Dissolution Of Zinc Oxide Nanoparticles Research Articles

Quantification of ZnO Nanoparticle Uptake, Distribution, and Dissolution within Individual Human Macrophages

The usefulness of zinc oxide (ZnO) nanoparticles has led to their wide distribution in consumer products, despite only a limited understanding of how this nanomaterial behaves within biological systems. From a nanotoxicological viewpoint the interaction(s) of ZnO nanoparticles with cells of the immune system is of specific interest, as these nanostructures are readily phagocytosed. In this study, rapid scanning X-ray fluorescence microscopy was used to assay the number ZnO nanoparticles associated with ∼1000 individual THP-1 monocyte-derived human macrophages. These data showed that nanoparticle-treated cells endured a 400% elevation in total Zn levels, 13-fold greater than the increase observed when incubated in the presence of an equitoxic concentration of ZnCl2. Even after excluding the contribution of internalized nanoparticles, Zn levels in nanoparticle treated cells were raised ∼200% above basal levels. As dissolution of ZnO nanoparticles is critical to their cytotoxic response, we utilized a strategy combining ion beam milling, X-ray fluorescence and scanning electron microscopy to directly probe the distribution and composition of ZnO nanoparticles throughout the cellular interior. This study demonstrated that correlative photon and ion beam imaging techniques can provide both high-resolution and statistically powerful information on the biology of metal oxide nanoparticles at the single-cell level. Our approach promises ready application to broader studies of phenomena at the interface of nanotechnology and biology.

Toxicity and Transcriptomic Analysis in Hyalella azteca Suggests Increased Exposure and Susceptibility of Epibenthic Organisms to Zinc Oxide Nanoparticles

Nanoparticles (NPs) are expected to make their way into the aquatic environment where sedimentation of particles will likely occur, putting benthic organisms at particular risk. Therefore, organisms such as Hyalella azteca, an epibenthic crustacean which forages at the sediment surface, is likely to have a high potential exposure. Here we show that zinc oxide (ZnO) NPs are more toxic to H. azteca compared with the corresponding metal ion, Zn(2+). Dissolution of ZnO NPs contributes about 50% of the Zn measured in the ZnO NP suspensions, and cannot account for the toxicity of these particles to H. azteca. However, gene expression analysis is unable to distinguish between the ZnO NP exposures and zinc sulfate (ZnSO4) exposures at equitoxic concentrations. These results lead us to hypothesize that ZnO NPs provide an enhanced exposure route for Zn(2+) uptake into H. azteca, and possibly other sediment dwelling organisms. Our study supports the prediction that sediment dwelling organisms are highly susceptible to the effects of ZnO NPs and should be considered in the risk assessment of these nanomaterials.

Agglomeration and dissolution of zinc oxide nanoparticles: role of pH, ionic strength and fulvic acid

Environmental context The number of nano-enabled products reaching consumers is growing exponentially, inevitably resulting in their release to the environment. The environmental fate and mobility of nanomaterials will depend on their physicochemical form(s) under natural conditions. For ZnO nanoparticles, determinations of agglomeration and dissolution under environmentally relevant conditions of pH, ionic strength and natural organic matter content will provide insight into the potential environmental risk of these novel products. Abstract The increasing use of engineered nanoparticles (ENPs) in industrial and household applications has led to their release into the environment and increasing concern about their effects. Proper assessment of the ecological risks of ENPs will require data on their bioavailability, persistence and mobility over a broad range of physicochemical conditions, including environmentally relevant pH, ionic strength and concentrations of natural organic matter (NOM). In this study, fluorescence correlation spectroscopy was used to determine the agglomeration of a ZnO ENP (nZnO) with a nominal size of 20nm. Particle dissolution was followed using scanned stripping chronopotentiometry. The effects of Suwannee River fulvic acid (SRFA, 0–60mgL–1) and the roles of pH (4–10) and ionic strength (0.005–0.1M) were carefully evaluated. Agglomeration of the bare nZnO increased for pH values near the zero point of charge, whereas the dissolution of the particles decreased. At any given pH, an increase in ionic strength generally resulted in a less stable colloidal system. The role of SRFA was highly dependent upon its concentration with increased agglomeration observed at low SRFA : nZnO mass ratios and decreased agglomeration observed at higher SRFA : nZnO mass ratios. The results indicated that in natural systems, both nZnO dispersion and dissolution will be important and highly dependent upon the precise conditions of pH and ionic strength.

Dissolution of ZnO Nanoparticles at Circumneutral pH: A Study of Size Effects in the Presence and Absence of Citric Acid

Understanding size-dependent processes, including dissolution, of engineered nanoparticles is essential in addressing the potential environmental and health impacts of these materials as well as their long-term stability. In this study, experimental measurements of size-dependent dissolution of well-characterized zinc oxide (ZnO) nanoparticles with particle diameters in the range of 4 to 130 nm have been measured at circumneutral pH (pH 7.5) and compared. Dissolution was found to be enhanced with smaller ZnO nanoparticles compared to larger-sized particles, even though the nanoparticles were present in solution as aggregates with hydrodynamic diameters on the order of 1-3 μm in size. The presence of citric acid significantly enhanced the extent of ZnO dissolution for all sizes, and the greatest enhancement was observed for the 4 nm particles. Although these results are found to be in qualitative agreement with theoretical predictions, a linearized form of the Kelvin equation to calculate a surface free energy yielded quantities inconsistent with expected values from the literature. Reasons for this inconsistency are discussed and include potential deviations of solubility behavior from classical thermodynamics as a result of a lack of detailed knowledge of surface structure and surface properties, including the presence of different surface crystal facets, and the aggregation state.

