The toxicity and potential pathogenicity of high-performance engineered multi-walled carbon nanotubes

The potential health consequences of carbon nanotube (CNT) exposure is often compared to asbestos and other fibre like materials due to their similar high aspect ratio and potential biopersistence; both are key in driving fibre toxicity and pathogenicity. With similar characteristics CNT are hypothesised to induce similar toxicity, and potentially similar pathogenicity. It is important to test this hypothesis in order to inform safe methods for production, handling and disposal of CNT. The aim for this research was to employ a range of biological techniques to ascertain the cytotoxicity of different multi-walled (MW)CNT that are morphologically and compositionally distinct, and comparing these samples to toxicologically relevant materials such as asbestos and carbon black nanoparticles. The MWCNT used were either supplied by an industrial source, or were produced using controlled growth methods to allow investigation into certain size ranges, catalytic iron content, and sample purity (crystallinity). Using cell free, in vitro and in vivo techniques for oxidative stress assessment, an early generation of ROS was found in response to entangled MWCNT, with greater observed responses to both short and long, straight MWCNT found as exposure times progressed. Also most prominent at the later exposure periods, substantial and significant cell death was observed in MM6 and J774A.1 cells in response to MWCNT samples, measured through reduced cellular viability and LDH release. The level of cell death induced by MWCNT was not matched by cell exposures to reference materials. Numerous markers of a pro-inflammatory responses and markers indicative of tissue damage and angiogenesis were assessed in vitro using MM6 and J774.A1 cell. Both cell types were found to secrete significantly elevated levels of MCP-1, TNF-α, TGF-β and VEGF in response to MWCNT. Although not as high as the CNT, LFA was also found to stimulate pronounced pro-inflammatory conditions, when compared to the other reference materials. Numerous techniques were employed to assess the ability of immortalised and primary cells to phagocytose particles. Frustrated phagocytosis was observed in response to the longer particles (both CNT and asbestos) and to agglomerates formed of shorter CNT. This frustrated phagocytosis induced by the long MWCNT samples was found to translate to an exaggerated respiratory burst, and a dysfunction and inhibition in the ability of cells to phagocytose fluorescently labelled E. coli. Taking all of the results of this study into consideration it was clear that the MWCNT samples tested display a greater toxicity than the reference materials in this panel. Above all, differences in the responses to the five MWCNT samples were considered to be induced by either a long individual length, or large agglomerate formation, and therefore the effects attributed to a high aspect ratio and frustrated phagocytosis. However, at times there was an inference that a high bioavailable iron content or high level of sample purity may intensify cellular response to MWCNT. The findings here, and throughout the current literature, demonstrate that CNT are certainly capable of inducing pathogenesis, but biological responses vary with differences in CNT morphology and composition.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The toxicity and potential pathogenicity of high-performance engineered multi-walled carbon nanotubes.

