Interactions, Transformations, and Bioavailability of Nano-Copper Exposed to Root Exudates

Abstract

Due to the potential for interactions between crop plants and engineered nanomaterials (ENMs), there is increasing interest in understanding the bioavailability and effects of ENMs released into soil systems. Here, we investigate the influence of root exudates on the fate of ENMs from a thermodynamic perspective. Nano isothermal titration calorimetry was applied to determine thermodynamic parameters for the interaction between nanocopper (nCu) and synthetic root exudate (SRE) and its components (including sugars, organic acids, amino acids, and phenolic acids), as well as Cu2+ and SRE. The measured binding constant (K d = 5.645 × 103 M–1) indicated strong interactions between nCu particles and SRE, as well as with individual organic acids. The interaction between Cu2+ and SRE was stronger (K d = 7.181 × 104 M–1) but varies for the individual SRE components. nCu dissolution in the presence of SRE was the predominant interaction. In addition, SRE resulted in a complex transformation of nCu, where Cu2+, Cu+, and Cu0 were formed via oxidation and reduction. Plant–nCu exposure experiments indicate that the binding of SRE with nCu and dissolved Cu ions can significantly decrease Cu uptake and bioaccumulation in plants. nITC provides a fundamental thermodynamic understanding of interactions between nCu and plant root exudates, providing an important tool for understanding plant NP-interactions.

Metal based nanoparticles in agricultural system: behavior, transport, and interaction with plants

“…Recent study conducted by Huang et al indicated synthetic root exudates can promote Cu NPs dissolution rate and increase the bioavailability of free Cu ion in the soil systems. [88] For different plants organic matter composition in rhizosphere, therefore their effects on metal based NPs are different. Judy et al [89] studied bioavailability of Gold NPs to plants indicating the differences in root exudates between wheat and tobacco resulted into different aggregation of Gold NPs, affecting their bioavailability to plants.…”

Physical Properties of Carbon Nanomaterials and Nanoceria Affect Pathways Important to the Nodulation Competitiveness of the Symbiotic N2‐Fixing Bacterium Bradyrhizobium diazoefficiens

“…[32] RE have also been shown to alleviate the toxicity of metal-based ENMs, due to complexation with harmful metals. [33,34] However, the ENMs in this study were either carbon based or likely insoluble in the experimental media. Thus, the RE-caused mitigation of ENMs' growth inhibitory effects was not likely to have been via toxic ion sequestration.…”

Interaction of Copper-Based Nanoparticles to Soil, Terrestrial, and Aquatic Systems: Critical Review of the State of the Science and Future Perspectives

“…Significant reduction of CuO-NPs to Cu 2 S and Cu 2 O was also shown in maize during rootshoot-root translocation of CuO-NPs (Wang et al 2012). The reason behind the transformation of Cu(II) to Cu (I) in plants may be ascribed to the presence of reducing sugars which get transported from leaf cells to roots (Huang et al 2017;Servin et al 2017a).…”

“…Interaction of Cu-NPs with plant root exudates also influences the fate of Cu-NPs and magnitude of toxicity. Huang et al (2017) determined the thermodynamic parameters for the interaction of Cu-NPs (40 nm) with a mixture of synthetic root exudates (SRE) and its components such as sugars, amino acids, organic acids, and phenolic acids by nano isothermal titration calorimetry. The data revealed a strong binding constant (K d = 5.645 × 10 3 M -1 ) for Cu-NPs SRE interaction, however, the binding of Cu 2+ was found stronger but varied for individual SRE components (Huang et al 2017).…”