Bioavailability of nanoscale metal oxides TiO(2), CeO(2), and ZnO to fish

addresses: The Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK.types: Journal Article; Research Support, Non-U.S. Gov'tCopyright © 2010 American Chemical Society. Post print version of article deposited. The final published version is available from: http://dx.doi.org/10.1021/es901971aNanoparticles (NPs) are reported to be a potential environmental health hazard. For organisms living in the aquatic environment, there is uncertainty on exposure because of a lack of understanding and data regarding the fate, behavior, and bioavailability of the nanomaterials in the water column. This paper reports on a series of integrative biological and physicochemical studies on the uptake of unmodified commercial nanoscale metal oxides, zinc oxide (ZnO), cerium dioxide (CeO(2)), and titanium dioxide (TiO(2)), from the water and diet to determine their potential ecotoxicological impacts on fish as a function of concentration. Particle characterizations were performed and tissue concentrations were measured by a wide range of analytical methods. Definitive uptake from the water column and localization of TiO(2) NPs in gills was demonstrated for the first time by use of coherent anti-Stokes Raman scattering (CARS) microscopy. Significant uptake of nanomaterials was found only for cerium in the liver of zebrafish exposed via the water and ionic titanium in the gut of trout exposed via the diet. For the aqueous exposures undertaken, formation of large NP aggregates (up to 3 mum) occurred and it is likely that this resulted in limited bioavailability of the unmodified metal oxide NPs in fish

Potential use of engineered nanoparticles in ocean fertilization for large-scale atmospheric carbon dioxide removal

Artificial ocean fertilization (AOF) aims to safely stimulate phytoplankton growth in the ocean and enhance carbon sequestration. AOF carbon sequestration efficiency appears lower than natural ocean fertilization processes due mainly to the low bioavailability of added nutrients, along with low export rates of AOF-produced biomass to the deep ocean. Here we explore the potential application of engineered nanoparticles (ENPs) to overcome these issues. Data from 123 studies show that some ENPs may enhance phytoplankton growth at concentrations below those likely to be toxic in marine ecosystems. ENPs may also increase bloom lifetime, boost phytoplankton aggregation and carbon export, and address secondary limiting factors in AOF. Life-cycle assessment and cost analyses suggest that net CO2 capture is possible for iron, SiO2 and Al2O3 ENPs with costs of 2–5 times that of conventional AOF, whereas boosting AOF efficiency by ENPs should substantially enhance net CO2 capture and reduce these costs. Therefore, ENP-based AOF can be an important component of the mitigation strategy to limit global warming

The impact of immobile zones on the transport and retention of nanoparticles in porous media

Nanoparticle transport and retention within porous media is treated by conceptualizing the porous media as a series of independent collectors (e.g., Colloid Filtration Theory). This conceptualization assumes that flow phenomena near grain-grain contacts, such as immobile zones (areas of low flow), exert a negligible influence on nanoparticle transport and assumes that retention and release of particles depends only on surface chemistry. This study investigated the impact of immobile zones on nanoparticle transport and retention by employing synchrotron X-ray computed microtomography (SXCMT) to examine pore-scale silver nanoparticle distributions during transport through three sand columns: uniform iron oxide, uniform quartz, and well-graded quartz. Extended tailing was observed during the elution phase of all experiments suggesting that hydraulic retention in immobile zones, not detachment from grains, was the source of tailing. A numerical simulation of fluid flow through an SXCMT data set predicted the presence of immobile zones near grain-grain contacts. SXCMT-determined silver nanoparticle concentrations observed that significantly lower nanoparticle concentrations existed near grain-grain contacts throughout the duration of all experiments. In addition, the SXCMT-determined pore-scale concentration gradients were found to be independent of surface chemistry and grain size distribution, suggesting that immobile zones limit the diffusive transport of nanoparticles toward the collectors. These results suggest that the well-known overprediction of nanoparticle retention by traditional CFT may be due to ignoring the influences of grain-grain contacts and immobile zones. As such, accurate prediction of nanoparticle transport requires consideration of immobile zones and their influence on both hydraulic and surface retention

Enrichments of Metals, Including Methylmercury, in Sewage Spills in South Carolina, USA

