Surface interactions with compartmentalized cellular phosphates explain rare earth oxide nanoparticle hazard and provide opportunities for safer design

A decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping)

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) 'Nano Task Force' proposes a Decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping) that consists of 3 tiers to assign nanomaterials to 4 main groups, to perform sub-grouping within the main groups and to determine and refine specific information needs. The DF4nanoGrouping covers all relevant aspects of a nanomaterial's life cycle and biological pathways, i.e. intrinsic material and system-dependent properties, biopersistence, uptake and biodistribution, cellular and apical toxic effects. Use (including manufacture), release and route of exposure are applied as 'qualifiers' within the DF4nanoGrouping to determine if, e.g. nanomaterials cannot be released from a product matrix, which may justify the waiving of testing. The four main groups encompass (1) soluble nanomaterials, (2) biopersistent high aspect ratio nanomaterials, (3) passive nanomaterials, and (4) active nanomaterials. The DF4nanoGrouping aims to group nanomaterials by their specific mode-of-action that results in an apical toxic effect. This is eventually directed by a nanomaterial's intrinsic properties. However, since the exact correlation of intrinsic material properties and apical toxic effect is not yet established, the DF4nanoGrouping uses the 'functionality' of nanomaterials for grouping rather than relying on intrinsic material properties alone. Such functionalities include system-dependent material properties (such as dissolution rate in biologically relevant media), bio-physical interactions, in vitro effects and release and exposure. The DF4nanoGrouping is a hazard and risk assessment tool that applies modern toxicology and contributes to the sustainable development of nanotechnological products. It ensures that no studies are performed that do not provide crucial data and therefore saves animals and resources.

Enhancing the imaging and biosafety of upconversion nanoparticles through phosphonate coating

Upconversion nanoparticles (UCNPs), which are generated by doping with rare earth (RE) metals, are increasingly used for bioimaging because of the advantages they hold over conventional fluorophores. However, because pristine RE nanoparticles (NPs) are unstable in acidic physiological fluids (e.g., lysosomes), leading to intracellular phosphate complexation with the possibility of lysosomal injury, it is important to ensure that UCNPs are safely designed. In this study, we used commercially available NaYF4:Er/Yb UCNPs to study their stability in lysosomes and simulated lysosomal fluid. We demonstrate that phosphate complexation leads to REPO4 deposition on the particle surfaces and morphological transformation. This leads to a decline in upconversion fluorescence efficiency as well as inducing pro-inflammatory effects at the cellular level and in the intact lung. In order to preserve the imaging properties of the UCNPs as well as improve their safety, we experimented with a series of phosphonate chemical moieties to passivate particle surfaces through the strong coordination of the organophosphates with RE atoms. Particle screening and physicochemical characterization revealed that ethylenediamine tetra(methylenephosphonic acid) (EDTMP) surface coating provides the most stable UCNPs, which maintain their imaging intensity and do not induce pro-inflammatory effects in vitro and in vivo. In summary, phosphonate coating presents a safer design method that preserves and improves the bioimaging properties of UCNPs, thereby enhancing their biological use.

PEGylated Gd(OH)3 nanorods as metabolizable contrast agents for computed tomography imaging

PEGylated Gd(OH)₃ nanorods have been efficiently prepared via a facile and green hydrothermal route and used as a metabolizable computed tomography contrast agent for in vivo imaging.

Quantifying the total ionic release from nanoparticles after particle-cell contact

In order to assess the potential hazards of nanoparticles (NPs) releasing, better knowledge about their toxicity to microbes is required. However, it remains controversial whether NPs could exert particles pecifictoxicity. In this study, the toxic impacts of four kinds of rare earth oxides (REO) NPs (La(2)O(3),CeO(2), Gd(2)O(3), and Yb(2)O(3)) on gram-negative Escherichia coli (E. coli) pBR322 were examined. The results indicate that all the tested NPs possessed cytotoxicity against E. coli. To evaluate the ion-related toxicity of REO NPs, the NPs dissolution in the presence of test organisms was quantitatively measured using X-ray absorption fine structure (XAFS) spectroscopy. Our results suggest that NPs-cell contact could facilitate the dissolution of NPs, and the additional ionic release at the particle-cell interface might result in a substantial increase in the ion-related toxicities towards the test organisms. Therefore, the ion-related toxicity of NPs might be grossly underestimated if the additional dissolution of NPs caused by particle-cell contact was overlooked, further leading to a false interpretation of particle-specific toxicity. To the best of our knowledge, this is the first determination of the total NPs dissolution after particle-cell contact. These findings are helpful to advance mechanistic understanding of the toxicity exerted by dissolvable metal-based NPs.