The potential health consequences of carbon nanotube (CNT) exposure is often compared to asbestos and other fibre like materials due to their similar high aspect ratio and potential biopersistence; both are key in driving fibre toxicity and pathogenicity. With similar characteristics CNT are hypothesised to induce similar toxicity, and potentially similar pathogenicity. It is important to test this hypothesis in order to inform safe methods for production, handling and disposal of CNT.The aim for this research was to employ a range of biological techniques to ascertain the cytotoxicity of different multi-walled (MW)CNT that are morphologically and compositionally distinct, and comparing these samples to toxicologically relevant materials such as asbestos and carbon black nanoparticles. The MWCNT used were either supplied by an industrial source, or were produced using controlled growth methods to allow investigation into certain size ranges, catalytic iron content, and sample purity (crystallinity). Using cell free, in vitro and in vivo techniques for oxidative stress assessment, an early generation of ROS was found in response to entangled MWCNT, with greater observed responses to both short and long, straight MWCNT found as exposure times progressed. Also most prominent at the later exposure periods, substantial and significant cell death was observed in MM6 and J774A.1 cells in response to MWCNT samples, measured through reduced cellular viability and LDH release. The level of cell death induced by MWCNT was not matched by cell exposures to reference materials. Numerous markers of a pro-inflammatory responses and markers indicative of tissue damage and angiogenesis were assessed in vitro using MM6 and J774.A1 cell. Both cell types were found to secrete significantly elevated levels of MCP-1, TNF-?, TGF-? and VEGF in response to MWCNT. Although not as high as the CNT, LFA was also found to stimulate pronounced pro-inflammatory conditions, when compared to the other reference materials. Numerous techniques were employed to assess the ability of immortalised and primary cells to phagocytose particles. Frustrated phagocytosis was observed in response to the longer particles (both CNT and asbestos) and to agglomerates formed of shorter CNT. This frustrated phagocytosis induced by the long MWCNT samples was found to translate to an exaggerated respiratory burst, and a dysfunction and inhibition in the ability of cells to phagocytose fluorescently labelled E. coli.Taking all of the results of this study into consideration it was clear that the MWCNT samples tested display a greater toxicity than the reference materials in this panel. Above all, differences in the responses to the five MWCNT samples were considered to be induced by either a long individual length, or large agglomerate formation, and therefore the effects attributed to a high aspect ratio and frustrated phagocytosis. However, at times there was an inference that a high bioavailable iron content or high level of sample purity may intensify cellular response to MWCNT. The findings here, and throughout the current literature, demonstrate that CNT are certainly capable of inducing pathogenesis, but biological responses vary with differences in CNT morphology and composition

A network-based analysis of critical resource accessibility during floods

Numerous government and non-governmental agencies are increasing their efforts to better quantify the disproportionate effects of climate risk on vulnerable populations with the goal of creating more resilient communities. Sociodemographic based indices have been the primary source of vulnerability information the past few decades. However, using these indices fails to capture other facets of vulnerability, such as the ability to access critical resources (e.g., grocery stores, hospitals, pharmacies, etc.). Furthermore, methods to estimate resource accessibility as storms occur (i.e., in near-real time) are not readily available to local stakeholders. We address this gap by creating a model built on strictly open-source data to solve the user equilibrium traffic assignment problem to calculate how an individual's access to critical resources changes during and immediately after a flood event. Redundancy, reliability, and recoverability metrics at the household and network scales reveal the inequitable distribution of the flood's impact. In our case-study for Austin, Texas we found that the most vulnerable households are the least resilient to the impacts of floods and experience the most volatile shifts in metric values. Concurrently, the least vulnerable quarter of the population often carries the smallest burdens. We show that small and moderate inequalities become large inequities when accounting for more vulnerable communities' lower ability to cope with the loss of accessibility, with the most vulnerable quarter of the population carrying four times as much of the burden as the least vulnerable quarter. The near-real time and open-source model we developed can benefit emergency planning stakeholders by helping identify households that require specific resources during and immediately after hazard events

A method to assess the relevance of nanomaterial dissolution during reactivity testing

The reactivity of particle surfaces can be used as a criterion to group nanoforms (NFs) based on similar potential hazard. Since NFs may partially or completely dissolve over the duration of the assays, with the ions themselves inducing a response, reactivity assays commonly measure the additive reactivity of the particles and ions combined. Here, we determine the concentration of ions released over the course of particle testing, and determine the relative contributions of the released ions to the total reactivity measured. We differentiate three classes of reactivity, defined as being A) dominated by particles, B) additive of particles and ions, or C) dominated by ions. We provide examples for each class by analyzing the NF reactivity of Fe2O3, ZnO, CuO, Ag using the ferric reduction ability of serum (FRAS) assay. Furthermore, another two reactivity tests were performed: Dichlorodihydrofluorescin diacetate (DCFH2‑DA) assay and electron paramagnetic resonance (EPR) spectroscopy. We compare assays and demonstrate that the dose‑response may be almost entirely assigned to ions in one assay (CuO in DCFH2‑DA), but to particles in others (CuO in EPR and FRAS). When considering this data, we conclude that one cannot specify the contribution of ions to NF toxicity for a certain NF, but only for a certain NF in a specific assay, medium and dose. The extent of dissolution depends on the buffer used, particle concentration applied, and duration of exposure. This culminates in the DCFH2‑DA, EPR, FRAS assays being performed under different ion‑to‑particle ratios, and differing in their sensitivity towards reactions induced by either ions or particles. If applied for grouping, read‑across, or other concepts based on the similarity of partially soluble NFs, results on reactivity should only be compared if measured by the same assay, incubation time, and dose range

