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Tag Archives: Toxicology
“Stabilization or Oxidation of Nanoscale Zerovalent Iron at Environmentally Relevant Exposure Changes Bioavailability and Toxicity in Medaka Fish” Chen, P-J; Tan, S-W; Wu, W-L. Environ. Sci. Technol. 2012, ASAP. DOI: 10.1021/es3006783
We’ve posted before on iron-catalyzed reactions (see here for a recent post) as greener alternatives to more traditional platinum group catalyzed reactions. However, even iron has toxicity concerns as described in this paper from National Taiwan University on the toxicity in medaka fish of zerovalent iron (nZVI) nanoparticles (NPs). This is particularly pertinent research in light of the increased usage of iron(0) nanomaterials in remediation.
The study investigates the effects of four different iron dosing ‘solutions’ on the molecular, cellular and organismal health of medaka larvae: (i) carboxymethylcellulose stabilized nZVI (CMC-nZVI), (ii) non-stabilized nZVI (nZVI), (iii) magnetite NPs (nFe3O4), and (iv) soluble Fe(II).
They first characterize the dosing solutions. The sizes of their nanoparticles are 75 nm, 25-75 nm, and 27 nm for CMC-nZVI, nZVI, and nFe3O4 respectively. The zeta potentials were measured to show, not surprisingly, that the CMC-stabilized particles are much more stable to aggregation than the non-stabilized nZVI.
Interestingly, of the four iron dosing solutions, CMC-nZVI has the most significant impact on the level of dissolved oxygen, decreasing it to zero where it remained for 12 hours. Furthermore, this aerobic oxidation of CMC-nZVI leads to a release of 45 mg/L of soluble Fe(II) in 10 min from an initial concentration of 100 mg/L CMC-nZVI as well as an increase in reactive oxygen species (ROS). In contrast, nZVI and nFe3O4 are 20 – 40 % aggregated within 10 min and release less than 20 mg/L of Fe(II) during this time. Only nZVI induces the production of ROS with nFe3O4 and soluble Fe(II) showing no increase in ROS relative to the control. The following figure details these findings for CMC-nZVI; analogous graphs are found in the supplementary information for the other solutions.
“Towards Rational Molecular Design for Reduced Chronic Aquatic Toxicity” Voutchkova-Kostal, A. M.; Kostal, J.; Connors, K. A.; Brooks, B. W.; Anastas, P. T.; Zimmerman, J. B. Green Chem. 2012, 14, 1001-1008. DOI: 10.1039/C2GC16385C
As a synthetic chemist with little (actually zero) training in toxicology, it’s difficult for me to imagine how to design safer chemicals at the start of a project. I can avoid nasty solvents, use safer reagents, but when designing a new molecule I haven’t a clue of its potential toxicological impact. This is frustrating and as the authors of the above paper in Green Chemistry point out, “with the growing number of new chemicals being introduced into the market, it is not economically or ethically reasonable to assume that each can undergo systematic toxicological testing […]”. Thus, possessing a set of easy-to-implement synthetic guidelines to reduce the toxicity of a synthetic target during the design stage, while maintaining (or better yet, augmenting) its function, is of high importance.
Recently, the Zimmerman group reported on guidelines for reducing acute aquatic toxicity and have now extended their work to chronic aquatic toxicity. This is an important next step because chronic toxicity studies are necessarily longer-term (and thus more resource intensive) than acute toxicity studies.
In the current work, they explore the relationships between 38 physicochemical properties of 865 chemicals with chronic aquatic toxicity toward three model organisms: the Japanese medaka, a cladoceran, and a green algae. The 38 properties include, for example, molecular weight, number of freely rotatable bonds, aqueous solubility, and number of hydrogen bond donors and acceptors. (more…)
“Application of the Hard and Soft, Acids and Bases (HSAB) Theory to Toxicant–Target Interactions” LoPachin, R. M.; Gavin, T; DeCaprio, A.; Barber, D. S. Chem. Res. Toxicol. 2012, 25, 239-251. DOI: 10.1021/tx2003257
I considered posting about the Carreira group‘s work on enantioselective amination of allylic alcohols, because I think it is an awesome example of direct functionalization of hydroxylated substrates–an issue that will be of increasing importance in terms of biomass utilization. However I chose instead to stray into the less familiar territory of the bioactivity of organic molecules. I am semi-familiar with quantitative structure activity relationship (QSAR) modeling, wherein a database of known molecules and their bioactivity is used to predict the bioactivity of a molecule about which there is no bioactivity data. However, relying solely on computers leaves me wanting a more intuitive grasp on which molecules are expected to be toxic/non-toxic and why. That’s why I got excited about the recent perspective article about using the familiar Hard-Soft Acid-Base theory to predict toxicant-target interactions.
“Dioxins: An Overview and History” Hites, R. A. Environ. Sci. Technol. 2010, ASAP. DOI 10.1021/es1013664
One of my main reasons for drinking the green chemistry kool-aid is that I believe it allows me to still do cool chemistry as well as to contribute to building a more sustainable civilization (at least that’s the idea). The focus, in my eyes, is on the positive things you can do with chemistry. However, as the Spanish-American philosopher George Santayana first said, “Those who cannot remember the past are condemned to repeat it.” With that in mind, this post is about one of the most well-studied mistakes in the history of the chemical enterprise, polychlorinated dibenzo-p-dioxins (PCDDs), often referred to collectively in the literature as dioxins. In Ronald Hites’ recent ES&T feature article on dioxins, he tells the story of the most toxic of the 75 dioxin congeners, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD).
The most sinister aspect of dioxins, from a chemists’ perspective, is the (more…)
“Quantification of Water Solubilized CdSe/ZnS Quantum Dots in Daphnia magna” N. A. Lewinski, H Zhu, H J Jo, D. Pham, R R Kamath, C R Ouyang, C D Vulpe, V L Colvin, and R A Drezek. Environ. Sci. Technol. 2010, 1841-1846. 10.1021/es902728a
“Quantum Dot Weathering Results in Microbial Toxicity” S Mahendra, H Zhu, V L Colvin, P J Alvarez. Environ. Sci. Technol. 2008, 9424-9430. 10.1021/es8023385
The goal of green chemistry is to design chemicals and chemical processes which are inherently less toxic. For the emerging discipline of nanoscience, the potential toxicological properties remain largely unknown. That said I would like to discuss two related articles concerning the fate and toxicity of nanoparticles (NPs) in the aquatic environment. I like this set of articles because they are both simple, and yet give a hint of the complexities involved with understanding NP fate and toxicity. The more recent, examines the interaction between CdSe/ZnS NPs with Daphnia (a model species for aquatic toxicity). And the original article that drew my attention to this work concerned the same NP and studies the effect that chemical degradation has on NP toxicity. (more…)