Fortification and health: challenges and opportunities

Fortification is the process of adding nutrients or non-nutrient bioactive components to edible products (e.g., food, food constituents, or supplements). Fortification can be used to correct or prevent widespread nutrient intake shortfalls and associated deficiencies, to balance the total nutrient profile of a diet, to restore nutrients lost in processing, or to appeal to consumers looking to supplement their diet. Food fortification could be considered as a public health strategy to enhance nutrient intakes of a population. Over the past century, fortification has been effective at reducing the risk of nutrient deficiency diseases such as beriberi, goiter, pellagra, and rickets. However, the world today is very different from when fortification emerged in the 1920s. Although early fortification programs were designed to eliminate deficiency diseases, current fortification programs are based on low dietary intakes rather than a diagnosable condition. Moving forward, we must be diligent in our approach to achieving effective and responsible fortification practices and policies, including responsible marketing of fortified products. Fortification must be applied prudently, its effects monitored diligently, and the public informed effectively about its benefits through consumer education efforts. Clear lines of authority for establishing fortification guidelines should be developed and should take into account changing population demographics, changes in the food supply, and advances in technology. This article is a summary of a symposium presented at the ASN Scientific Sessions and Annual Meeting at Experimental Biology 2014 on current issues involving fortification focusing primarily on the United States and Canada and recommendations for the development of responsible fortification practices to ensure their safety and effectiveness.

The nanoparticle biomolecule corona: lessons learned – challenge accepted?

Besides the wide use of engineered nanomaterials (NMs) in technical products, their applications are not only increasing in biotechnology and biomedicine, but also in the environmental field.

Upconverting nanoparticles: assessing the toxicity

Based on a survey of existing studies, low nanotoxicity of lanthanide doped upconverting nanoparticles holds promise for their safety and suitability for biomedical detection and imaging.

In vivo detection of magnetic labeled oxidized multi-walled carbon nanotubes by magnetic resonance imaging

Functionalized carbon nanotubes (f-CNTs) have been widely used in bio-medicine as drug carriers, bio-sensors, imaging agents and tissue engineering additives, which demands better understanding of their in vivo behavior because of the increasing exposure potential to humans. However, there are limited studies to investigate the in vivo biodistribution and elimination of f-CNTs. In this study, superparamagnetic iron oxides (SPIOs) were used to label oxidized multiwalled carbon nanotubes (o-MWCNTs) for in vivo distribution study of o-MWCNTs by magnetic resonance imaging (MRI). SPIO labeled o-MWCNTs (((SPIO))o-MWCNTs) were prepared by a hydrothermal reaction process, and characterized by TEM, XRD and magnetometer. ((SPIO))o-MWCNTs exhibited superparamagnetic property, excellent biocompatibility and stability. The intravenously injected ((SPIO))o-MWCNTs were observed in liver, kidney and spleen, while the subcutaneously injected ((SPIO))o-MWCNTs could be only detected in sub mucosa. Most of the intravenously injected ((SPIO))o-MWCNTs could be eliminated from liver, spleen, kidney and sub mucosa on 4 d post injection (P.I.). However, the residual o-MWCNTs could induce 30-40% MRI signal-to-noise ratio changes in these tissues even on 30 d P.I. This in vivo biodistribution and elimination information of o-MWCNTs will greatly facilitate the application of f-CNT based nanoproducts in biomedicine. In addition, the magnetic labeling method provides an approach to investigate the in vivo biodistribution and clearance of other nanomaterials.

Interference in autophagosome fusion by rare earth nanoparticles disrupts autophagic flux and regulation of an interleukin-1β producing inflammasome