2012 Annual Report - Advanced Biomedical Information Technology Core

This material is based upon work supported in part by the following funding agencies and grant awards: • Lilly Endowment, for its support of the Indiana Genomics Initiative (INGEN) – 2000; Indiana Metabolomics and Cytomics Initiative (METACyt); Indiana Pervasive Computing Research (IPCRES) initiative and Pervasive Technology Institute (1999 and 2008 respectively) • National Science Foundation under grants 01116050 MRI: Creation of the AVIDD Data Facility: A Distributed Facility for Managing, Analyzing and Visualizing Instrument-Driven Data (Michael A. McRobbie, PI); 0521433 MRI: Acquisition of a High-Speed, High Capacity Storage System to Support Scientific Computing: The Data Capacitor (Craig A. Stewart, PI); 0521433 ABI Development: National Center for Genome Analysis Support (Craig A. Stewart, PI) • National Institutes of Health NIAAA awards U24 AA014818-01 (Craig A. Stewart, PI) and U24 AA014818-04 (William K. Barnett, PI) Informatics Core for the Collaborative Initiative on Fetal Alcohol Spectrum Disorder • Subcontracts through the following NIH grant awards: 5P40RR024928 (Kenneth Cornetta, PI), 2U01AA014809 (Tatiana Foroud, PI), 1DP2OD007363-01 (Alexander Niculescu, PI), UL1RR025761-01 (Anantha Shekhar, PI), 3UL1RR025761-04S2 (Anantha Shekhar, PI), and 3UL1RR025761-04S3 (Anantha Shekhar, PI) • Funding from the general funds of Indiana University Any opinions expressed in this document are those of the authors and do not necessarily reflect the views of the funding agencies above

The oxidative potential of differently charged silver and gold nanoparticles on three human lung epithelial cell types

BACKGROUND: Nanoparticle (NPs) functionalization has been shown to affect their cellular toxicity. To study this, differently functionalized silver (Ag) and gold (Au) NPs were synthesised, characterised and tested using lung epithelial cell systems. METHODS: Monodispersed Ag and Au NPs with a size range of 7 to 10 nm were coated with either sodium citrate or chitosan resulting in surface charges from -50 mV to +70 mV. NP-induced cytotoxicity and oxidative stress were determined using A549 cells, BEAS-2B cells and primary lung epithelial cells (NHBE cells). TEER measurements and immunofluorescence staining of tight junctions were performed to test the growth characteristics of the cells. Cytotoxicity was measured by means of the CellTiter-Blue ® and the lactate dehydrogenase assay and cellular and cell-free reactive oxygen species (ROS) production was measured using the DCFH-DA assay. RESULTS: Different growth characteristics were shown in the three cell types used. A549 cells grew into a confluent mono-layer, BEAS-2B cells grew into a multilayer and NHBE cells did not form a confluent layer. A549 cells were least susceptible towards NPs, irrespective of the NP functionalization. Cytotoxicity in BEAS-2B cells increased when exposed to high positive charged (+65-75 mV) Au NPs. The greatest cytotoxicity was observed in NHBE cells, where both Ag and Au NPs with a charge above +40 mV induced cytotoxicity. ROS production was most prominent in A549 cells where Au NPs (+65-75 mV) induced the highest amount of ROS. In addition, cell-free ROS measurements showed a significant increase in ROS production with an increase in chitosan coating. CONCLUSIONS: Chitosan functionalization of NPs, with resultant high surface charges plays an important role in NP-toxicity. Au NPs, which have been shown to be inert and often non-cytotoxic, can become toxic upon coating with certain charged molecules. Notably, these effects are dependent on the core material of the particle, the cell type used for testing and the growth characteristics of these cell culture model systems