Zinc Oxide Nanoparticles Interfere With Zinc Ion Homeostasis to Cause Cytotoxicity

The toxicological effects of zinc oxide nanoparticles (ZnO-NPs) are attracting increasing concern as the field of nanotechnology progresses. Although the literature suggests that toxicity of ZnO-NPs may be related to their dissolution, the mechanism for ZnO-NP perturbation of cytosolic zinc concentration ([Zn(2+)](c)) homeostasis remains obscure. Using FluoZin-3 and RhodZin-3, this study investigated changes in both [Zn(2+)](c) and mitochondrial free Zn(2+) concentration ([Zn(2+)](m)) under conditions of ZnO-NP treatment in vivo and in vitro. In human leukemia Jurkat cells and human lung carcinoma H1355 cells, ZnO-NP treatment resulted in an elevation of both [Zn(2+)](c) and [Zn(2+)](m). In H1355 cells, ZnO-NP treatment induced depolarization of mitochondrial membrane potential, as well as caspase-3 activation and lactic dehydrogenase (LDH) release. In our in vivo experiments, when rats were exposed to ZnO-NPs, higher [Zn(2+)](c) and [Zn(2+)](m) were recorded in both broncho-alveolar lavage (BAL) cells and white blood cells isolated from ZnO-NP-exposed rats, compared with high efficiency particulate air-filter-protected controls LDH levels were also elevated in the BAL of ZnO-NP-exposed rats compared with controls. A mechanical toxicological pathway for ZnO-NP toxicity is suggested by these results: an elevation in [Zn(2+)](c) resulting from ZnO-NP dissolution in the intracellular endosome; cytosolic Zn(2+) sequestration by mitochondria; and elevated [Zn(2+)](m) leading to mitochondrial dysfunction, caspase activation, and cell apoptosis. We conclude that exposure to ZnO-NPs interferes with the homeostasis of [Zn(2+)](c,) and that elevated [Zn(2+)](c) results in cell apoptosis.

Use of a rapid cytotoxicity screening approach to engineer a safer zinc oxide nanoparticle through iron doping.

The establishment of verifiably safe nanotechnology requires the development of assessment tools to identify hazardous nanomaterial properties that could be modified to improve nanomaterial safety. While there is a lot of debate of what constitutes appropriate safety screening methods, one approach is to use the assessment of cellular injury pathways to collect knowledge about hazardous material properties that could lead to harm to humans and the environment. We demonstrate the use of a multiparameter cytotoxicity assay that evaluates toxic oxidative stress to compare the effects of titanium dioxide (TiO(2)), cerium oxide (CeO(2)), and zinc oxide (ZnO) nanoparticles in bronchial epithelial and macrophage cell lines. The nanoparticles were chosen on the basis of their volume of production and likelihood of spread to the environment. Among the materials, dissolution of ZnO nanoparticles and Zn(2+) release were capable of ROS generation and activation of an integrated cytotoxic pathway that includes intracellular calcium flux, mitochondrial depolarization, and plasma membrane leakage. These responses were chosen on the basis of the compatibility of the fluorescent dyes that contemporaneously assess their response characteristics by a semiautomated epifluorescence procedure. Purposeful reduction of ZnO cytotoxicity was achieved by iron doping, which changed the material matrix to slow Zn(2+) release. In summary, we demonstrate the utility of a rapid throughput, integrated biological oxidative stress response pathway to perform hazard ranking of a small batch of metal oxide nanoparticles, in addition to showing how this assay can be used to improve nanosafety by decreasing ZnO dissolution through Fe doping.

Ultrasound-Induced In Situ Formation of Coordination Organogels from Isobutyric Acids and Zinc Oxide Nanoparticles

The discovery of ultrasound-induced in-situ formation of coordination organogels using various isobutyric acids (such as isobutyric acid or 2-methylisobutyric acid or 2-bromoisobutyric acid) and zinc oxide nanoparticles was described. FTIR and XRD results suggest that ultrasound irradiation triggers the quick dissolution of zinc oxide nanoparticles by isobutyric acids, resulting in the in-situ formation of zinc isobutyrate complexes that undergoes fast sonocrystallization into gel fibers. FESEM results clearly demonstrate the formation of well-defined networks of fibers with several micrometers in length, but the average diameter of the fiber ranges from 30 to 65 nm, depending upon the nature of the isobutyric acids used. A combination of single-crystal structure analysis and powder XRD result was used to envisage the molecular packing present in the gel state. This is probably a very rare case of ultrasound-induced organogelation where metal oxide NPs are used as the precursor.