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1. Copper oxide nanoparticle dissolution at alkaline pH is controlled by dissolved organic matter: influence of soil-derived organic matter, wheat, bacteria, and nanoparticle coating

   https://doi.org/10.1039/d0en00574f  

   Hortin, J. M.; Anderson, A. J.; Britt, D. W.; Jacobson, A. R.; McLean, J. E. (January 2020, Environmental Science: Nano)

   Dissolution of CuO nanoparticles, releasing Cu ions, is a primary mechanism of Cu interaction in the rooting zone of plants. CuO dissolution is sometimes incorrectly considered negligible at high pH, since complexation of Cu with dissolved organic matter may enhance nanoparticle dissolution. Therefore data on the effects of plant-microbial-soil interactions on nanoparticle dissolution, particularly in alkaline soils, are needed. Dissolution of CuO nanoparticles (100 mg kg −1 Cu) was studied in sand supplemented with factorial combinations of wheat growth, a root-colonizing bacterium, and saturated paste extracts (SPEs) from three alkaline, calcareous soils. In control sand systems with 3.34 mM Ca(NO 3 ) 2 solution, dissolved Cu was low (266 μg L −1 Cu). Addition of dissolved organic matter via wheat root metabolites and/or soil SPEs increased dissolved Cu to 795–6250 μg L −1 Cu. Dissolution was correlated with dissolved organic carbon ( R = 0.916, p < 0.0001). Ligands >3 kDa, presumably fulvic acid from the SPEs, complexed Cu driving solubility; the addition of plant exudates further increased solubility 1.5–3.5×. The root-colonizing bacterium decreased dissolved Cu in sand pore waters from planted systems due to metabolism of root exudates. Batch solubility studies (10 mg L −1 Cu) with the soil SPEs and defined solutions containing bicarbonate or fulvic acid confirmed elevated CuO nanoparticle solubility at >7.5 pH. Nanoparticle dissolution was suppressed in batch experiments compared to sand, via nanoparticle organic matter coating or homoconjugation of dissolved organic matter. Alterations of CuO nanoparticles by soil organic matter, plant exudates, and bacteria will affect dissolution and bioavailability of the CuO nanoparticles in alkaline soils. 

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2. Review of Oxidative Dissolution and Sulfidation of Select Nanoparticles in the Environment: Impact on Applications

   https://doi.org/10.1021/acsanm.3c06227  

   O’Keefe, Tana L.; Haynes, Christy L. (April 2024, ACS Applied Nano Materials)

   Nanoparticles (NPs) are increasingly being used in medical, electronic, energy, and agricultural applications due to their unique properties that often arise due to the high surface area-to-volume ratio. However, this characteristic along with the high reactivity of NPs make these materials highly dynamic in environmental settings. Thus, several transformations can take place when these materials enter the environment that determines their transport, toxicity, and fate of them in our environment. These transformations, and more specifically oxidative dissolution and sulfidation, are directly impacted by the characteristics that a NP has in addition to the surrounding environmental conditions. Therefore, this review aims to summarize how NP characteristics (size, coatings, etc.) and other important environmentally relevant conditions (oxic/anoxic waters, natural organic matter, etc.) impact the oxidative dissolution and sulfidation of several metal and metal oxide NPs. The impact of these factors is crucial to understanding and predicting the environmental risks of these materials in a wide range of applications. 

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3. Soil-derived fulvic acid and root exudates, modified by soil bacteria, alter CuO nanoparticle-induced root stunting of wheat via Cu complexation

   https://doi.org/10.1039/c9en00728h  

   Hortin, J. M.; Anderson, A. J.; Britt, D. W.; Jacobson, A. R.; McLean, J. E. (December 2019, Environmental Science: Nano)

   CuO nanoparticles (NPs) are explored as fungicides and fertilizers, and are increasingly likely to be applied to agricultural soils. Consequently, interactions of CuO NPs with soil pore water (SPW) components, plants, and microbes must be understood. These experiments examined whether dissolved natural organic matter (DNOM) from SPW, or root/bacterial exudates, changed wheat ( Triticum aestivum L. v. Deloris) responses to 100 mg kg −1 (Cu/sand) as CuO NPs. Seedlings were grown in sand with 3.34 mM Ca(NO 3 ) 2 or one of three SPWs, differing in DNOM concentration and composition. At 10 days post-germination, CuO NPs stunted roots by 59% in the 3.34 mM Ca(NO 3 ) 2 and 26–35% in the three SPWs compared to plants grown without NPs. Malate, citrate, gluconate, and 2′-deoxymugineic acid (DMA), were elevated 1.3 to 5-fold in the rhizosphere with CuO NPs present. Cu was bioavailable through metallo-organic complexes, including Cu–DMA and Cu–gluconate. Fulvic acid in SPWs mitigated CuO NP-induced wheat root shortening. Pseudomonas chlororaphis O6 eliminated malate and citrate in the rhizospheres, reduced rhizosphere dissolved Cu ∼18–66%, and reduced root Cu 39% across all SPWs while enhancing root stunting ∼17% more across all SPWs than non-inoculated wheat grown with CuO NPs. Thus, both SPW components and root microbial colonization influenced wheat responses to CuO NPs. These interactions are likely in agricultural soils with additional processes, such as ion sorption, to influence CuO NP phytotoxicity, highlighting the importance of considering not just the target plant, but soil properties and associated microbiomes when evaluating impacts of NPs in agricultural usage. 

