The progressive increase in nanoparticles (NPs) applications and their potential release into the environment because the majority of them end up in the soil without proper care have drawn considerable attention to the public health, which has become an increasingly important area of research. It is required to understand ecological threats of NPs before applications. Once NPs are released into the environment, they are subjected to translocation and go through several modifications, such as bio/geo-transformation which plays a significant role in determination of ultimate fate in the environment. The interaction between plants and NPs is an important aspect of the risk assessment. The plants growing in a contaminated medium may significantly pose a threat to human health via the food chain. Metal oxide NPs ZnO and CuO, the most important NPs, are highly toxic to a wide range of organisms. Exposure and effects of CuO and ZnO NPs on soil biota and human health are critically discussed in this study. The potential benefits and unintentional dangers of NPs to the environment and human health are essential to evaluate and expected to produce less toxic and more degradable NPs to minimize the environmental risk in the future.

ZnO and CuO nanoparticles: a threat to soil organisms, plants, and human health.

Several types of engineered nanoparticles (ENPs) are being considered for direct application to soils to reduce the application and degradation of pesticides, provide micronutrients, control pathogens, and increase crop yields. This study examined the effects of different metal ENPs and their dissolved ions on the microbial community composition and enzyme activity of agricultural soil amended with biosolids. The activity of five extracellular nutrient-cycling enzymes was measured in biosolid-amended soils treated with different concentrations (1, 10, or 100 mg ENP/kg soil) of silver (nAg), zinc oxide (nZnO), copper oxide (nCuO), or titanium dioxide (nTiO2) nanoparticles and their ions over a 30-day period. At 30 days, nZnO and nCuO either had no significant effect on soil enzyme activity or enhanced enzyme activity. In contrast, Ag inhibited selected enzymes when dosed in particulate or dissolved form (at 100 mg/kg). nTiO2 either had no significant effect or slightly decreased enzyme activity. Illumina MiSeq sequencing of microbial communities indicated a shift in soil microbial community composition upon exposure to high doses of metal ions or nAg and negligible shift in the presence of nTiO2. Some taxa responded differently to nAg and Ag+. This work shows how metal ENPs can impact soil enzyme activity and microbial community composition upon introduction into soils amended with biosolids, depending on their type, concentration, and dissolution behavior, hence providing much needed information for the sustainable application of nanotechnology in agriculture.

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Amendment of Agricultural Soil with Metal Nanoparticles: Effects on Soil Enzyme Activity and Microbial Community Composition.

A large number of metallic nanoparticles have been successfully synthesized by using different plant extracts and microbes including bacteria, fungi viruses and microalgae. Some of these metallic nanoparticles showed strong antimicrobial activities against phytopathogens. Here, we summarized these green-synthesized nanoparticles from plants and microbes and their applications in the control of plant pathogens. We also discussed the potential deleterious effects of the metallic nanoparticles on plants and beneficial microbial communities associated with plants. Overall, this review calls for attention regarding the use of green-synthesized metallic nanoparticles in controlling plant diseases and clarification of the risks to plants, plant-associated microbial communities, and environments before using them in agriculture.

Advancements in Plant and Microbe-Based Synthesis of Metallic Nanoparticles and Their Antimicrobial Activity against Plant Pathogens.

Titanium dioxide nanoparticles (nano-TiO2), one of the most produced engineered nanoparticles (ENPs), are used in pigments, photocatalysis, food additives, and personal care products. This broad variety of applications has led to the unusual and widespread distribution of nano-TiO2 in several environmental sectors, with different effects on living organisms. In the last decade, several publications have shown fragments of information about the interaction, detection, uptake, and translocation of nano-TiO2 in plants. This review includes a discussion of the current knowledge about factors affecting the interaction of nano-TiO2 with soil and plants. We also discuss the role of particle size, crystal phase, surface coating, and techniques employed to study the interaction of these nanoparticles with plants. Concluding results from synchrotron based, microscopic, physiological, and biochemical analyses of plants exposed to nano-TiO2 are presented. However, the current information leaves no doubt that there are still many aspects in need of additional investigations to fully understand the effects of nano-TiO2 in plants. For instance, little is known about the transgenerational effects of nano-TiO2 exposure and the changes at agronomical and physiological levels. The effects of such ENPs in proteins and other metabolites are also not well understood. In addition, more information is needed about the interaction of nano-TiO2 with other ENPs-and-organic co-contaminates and the effects of plants. Since nano-TiO2 have been found in edible tissues, it is expected that they will be in the food chain; thus, studies on their trophic transfer are required. The authors hope that, besides contributing to a better understanding of current data about the effects of nano-TiO2 in soil and plants, this review will help to drive future investigations and will contribute to the general knowledge on the environmental interactions of engineered nanomaterials.

