In theory, the smaller the particle size, the higher the specific surface area and the greater bioavailability, which ultimately results in higher toxicity (Adams et al., 2006). Previous studies have shown that nTiO2 obtained from filtration (mean particle size: 30 nm) was much more toxic to D. magna than that obtained via sonication (100–500 nm), with an LC50 value of only 5.5 mg L1 (Lovern and Klaper, 2006). The toxicity of ZnO particles to the gram-positive bacterium Bacillus subtilis showed a decrease with an increase in the particle size of the ZnO (Sawai et al., 1996). Nevertheless, the results of this study indicated that the nanoscale particles were less toxic than the common-scale ones, both for the MN
and NP. It was concluded in previous studies (Adams et al., 2006) that nanoscale particles possess greater biological activity than
common ones. The increase of biological activity produces both
advantages (antioxygenation, enhanced possibilities of cell penetrability
and so on) and disadvantages (stress, inducing the formation
of oxidation and so on) for animals. D. magna may obtain such
advantages when exposed in nanoscale particles suspension, consequently
showing lower toxicosis. However, further research is
required to understand whether it is the size, surface chemistry
or morphology which is the determining factor of the toxicity difference
between the nanoscale and the common-scale particles.
In theory, the smaller the particle size, the higher the specific surface area and the greater bioavailability, which ultimately results in higher toxicity (Adams et al., 2006). Previous studies have shown that nTiO2 obtained from filtration (mean particle size: 30 nm) was much more toxic to D. magna than that obtained via sonication (100–500 nm), with an LC50 value of only 5.5 mg L1 (Lovern and Klaper, 2006). The toxicity of ZnO particles to the gram-positive bacterium Bacillus subtilis showed a decrease with an increase in the particle size of the ZnO (Sawai et al., 1996). Nevertheless, the results of this study indicated that the nanoscale particles were less toxic than the common-scale ones, both for the MNand NP. It was concluded in previous studies (Adams et al., 2006) that nanoscale particles possess greater biological activity thancommon ones. The increase of biological activity produces bothadvantages (antioxygenation, enhanced possibilities of cell penetrabilityand so on) and disadvantages (stress, inducing the formationof oxidation and so on) for animals. D. magna may obtain suchadvantages when exposed in nanoscale particles suspension, consequentlyshowing lower toxicosis. However, further research isrequired to understand whether it is the size, surface chemistryor morphology which is the determining factor of the toxicity differencebetween the nanoscale and the common-scale particles.
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