineering, Faculty of Engineering, Munzur University, Tunceli, Turkey), Zikri Arslan (Department of Chemistry, Jackson State University, Jackson, MS, USA), Ibrahim O. Farah (Department of Biology, Jackson State University, Jackson, MS, USA) and Coneliu Bogatu (Environmental Technologies, Timisoara, Romania)
Copyright: © 2017 |Pages: 17
DOI: 10.4018/JNN.2017010102
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Abstract

Knowledge of nanomaterial toxicity is critical to avoid adverse effects on human and environment health. In this study, the influences of crystal morphology on physico-chemical and toxic properties of nanoscale TiO2 (n- TiO2) were investigated. Artemia salina were exposed to anatase, rutile and mixture polymorphs of n-TiO2 in seawater. Short-term (24 h) and long-term (96 h) exposures were conducted in 1, 10 and 100 mg/L suspensions of n-TiO2 in the presence and absence of food. Anatase form had highest accumulation followed by mixture and rutile. Presence of food greatly reduced accumulation. n-TiO2 dissolution was not significant in seawater (p<0.05) nor was influenced from crystal structure. Highest toxic effects occurred in 96h exposure in the order of anatase>mixture>rutile. Mortality and oxidative stress levels increased with increasing n-TiO2 concentration and exposure time (p<0.05). Presence of food in the exposure medium alleviated the oxidative stress, indicating deprivation from food could promote toxic effects of n-TiO2 under long-term exposure.
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Introduction

Our understanding about the environmental and human health effects of nanoscale materials is still in its infancy despite growing research exploring the environmental and biological fate and toxicity of nanomaterials (Scown, van Aerle & Tyler, 2010). This is mainly because the physico-chemical and toxicological properties of materials at nanoscale are a complex phenomenon governed by numerous parameters. Nanomaterials possess very large surfaces (e.g., more atoms per unit area) owing to their extremely small size (1-100 nm), which evidently results in larger contact surfaces and liberation of more toxic elements and ions upon degradation, respectively. Particle size, shape/morphology, surface charge and methods of synthesis also impart significant differences in toxicological properties of nanomaterials (Hu et. al, 2009; Huang, Wu & Aronstam, 2010). Moreover, the physiochemical conditions of test environment (e.g., salinity, pH, temperature, light etc.) and the resilience of model organism may alter observed effects.

Titanium dioxide nanoparticles (n-TiO2) exhibit photocatalytic and antibacterial properties under UV-light (Lai et al., 2008). In recent years, n-TiO2 have been extensively used in various consumer products, including sunscreens, toothpaste, food additives, paints, surface coatings, water disinfection and degradation of pollutants in air and soil (Nowack & Bucheli, 2007; Battin et al., 2009; Weir et al., 2012; Jovanovi, 2015). n-TiO2 is considered an aquatic pollutant due to numerous exterior uses and applications in water treatment. Nevertheless, the information about safety of n-TiO2 to aquatic environments and species is controversial though it is among the earliest nanoscale compounds investigated extensively so far (Jovanovi, 2015). Some groups did not observe any adverse effects on different biological species (Lovern & Klaper, 2006; Lai et al., 2008; Aruoja et al., 2009, Zhu et al., 2011, Fang et al., 2015), while some others reported dose dependent toxic effects (Heinlaan et al., 2008; Zhu et al., 2010; Ates et al., 2013a; Mansfield et al., 2015). For instance, n-TiO2 was reported to be more toxic to microalgae Pseudokirchneriella subcapitata (LC50 = 5.83 mg L–1) than bulk TiO2 (LC50 = 35.9 mg L–1) (Aruoja et al., 2009). In contrast, no apparent toxicity was observed from n-TiO2 to crustaceans Daphnia magna and Thamnocephalus paltyurus, and the bacteria Vibrio fischeri (Heinlaan et al., 2008), but previously exposed Daphnia magna offsprings were found more sensitive to n-TiO2 (Bundschuh et al., 2012). Similarly, aqueous suspensions of n-TiO2 were not acutely toxic but induced oxidative stress on marine abalone (Haliotis diversicolor supertexta) (Zhu et al., 2011). Japanese medaka (Oryzias latipes) embryos showed premature hatching and high mortality from chronic exposure to n-TiO2 (Paterson et al., 2011). Toxicity to rainbow trout (Oncorhynchus mykiss) varied with the route of exposure (Handy et al., 2008). Direct exposure to n-TiO2 colloids caused severe adverse effects whereas no acute toxicity was detected from dietary exposure.

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