A comparison of dermal toxicity models; assessing suitability for safe(r)-by-design decision-making and for screening nanomaterial hazards

The objective of Safe-by-Design (SbD) is to support the development of safer products and production processes, and enable safe use throughout a materials' life cycle; an intervention at an early stage of innovation can greatly benefit industry by reducing costs associated with the development of products later found to elicit harmful effects. Early hazard screening can support this process, and is needed for all of the expected nanomaterial exposure routes, including inhalation, ingestion and dermal. In this study, we compare in vitro and ex vivo cell models that represent dermal exposures (including HaCaT cells, primary keratinocytes, and reconstructed human epidermis (RhE)), and when possible consider these in the context of regulatory accepted OECD TG for in vitro dermal irritation. Various benchmark nanomaterials were used to assess markers of cell stress in each cell model. In addition, we evaluated different dosing strategies that have been used when applying the OECD TG for dermal irritation in assessment of nanomaterials, and how inconsistencies in the approach used can have considerable impact of the conclusions made. Although we could not demonstrate alignment of all models used, there was an indication that the simpler in vitro cell model aligned more closely with RhE tissue than ex vivo primary keratinocytes, supporting the use of HaCaT cells for screening of dermal toxicity of nanomaterials and in early-stage SbD decision-making

Is the toxic potential of nanosilver dependent on its size?

Background: Nanosilver is one of the most commonly used engineered nanomaterials (ENMs). In our study we focused on assessing the size-dependence of the toxicity of nanosilver (Ag ENMs), utilising materials of three sizes (50, 80 and 200 nm) synthesized by the same method, with the same chemical composition, charge and coating. Methods: Uptake and localisation (by Transmission Electron Microscopy), cell proliferation (Relative growth activity) and cytotoxic effects (Plating efficiency), inflammatory response (induction of IL-8 and MCP-1 by Enzyme linked immune sorbent assay), DNA damage (strand breaks and oxidised DNA lesions by the Comet assay) were all assessed in human lung carcinoma epithelial cells (A549), and the mutagenic potential of ENMs (Mammalian hprt gene mutation test) was assessed in V79-4 cells as per the OECD protocol. Detailed physico-chemical characterization of the ENMs was performed in water and in biological media as a prerequisite to assessment of their impacts on cells. To study the relationship between the surface area of the ENMs and the number of ENMs with the biological response observed, Ag ENMs concentrations were recalculated from g/cm2 to ENMs cm2/cm2 and ENMs/cm2. Results. Studied Ag ENMs are cytotoxic and cytostatic, and induced strand breaks, DNA oxidation, inflammation and gene mutations. Results expressed in mass unit [g/cm2] suggested that the toxicity of Ag ENMs is size dependent with 50 nm being most toxic. However, re-calculation of Ag ENMs concentrations from mass unit to surface area and number of ENMs per cm2 highlighted that 200 nm Ag ENMs, are the most toxic. Results from hprt gene mutation assay showed that Ag ENMs 200 nm are the most mutagenic irrespective of the concentration unit expressed. Conclusion: We found that the toxicity of Ag ENMs is not always size dependent. Strong cytotoxic and genotoxic effects were observed in cells exposed to Ag ENMs 50 nm, but Ag ENMs 200 nm had the most mutagenic potential. Additionally, we showed that expression of concentrations of ENMs in mass units is not representative. Number of ENMs or surface area of ENMs (per cm2) seem more precise units with which to compare the toxicity of different ENMs.(VLID)156960