Exposure to microbial pathogens is the primary concern of sanitary sewer overflows; however, sewage spills may also be a significant source of toxic metals, including methylmercury (MeHg). Between November 2015 and January 2017, after Hurricane Joaquin, surface water samples were collected routinely from three creeks in Columbia, SC. Routine sampling coincided with six sewage spills. Total mercury (THg) and MeHg (unfiltered and filtered) and 32 other metals (filtered) were measured. Compared with surface water samples, THg (unfiltered and filtered), MeHg (unfiltered), and 19 other metals were significantly higher in sewage spills (all log(10)-transformed) (two-tailed t test, p < 0.05 for all, n = 38-42). Toxic weighting factors were applied to 18 metals, including THg and MeHg, in samples collected directly from sewage spills (n = 3-4) and a wastewater outfall (n = 5). On average, sewage was 18.2 and 12.0 times more toxic for THg and MeHg, respectively, and 1.75 times more toxic for all 18 metals, compared to treated effluent from the wastewater outfall. Results suggest sewage spills were a source of inorganic Hg, MeHg, and other metals to the receiving waters and may potentially contribute to water quality impairments

An Efficient Targeted Drug Delivery through Apotransferrin Loaded Nanoparticles

BACKGROUND: Cancerous state is a highly stimulated environment of metabolically active cells. The cells under these conditions over express selective receptors for assimilation of factors essential for growth and transformation. Such receptors would serve as potential targets for the specific ligand mediated transport of pharmaceutically active molecules. The present study demonstrates the specificity and efficacy of protein nanoparticle of apotransferrin for targeted delivery of doxorubicin. METHODOLOGY/PRINCIPAL FINDINGS: Apotransferrin nanoparticles were developed by sol-oil chemistry. A comparative analysis of efficiency of drug delivery in conjugated and non-conjugated forms of doxorubicin to apotransferrin nanoparticle is presented. The spherical shaped apotransferrin nanoparticles (nano) have diameters of 25-50 etam, which increase to 60-80 etam upon direct loading of drug (direct-nano), and showed further increase in dimension (75-95 etam) in conjugated nanoparticles (conj-nano). The competitive experiments with the transferrin receptor specific antibody showed the entry of both conj-nano and direct-nano into the cells through transferrin receptor mediated endocytosis. Results of various studies conducted clearly establish the superiority of the direct-nano over conj-nano viz. (a) localization studies showed complete release of drug very early, even as early as 30 min after treatment, with the drug localizing in the target organelle (nucleus) (b) pharmacokinetic studies showed enhanced drug concentrations, in circulation with sustainable half-life (c) the studies also demonstrated efficient drug delivery, and an enhanced inhibition of proliferation in cancer cells. Tissue distribution analysis showed intravenous administration of direct nano lead to higher drug localization in liver, and blood as compared to relatively lesser localization in heart, kidney and spleen. Experiments using rat cancer model confirmed the efficacy of the formulation in regression of hepatocellular carcinoma with negligible toxicity to kidney and liver. CONCLUSIONS: The present study thus demonstrates that the direct-nano is highly efficacious in delivery of drug in a target specific manner with lower toxicity to heart, liver and kidney

A 12,800-year-old layer with cometary dust, microspherules, and platinum anomaly recorded in multiple cores from Baffin Bay

The Younger Dryas Impact Hypothesis (YDIH) posits that ~12,800 years ago Earth encountered the debris stream of a disintegrating comet, triggering hemisphere-wide airbursts, atmospheric dust loading, and the deposition of a distinctive suite of extraterrestrial (ET) impact proxies at the Younger Dryas Boundary (YDB). Until now, evidence supporting this hypothesis has come only from terrestrial sediment and ice-core records. Here we report the first discovery of similar impact-related proxies in ocean sediments from four marine cores in Baffin Bay that span the YDB layer at water depths of 0.5–2.4 km, minimizing the potential for modern contamination. Using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and laser ablation ICP-MS, we detect synchronous abundance peaks of metallic debris geochemically consistent with cometary dust, co-occurring with iron- and silica-rich microspherules (4–163 μm) that are predominantly of terrestrial origin with minor (<2 wt%) ET contributions. These microspherules were likely formed by low-altitude touchdown airbursts and surface impacts of comet fragments and were widely dispersed. In addition, single-particle ICP-TOF-MS analysis reveals nanoparticles (<1 μm) enriched in platinum, iridium, nickel, and cobalt. Similar platinum-group element anomalies at the YDB have been documented at dozens of sites worldwide, strongly suggesting an ET source. Collectively, these findings provide robust support for the YDIH. The impact event likely triggered massive meltwater flooding, iceberg calving, and a temporary shutdown of thermohaline circulation, contributing to abrupt Younger Dryas cooling. Our identification of a YDB impact layer in deep marine sediments underscores the potential of oceanic records to broaden our understanding of this catastrophic event and its climatological impacts