•Nano-enabled products might reach their end-of-life by thermal decomposition.•Thermal decomposition provides two by-products: released aerosol and residual ash.•Is there any nanofiller release in ...byproducts?•Risk assessment of potential environmental health implications.
Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.
Reliable predictions of the environmental fate and risk of engineered nanomaterials (ENMs) require a better understanding of ENM reactivity in complex, biologically active systems for chronic ...low-concentration exposure scenarios. Here, simulated freshwater wetland mesocosms were dosed with ENMs to assess how their reactivity and seasonal changes in environmental parameters influence ENM fate in aquatic systems. Copper-based ENMs (Kocide), known to dissolve in water, and gold nanoparticles (AuNPs), stable against dissolution in the absence of specific ligands, were added weekly to mesocosm waters for 9 months. Metal accumulation and speciation changes in the different environmental compartments were assessed over time. Copper from Kocide rapidly dissolved likely associating with organic matter in the water column, transported to terrestrial soils and deeper sediment where it became associated with organic or sulfide phases. In contrast, Au accumulated on/in the macrophytes where it oxidized and transferred over time to surficial sediment. A dynamic seasonal accumulation and metal redox cycling were found between the macrophyte and the surficial sediment for AuNPs. These results demonstrate the need for experimental quantification of how the biological and chemical complexity of the environment, combined with their seasonal variations, drive the fate of metastable ENMs.
Colloid generation, stability, and transport are important processes that can significantly influence the fate and transport of nutrients and contaminants in environmental systems. Here, we ...critically review the existing literature on colloids in redox-dynamic environments and summarize the current state of knowledge regarding the mechanisms of colloid generation and the chemical controls over colloidal behavior in such environments. We also identify critical gaps, such as the lack of universally accepted cross-discipline definition and modeling infrastructure that hamper an in-depth understanding of colloid generation, behavior, and transport potential. We propose to go beyond a size-based operational definition of colloids and consider the functional differences between colloids and dissolved species. We argue that to predict colloidal transport in redox-dynamic environments, more empirical data are needed to parametrize and validate models. We propose that colloids are critical components of element budgets in redox-dynamic systems and must urgently be considered in field as well as lab experiments and reactive transport models. We intend to bring further clarity and openness in reporting colloidal measurements and fate to improve consistency. Additionally, we suggest a methodological toolbox for examining impacts of redox dynamics on colloids in field and lab experiments.
Abstract Recent advancements in the field of hyperpolarized13 C magnetic resonance spectroscopy (MRS) have yielded powerful techniques capable of real-time analysis of metabolic pathways. These ...non-invasive methods have increasingly shown application in impacting disease diagnosis and have further been employed in mechanistic studies of disease onset and progression. Our goals were to investigate branched-chain aminotransferase (BCAT) activity in prostate cancer with a novel molecular probe, hyperpolarized 1-13 C-2-ketoisocaproate (1-13 C-KIC), and explore the potential of branched-chain amino acid (BCAA) metabolism to serve as a biomarker. Using traditional spectrophotometric assays, BCAT enzymatic activities were determined in vitro for various sources of prostate cancer (human, transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse and human cell lines). These preliminary studies indicated that low levels of BCAT activity were present in all models of prostate cancer but enzymatic levels are altered significantly in prostate cancer relative to healthy tissue. The MR spectroscopic studies were conducted with two cellular models (PC-3 and DU-145) that exhibited levels of BCAA metabolism comparable to the human disease state. Hyperpolarized 1-13 C-KIC was administered to prostate cancer cell lines, and the conversion of 1-13 C-KIC to the metabolic product, 1-13 C-leucine (1-13 C-Leu), could be monitored via hyperpolarized13 C MRS.
Recent studies have characterized copper-based nanoparticles (CBNPs) as relatively insoluble, raising potential persistence, accumulation, and toxicological concerns about their long-term application ...as agricultural pesticides. The dissolution rates of two CBNPs were measured in natural and artificial waters under both saturated and unsaturated conditions with respect to CuO(s) (total Cu, <1 mg/kg). Kocide 3000, an agricultural pesticide formulation with nanoscale Cu(OH)2 particles, rapidly dissolved with an experimental half-life of <8 h in natural water. Copper oxide nanoparticles were longer-lived, with an experimental half-life of 73 h in natural water. In contrast to prior reports of CuONP dissolution, our results suggest that even in moderately alkaline waters, CuO and Cu(OH)2 NPs may persist as particles for days to weeks under quiescent conditions in a freshwater environment.