Interaction of titanium dioxide nanoparticles with soil components and plants: current knowledge and future research needs – a critical review

http://web2.mendelu.cz/af_239_nanotech/data/pub/Nanoscale%20Copper_N.A.%20Anjum%20et%20al.%20(2015)%20Environmental%20Research.pdf

Nanoscale copper in the soil-plant system - toxicity and underlying potential mechanisms.

With the increased availability of nanoparticle-based products, their releases to soil are undoubtedly inevitable. Among the nanoparticle-based products, potential risks of metal oxide nanoparticles (MO-ENPs) have attracted increasing concerns. However, their effects on soil and soil microorganisms remain largely unknown. In this study, four metal oxide nanoparticles, i.e., zinc oxide nanoparticles (nZnO), titanium dioxide nanoparticles (nTiO2), cerium dioxide nanoparticles (nCeO2), and magnetite nanoparticles (nFe3O4), were enrolled to evaluate their impact on soil enzyme activities (invertase, urease, catalase, and phosphatase) and bacterial communities in two typical soils from northeast China (black soil and saline-alkali soil). The community structure and size were analyzed using pyrosequencing and real-time polymerase chain reaction (RT-PCR). The soils were exposed to metal oxide nanoparticles at 0.5, 1.0, and 2.0 mg g−1 for 15 and 30 days. In general, nZnO had a stronger effect on soil enzymatic activities than nTiO2, nCeO2, and nFe3O4, and saline-alkali soil was more susceptible to metal oxide nanoparticles than black soil. In RT-PCR analysis, a significant decrease (41.66, 36.34, and 47.99%, respectively) on total bacteria population was only observed in saline-alkali soil treated by 0.5, 1.0, and 2.0 mg g−1 nZnO. Meanwhile, pyrosequencing analysis revealed that the samples of saline-alkali soil treated with nZnO showed high variance in their bacterial community composition, e.g., Bacilli, Alphaproteobacteria, and Gammaproteobacteria class. The results suggested that metal oxide nanoparticle incubation could influence soil enzyme activities and change soil bacterial community. Moreover, the soil type was a key component dictating the effect of metal oxide nanoparticles on the bacterial community composition and size. These findings are of great help towards building a comprehensive understanding of the potential environmental risks of metal oxide nanoparticles.

Effects of metal oxide nanoparticles on soil enzyme activities and bacterial communities in two different soil types

The interplay of crystalline packing, which governs atomic length-scale order, and hierarchical assembly, which governs longer length scales, is essential to fabricate complex superstructures from polymers for many applications. Here, we demonstrate that a diblock copolymer containing an N-octylglycine peptoid block, which has a propensity to crystallize, can form distinct hierarchical superstructures including a star-like morphology, a superbrush, or a nanosheet by tuning the balance between surface energy arising from the solubility of the copolymers and crystallization energy of the solvophobic polypeptoid blocks. We show that partially ordered micellar aggregates (clusters) are key intermediates that form early in the assembly process and template the formation of superstructures via the oriented fusion of individual micelles as the growth materials. Notably, the fiber-like branch of the superstructures is driven by crystallization and exhibits growth in a living linear manner. The superstructures can be internalized by mammalian cells and hold promise for biomedical applications.

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Dandan Liu

Papers

Effects of metal oxide nanoparticles on soil enzyme activities and bacterial communities in two different soil types

Hierarchical Approach for Controlled Assembly of Branched Nanostructures from One Polymer Compound by Engineering Crystalline Domains.

Polypeptoid-Assisted Formation of Supramolecular Architectures from Folic Acid for Targeted Cancer Therapy with Enhanced Efficacy.