Engineered nanomaterials (ENMs) including multiwall carbon nanotubes (MWCNTs) and rare earth oxide (REO) nanoparticles, which are capable of activating the NLRP3 inflammasome and inducing IL-1β production, have the potential to cause chronic lung toxicity. Although it is known that lysosome damage is an upstream trigger in initiating this pro-inflammatory response, the same organelle is also an important homeostatic regulator of activated NLRP3 inflammasome complexes, which are engulfed by autophagosomes and then destroyed in lysosomes after fusion. Although a number of ENMs have been shown to induce autophagy, no definitive research has been done on the homeostatic regulation of the NLRP3 inflammasome during autophagic flux. We used a myeloid cell line (THP-1) and bone marrow derived macrophages (BMDM) to compare the role of autophagy in regulating inflammasome activation and IL-1β production by MWCNTs and REO nanoparticles. THP-1 cells express a constitutively active autophagy pathway and are also known to mimic NLRP3 activation in pulmonary macrophages. We demonstrate that, while activated NLRP3 complexes could be effectively removed by autophagosome fusion in cells exposed to MWCNTs, REO nanoparticles interfered in autophagosome fusion with lysosomes. This leads to the accumulation of the REO-activated inflammasomes, resulting in robust and sustained IL-1β production. The mechanism of REO nanoparticle interference in autophagic flux was clarified by showing that they disrupt lysosomal phosphoprotein function and interfere in the acidification that is necessary for lysosome fusion with autophagosomes. Binding of LaPO4 to the REO nanoparticle surfaces leads to urchin-shaped nanoparticles collecting in the lysosomes. All considered, these data demonstrate that in contradistinction to autophagy induction by some ENMs, specific materials such as REOs interfere in autophagic flux, thereby disrupting homeostatic regulation of activated NLRP3 complexes.

Aspect ratio plays a role in the hazard potential of CeO2 nanoparticles in mouse lung and zebrafish gastrointestinal tract

We have previously demonstrated that there is a relationship between the aspect ratio (AR) of CeO2 nanoparticles and in vitro hazard potential. CeO2 nanorods with AR ≥ 22 induced lysosomal damage and progressive effects on IL-1β production and cytotoxicity in the human myeloid cell line, THP-1. In order to determine whether this toxicological paradigm for long aspect ratio (LAR) CeO2 is also relevant in vivo, we performed comparative studies in the mouse lung and gastrointestinal tract (GIT) of zebrafish larvae. Although oropharyngeal aspiration could induce acute lung inflammation for CeO2 nanospheres and nanorods, only the nanorods with the highest AR (C5) induced significant IL-1β and TGF-β1 production in the bronchoalveolar lavage fluid at 21 days but did not induce pulmonary fibrosis. However, after a longer duration (44 days) exposure to 4 mg/kg of the C5 nanorods, more collagen production was seen with CeO2 nanorods vs nanospheres after correcting for Ce lung burden. Using an oral-exposure model in zebrafish larvae, we demonstrated that C5 nanorods also induced significant growth inhibition, a decrease in body weight, and delayed vertebral calcification. In contrast, CeO2 nanospheres and shorter nanorods had no effect. Histological and transmission electron microscopy analyses showed that the key injury mechanism of C5 was in the epithelial lining of the GIT, which demonstrated blunted microvilli and compromised digestive function. All considered, these data demonstrate that, similar to cellular studies, LAR CeO2 nanorods exhibit more toxicity in the lung and GIT, which could be relevant to inhalation and environmental hazard potential.

Nanotechnology in agri-food production: an overview

Nanotechnology is one of the most important tools in modern agriculture, and agri-food nanotechnology is anticipated to become a driving economic force in the near future. Agri-food themes focus on sustainability and protection of agriculturally produced foods, including crops for human consumption and animal feeding. Nanotechnology provides new agrochemical agents and new delivery mechanisms to improve crop productivity, and it promises to reduce pesticide use. Nanotechnology can boost agricultural production, and its applications include: 1) nanoformulations of agrochemicals for applying pesticides and fertilizers for crop improvement; 2) the application of nanosensors/nanobiosensors in crop protection for the identification of diseases and residues of agrochemicals; 3) nanodevices for the genetic manipulation of plants; 4) plant disease diagnostics; 5) animal health, animal breeding, poultry production; and 6) postharvest management. Precision farming techniques could be used to further improve crop yields but not damage soil and water, reduce nitrogen loss due to leaching and emissions, as well as enhance nutrients long-term incorporation by soil microorganisms. Nanotechnology uses include nanoparticle-mediated gene or DNA transfer in plants for the development of insect-resistant varieties, food processing and storage, nanofeed additives, and increased product shelf life. Nanotechnology promises to accelerate the development of biomass-to-fuels production technologies. Experts feel that the potential benefits of nanotechnology for agriculture, food, fisheries, and aquaculture need to be balanced against concerns for the soil, water, and environment and the occupational health of workers. Raising awareness of nanotechnology in the agri-food sector, including feed and food ingredients, intelligent packaging and quick-detection systems, is one of the keys to influencing consumer acceptance. On the basis of only a handful of toxicological studies, concerns have arisen regarding the safety of nanomaterials, and researchers and companies will need to prove that these nanotechnologies do not have more of a negative impact on the environment.