Plant nanobiotechnology promises transformative solutions to the most vexing problems threatening global food security, e.g. drought, disease, and soil nutrient deficiencies. However, poor ...understanding of how NP physiochemical properties affect their fate in/on plants and the lack of effective methods to deliver the nanomaterials to where they are needed in a precise plant compartment impedes these technological innovations. This thesis evaluates how three specific NP properties, charge, solubility, and coating, influence plant uptake, metal distribution, and in planta NP transformation, which will provide insight into the design of efficient and safe nano-enabled agrochemicals. The first objective of this work was to evaluate the influence of surface charge on NP uptake by roots, translocation, and distribution in plant tissue. Wheat was hydroponically exposed to CeO2 NPs functionalized with positively-charged, negatively-charged, or neutral dextran coatings. While the positively-charged NPs adhered significantly more to the roots, the negatively-charged NPs translocated to the shoots most efficiently. Whereas Ce from negatively-charged NP exposed plant was found mostly in the leaf veins, Ce was in the nonvascular leaf tissue of the neutral NP exposed plant. These results demonstrate that different CeO2 NP surface charges result in different Ce localization in leaves. The second objective of this thesis was to compare the influence of charge on NP uptake and distribution between different types of plants. Experiments with these particles using two monocotyledons (corn and rice) and two dicotyledons (tomato and lettuce) indicated that while total Ce uptake was plant-species dependent, likely due to differences in transpiration rates, Ce distribution in the leaves was driven by NP surface charge and were generalizable across all four plants. Comparing leaf vasculature, Ce was able to move much further outside of the main vasculature in the dicot plants than monocot plants, likely due to the larger airspace volume in dicot leaves compared to monocot leaves. This work clearly demonstrates that tuning NPs coating charge can achieve plant compartment targeting after root uptake. The third objective of this work was to determine the influence of Cu-based NP 1-h solubility on metal uptake, distribution and speciation over time in wheat. Higher 1-h solubility Cu(OH)2 NPs provided more uptake of Cu after 1 h of exposure, but the lower 1-h solubility materials (CuO and CuS NPs) were more persistent on/in the roots and continued to slowly deliver Cu to plant leaves over 48 h. The initial NP composition significantly influenced the Cu speciation within the plant roots; the Cu in plants exposed to CuS NPs was mostly reduced and/or sulfidized while the Cu in the CuO NP exposed plants was oxidized and bound to organics. This work demonstrates that tuning initial NP speciation can allow for the delivery of different metal species, resulting in controllable delivery rates and bioavailabilities. The fourth objective of this work was to determine how coating can be modified to increase NP adherence to plant leaf structures, specifically pathogen points of entry. Gold nanoparticles were coated with a biomolecule with affinity for a specific chemical moiety found on guard cells to target leaf stomata. After rinsing, NPs with this coating remained strongly adhered to the stomata on the leaf surface. These results demonstrate, for the first time, active, targeted delivery of NPs to a specific site on live plants via foliar application. Overall, this thesis demonstrates that tuning NP physicochemical properties to achieve specific bioavailability, distribution, targeted delivery in plants is possible. These findings provide key information for the design of nano-enabled agrochemicals that are more targeted, more efficient, and less wasteful.
Root uptake and translocation of engineered nanoparticles (NPs) by plants are dependent on both plant species and NP physicochemical properties. To evaluate the influence of NP surface charge and ...differences in root structure and vasculature on cerium distribution and spatial distribution within plants, two monocotyledons (corn and rice) and two dicotyledons (tomato and lettuce) were exposed hydroponically to positively-charged, negatively-charged, and neutral ~4 nm CeO2 NPs. Here, leaves were analyzed using synchrotron-based X-ray fluorescence microscopy to provide lateral Ce spatial distribution. Surface charge mediated CeO2 NP interactions with roots for all plant species. Positively charged CeO2 NPs associated to the roots more than the negatively charged NPs due to electrostatic attraction/repulsion to the negatively charged root surfaces, with the highest association for the tomato, likely due to higher root surface area. The positive NPs remained primarily adhered to the roots untransformed, while the neutral and negative NPs were more efficiently translocated from the roots to shoots. This translocation efficiency was highest for the tomato and lettuce compared to corn and rice. Across all plant species, the positive and neutral treatments resulted in the formation of Ce clusters outside of the main vasculature in the mesophyll, while the negative treatment resulted in Ce primarily in the main vasculature of the leaves. Comparing leaf vasculature, Ce was able to move much further outside of the main vasculature in the dicot plants than monocot plants, likely due to the larger airspace volume in dicot leaves compared to monocot leaves. These results provide valuable insight into the influence of plant structure and NP properties on metal transport and distribution of NPs in plants.
PDF
![Hyperpolarized [1,4- 13 C]-...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0952-3480/small "Hyperpolarized [1,4- 13 C]-diethylsuccinate: a potential DNP substrate for in vivo metabolic imaging")
