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Cd2+ Toxicity to a green alga Chlamydomonas reinhardtii as influenced by its adsorption on TiO2 engineered nanoparticles.

Yang WW, Miao AJ, Yang LY - PLoS ONE (2012)

Bottom Line: A pseudo-first order kinetics was found for the time-related changes in the amount of Cd(2+) complexed with TiO(2)-ENs.Algal growth was less suppressed in treatments with comparable total Cd(2+) concentration but more TiO(2)-ENs.No detectable amount of TiO(2)-ENs was found to be associated with the algal cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, China.

ABSTRACT
In the present study, Cd(2+) adsorption on polyacrylate-coated TiO(2) engineered nanoparticles (TiO(2)-ENs) and its effect on the bioavailability as well as toxicity of Cd(2+) to a green alga Chlamydomonas reinhardtii were investigated. TiO(2)-ENs could be well dispersed in the experimental medium and their pH(pzc) is approximately 2. There was a quick adsorption of Cd(2+) on TiO(2)-ENs and a steady state was reached within 30 min. A pseudo-first order kinetics was found for the time-related changes in the amount of Cd(2+) complexed with TiO(2)-ENs. At equilibrium, Cd(2+) adsorption followed the Langmuir isotherm with the maximum binding capacity 31.9, 177.1, and 242.2 mg/g when the TiO(2)-EN concentration was 1, 10, and 100 mg/l, respectively. On the other hand, Cd(2+) toxicity was alleviated in the presence of TiO(2)-ENs. Algal growth was less suppressed in treatments with comparable total Cd(2+) concentration but more TiO(2)-ENs. However, such toxicity difference disappeared and all the data points could be fitted to a single Logistic dose-response curve when cell growth inhibition was plotted against the free Cd(2+) concentration. No detectable amount of TiO(2)-ENs was found to be associated with the algal cells. Therefore, TiO(2)-ENs could reduce the free Cd(2+) concentration in the toxicity media, which further lowered its bioavailability and toxicity to C. reinhardtii.

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The transmission electron microscope image of TiO2-ENs dispersed in the modified WC medium (WCm) (a) and their zeta potentials (mV) at different pH (b).
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pone-0032300-g001: The transmission electron microscope image of TiO2-ENs dispersed in the modified WC medium (WCm) (a) and their zeta potentials (mV) at different pH (b).

Mentions: The TiO2-ENs used in the present study were coated with sodium polyacrylate and could thus be well dispersed in WCm as supported by their TEM images shown in Fig. 1a. Their diameter was 46.6 nm on average by measuring 1000 particles randomly chosen from the copper grids, which was consistent with what was obtained by DLS (19.0–46.8 nm). The relatively good dispersibility of TiO2-ENs coated by the polyelectrolyte could be explained by their much lower pHpzc (Fig. 1b), at which a particle surface has zero net electrical charge, than that of their naked counterpart (pHpzc = 2 vs. 6) [22], [23]. Such decrease in pHpzc was mainly caused by polyacrylate's ability to push the slip plane of the crystal lattice away from the ENs, change their charge distribution in the diffusion layer and block the active sites on the TiO2-EN surface as well [23]. Furthermore, the extent of the shift in pHpzc was determined by both the concentration and molecular weight of polyacrylates. Despite their good dispersibility in WCm, the actual diameter of TiO2-ENs was much bigger than what was reported by the manufacturer (1–10 nm) suggesting the electric double layer of the primary nanoparticles was compressed in the adsorption medium with the ionic strength 2.65×10−3 M and aggregates were thus formed. The presence of divalent cations like Ca2+ (0.25 mM) and Mg2+ (0.15 mM) in WCm could further destabilize the TiO2-EN suspension [1].


Cd2+ Toxicity to a green alga Chlamydomonas reinhardtii as influenced by its adsorption on TiO2 engineered nanoparticles.

Yang WW, Miao AJ, Yang LY - PLoS ONE (2012)

The transmission electron microscope image of TiO2-ENs dispersed in the modified WC medium (WCm) (a) and their zeta potentials (mV) at different pH (b).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3293805&req=5

pone-0032300-g001: The transmission electron microscope image of TiO2-ENs dispersed in the modified WC medium (WCm) (a) and their zeta potentials (mV) at different pH (b).
Mentions: The TiO2-ENs used in the present study were coated with sodium polyacrylate and could thus be well dispersed in WCm as supported by their TEM images shown in Fig. 1a. Their diameter was 46.6 nm on average by measuring 1000 particles randomly chosen from the copper grids, which was consistent with what was obtained by DLS (19.0–46.8 nm). The relatively good dispersibility of TiO2-ENs coated by the polyelectrolyte could be explained by their much lower pHpzc (Fig. 1b), at which a particle surface has zero net electrical charge, than that of their naked counterpart (pHpzc = 2 vs. 6) [22], [23]. Such decrease in pHpzc was mainly caused by polyacrylate's ability to push the slip plane of the crystal lattice away from the ENs, change their charge distribution in the diffusion layer and block the active sites on the TiO2-EN surface as well [23]. Furthermore, the extent of the shift in pHpzc was determined by both the concentration and molecular weight of polyacrylates. Despite their good dispersibility in WCm, the actual diameter of TiO2-ENs was much bigger than what was reported by the manufacturer (1–10 nm) suggesting the electric double layer of the primary nanoparticles was compressed in the adsorption medium with the ionic strength 2.65×10−3 M and aggregates were thus formed. The presence of divalent cations like Ca2+ (0.25 mM) and Mg2+ (0.15 mM) in WCm could further destabilize the TiO2-EN suspension [1].

Bottom Line: A pseudo-first order kinetics was found for the time-related changes in the amount of Cd(2+) complexed with TiO(2)-ENs.Algal growth was less suppressed in treatments with comparable total Cd(2+) concentration but more TiO(2)-ENs.No detectable amount of TiO(2)-ENs was found to be associated with the algal cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu Province, China.

ABSTRACT
In the present study, Cd(2+) adsorption on polyacrylate-coated TiO(2) engineered nanoparticles (TiO(2)-ENs) and its effect on the bioavailability as well as toxicity of Cd(2+) to a green alga Chlamydomonas reinhardtii were investigated. TiO(2)-ENs could be well dispersed in the experimental medium and their pH(pzc) is approximately 2. There was a quick adsorption of Cd(2+) on TiO(2)-ENs and a steady state was reached within 30 min. A pseudo-first order kinetics was found for the time-related changes in the amount of Cd(2+) complexed with TiO(2)-ENs. At equilibrium, Cd(2+) adsorption followed the Langmuir isotherm with the maximum binding capacity 31.9, 177.1, and 242.2 mg/g when the TiO(2)-EN concentration was 1, 10, and 100 mg/l, respectively. On the other hand, Cd(2+) toxicity was alleviated in the presence of TiO(2)-ENs. Algal growth was less suppressed in treatments with comparable total Cd(2+) concentration but more TiO(2)-ENs. However, such toxicity difference disappeared and all the data points could be fitted to a single Logistic dose-response curve when cell growth inhibition was plotted against the free Cd(2+) concentration. No detectable amount of TiO(2)-ENs was found to be associated with the algal cells. Therefore, TiO(2)-ENs could reduce the free Cd(2+) concentration in the toxicity media, which further lowered its bioavailability and toxicity to C. reinhardtii.

Show MeSH
Related in: MedlinePlus