Critical Review pubs.acs.org/est
Toxicity, Uptake, and Translocation of Engineered Nanomaterials in Vascular plants Pola Miralles, Tamara L. Church, and Andrew T. Harris*
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Laboratory for Sustainable Technology, School of Chemical and Biomolecular Engineering, University of Sydney, NSW 2006, Australia ABSTRACT: To exploit the promised benefits of engineered nanomaterials, it is necessary to improve our knowledge of their bioavailability and toxicity. The interactions between engineered nanomaterials and vascular plants are of particular concern, as plants closely interact with soil, water, and the atmosphere, and constitute one of the main routes of exposure for higher species, i.e. accumulation through the food chain. A review of the current literature shows contradictory evidence on the phytotoxicity of engineered nanomaterials. The mechanisms by which engineered nanomaterials penetrate plants are not well understood, and further research on their interactions with vascular plants is required to enable the field of phytotoxicology to keep pace with that of nanotechnology, the rapid evolution of which constantly produces new materials and applications that accelerate the environmental release of nanomaterials.
subject to quantum confinement, that is, the energy levels of an ENM are quantized at values directly related to its size.15 A recent inventory found thousands of ENM-related products currently available,16 and their market presence is predicted to grow, due both to the delivery of new technologies and the elaboration of present technologies. This anticipated proliferation of ENM-related products, especially in the areas of nanomedicine and nanofoods, has raised concerns about the potential toxicity of ENMs.17−19 Both the scientific community and governmental agencies have become aware that the physicochemical properties specifically valued in ENMs higher specific surface area and enhanced reactivity, strength, and electrical conductivitycould pose new and unanticipated environmental and health risks. ENMs can be released into the environment deliberately or accidentally. Intentional ENM releases include their use in water purification and remediation,20,21 for groundwater and soil remediation,22 as delivery systems in agriculture,23−25 as biosensors,26 and from medical 27−29 and cosmetic30,31 applications. ENMs could be accidentally released via atmospheric emissions, by leaching from sewage sludge, or from the erosion of ENM-containing materials during use.29,32,33 According to the “cradle to grave” approach,13,17,21 all of the impacts of a technology, from manufacturing to disposal, are relevant to its sustainability.
The interactions between vascular plants and engineered nanomaterials (ENMs) can shed light on the environmental consequences of nanotechnology. Nevertheless, relatively few studies have examined the mechanism(s) of ENM phytotoxicity and bioaccumulation. Collaborations among materials scientists, biologists, and toxicologists are needed to optimize the applications of ENMs while minimizing their health and environmental impacts. Reviews of the current knowledge on ENM−plant interactions have been published recently,1−9 as have ENM-specific reviews that include data on the interactions of plants with CNTs10 and other carbon nanomaterials11 and with TiO2.12 Nevertheless, the rapid pace of nanotechnology research and product development, as well as the potential for significant impacts to the environment and to human health, compel further investigations on the bioavailability and behavior of ENMs in higher plant systems, as well as regular reviews of this research. The objective of this review is to extend our current understanding of ENM phytotoxicity, both in vitro and in vivo, and to describe the possible mechanisms for ENM bioaccumulation.
1. NANOTECHNOLOGY AND ENGINEERED NANOMATERIALS Nanotechnology encompasses the design, production, characterization, and application of structures and systems at the nanometer scale.13 An ENM is a material that measures 97% purity, diameter 20−100 nm, SSA >14 m2/g. ∼90 ppm. AD 11.7 ± 0.6 nm. 2000 mg/L.
0.2−4%d
No effect on germination. Inhibition of root elongation.
No effect on germination. Inhibition of root elongation. No effect on germination. Inhibition of root elongation.
AD 21.8 ± 2.7 nm. 2000 mg/L.
99.5% purity, diameter