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4. Biomolecular corona formation on CuO nanoparticles in plant xylem fluid

   https://doi.org/10.1039/D1EN00140J  

   Borgatta, Jaya R.; Lochbaum, Christian A.; Elmer, Wade H.; White, Jason C.; Pedersen, Joel A.; Hamers, Robert J. (January 2021, Environmental Science: Nano)

   null (Ed.)

   Biomolecular coatings (coronas) that form on nanomaterials have been widely investigated in animal and bacterial cell culture and in the extracellular and intracellular fluids of animals. Such coronas influence the distribution of nanoparticles within organisms, their uptake by cells, and their storage in intracellular compartments. Plants can be exposed to nanoparticles via either intentional application of nanomaterials in agriculture or inadvertently due, for example, to biosolids amendment of soils. Development of a mechanistic understanding of nanoparticle transport and fate within plants requires consideration of corona acquisition within plants, particularly within the vascular fluids that transport nanoparticles throughout plants. Here, we examine the interactions between copper oxide (CuO) nanoparticles and pumpkin xylem fluid to understand corona formation in an important part of the plant vasculature system. We used CuO nanoparticles because they have emerged as a promising micronutrient source for the suppression of fungal diseases. The corona was composed primarily of proteins, despite the higher abundance of carbohydrates in xylem fluid. We used X-ray photoelectron spectroscopy to determine the thickness of the protein corona. Polyacrylamide gel electrophoresis revealed that protein binding to the CuO nanoparticle surface was selective; the most abundant proteins in the corona were not the most abundant ones in the xylem fluid. We used in situ attenuated total reflectance Fourier-transform infrared spectroscopy to show that the protein–CuO NP interactions were quasi-irreversible, while carbohydrate–CuO interactions were reversible. Corona formation is expected to influence the distribution and transformation of nanomaterials in plants. 

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5. Comparative Molecular Immunological Activity of Physiological Metal Oxide Nanoparticle and its Anticancer Peptide and RNA Complexes

   https://doi.org/10.3390/nano9121670  

   DeLong, Robert K.; Comer, Jeffrey; Mathew, Elza Neelima; Jaberi-Douraki, Majid (December 2019, Nanomaterials)

   null (Ed.)

   Currently, there is a great interest in nanoparticle-based vaccine delivery. Recent studies suggest that nanoparticles when introduced into the biological milieu are not simply passive carriers but may also contribute immunological activity themselves or of their own accord. For example there is considerable interest in the biomedical applications of one of the physiologically-based inorganic metal oxide nanoparticle, zinc oxide (ZnO). Indeed zinc oxide (ZnO) NP are now recognized as a nanoscale chemotherapeutic or anticancer nanoparticle (ANP) and several recent reports suggest ZnO NP and/or its complexes with drug and RNA induce a potent antitumor response in immuno-competent mouse models. A variety of cell culture studies have shown that ZnO NP can induce cytokines such as IFN-γ, TNF-α, IL-2, and IL-12 which are known to regulate the tumor microenvironment. Much less work has been done on magnesium oxide (MgO), cobalt oxide (Co3O4), or nickel oxide (NiO); however, despite the fact that these physiologically-based metal oxide NP are reported to functionally load and assemble RNA and protein onto their surface and may thus also be of potential interest as nanovaccine platform. Here we initially compared in vitro immunogenicity of ZnO and Co3O4 NP and their effects on cancer-associated or tolerogenic cytokines. Based on these data we moved ZnO NP forward to testing in the ex vivo splenocyte assay relative to MgO and NiO NP and these data showed significant difference for flow cytometry sorted population for ZnO-NP, relative to NiO and MgO. These data suggesting both molecular and cellular immunogenic activity, a double-stranded anticancer RNA (ACR), polyinosinic:poly cytidylic acid (poly I:C) known to bind ZnO NP; when ZnO-poly I:C was injected into B16F10-BALB/C tumor significantly induced, IL-2 and IL-12 as shown by Cohen’s d test. LL37 is an anticancer peptide (ACP) currently in clinical trials as an intratumoral immuno-therapeutic agent against metastatic melanoma. LL37 is known to bind poly I:C where it is thought to compete for receptor binding on the surface of some immune cells, metastatic melanoma and lung cells. Molecular dynamic simulations revealed association of LL37 onto ZnO NP confirmed by gel shift assay. Thus using the well-characterized model human lung cancer model cell line (BEAS-2B), poly I:C RNA, LL37 peptide, or LL37-poly I:C complexes were loaded onto ZnO NP and delivered to BEAS-2B lung cells, and the effect on the main cancer regulating cytokine, IL-6 determined by ELISA. Surprisingly ZnO-LL37, but not ZnO-poly I:C or the more novel tricomplex (ZnO-LL37-poly I:C) significantly suppressed IL-6 by >98–99%. These data support the further evaluation of physiological metal oxide compositions, so-called physiometacomposite (PMC) materials and their formulation with anticancer peptide (ACP) and/or anticancer RNA (ACR) as a potential new class of immuno-therapeutic against melanoma and potentially lung carcinoma or other cancers. 

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