Multi walled carbon nano tubes induced hepatotoxicity in Swiss albino mice

In the present study, multi walled carbon nano tubes (MWCNTs) were synthesized using chemical vapour deposition (CVD) technique. Swiss albino mice were orally administered with single dose of 60 and 100 mg/kg body weight of purified and functionalized MWCNTs suspended in water. The mice were autopsied on 7, 14, 21 and 28 days post exposure. Liver was taken out and part of it fixed in Bouin's solution for histopathological examinations. The remaining part was immersed in cold saline, blotted dry, weighed quickly and homogenized in ice cold buffer. The activity of superoxide dismutase (SOD) and catalase (CAT) was immediately measured in the supernatant. The MWCNTs in liver led to pathological changes, including injury to macrophages, cellular swelling, unspecific inflammation, spot necrosis and blood coagulation. Estimation of SOD and CAT showed altered levels in the experimental groups as compared to controls. Therefore, MWCNTs from manufactured and combustion sources in the environment can have adverse effects on human health.

Efficacy of simple short-term in vitro assays for predicting the potential of metal oxide nanoparticles to cause pulmonary inflammation

BACKGROUND

There has been concern regarding risks from inhalation exposure to nanoparticles (NPs). The large number of particles requiring testing means that alternative approaches to animal testing are needed.

OBJECTIVES

We set out to determine whether short-term in vitro assays that assess intrinsic oxidative stress potential and membrane-damaging potency of a panel of metal oxide NPs can be used to predict their inflammogenic potency.

METHODS

For a panel of metal oxide NPs, we investigated intrinsic free radical generation, oxidative activity in an extracellular environment, cytotoxicity to lung epithelial cells, hemolysis, and inflammation potency in rat lungs. All exposures were carried out at equal surface area doses.

RESULTS

Only nickel oxide (NiO) and alumina 2 caused significant lung inflammation when instilled into rat lungs at equal surface area, suggesting that these two had extra surface reactivity. We observed significant free radical generation with 4 of 13 metal oxides, only one of which was inflammogenic. Only 3 of 13 were significantly hemolytic, two of which were inflammogenic.

CONCLUSIONS

Potency in generating free radicals in vitro did not predict inflammation, whereas alumina 2 had no free radical activity but was inflammogenic. The hemolysis assay was correct in predicting the proinflammatory potential of 12 of 13 of the particles examined. Using a battery of simple in vitro tests, it is possible to predict the inflammogenicity of metal oxide NPs, although some false-positive results are likely. More research using a larger panel is needed to confirm the efficacy and generality of this approach for metal oxide NPs.

Mathematical form factor studies on the effect of water on airborne particles morphology using a bi-dimensional TEM image processing

Mathematical morphology is a tool for extracting image components that are useful for representation and description. The technique consists of a set-theoretic method of image analysis providing a quantitative description of geometrical structures. A simple application of mathematical morphology to a bi-dimensional processing of TEM images of airborne particles allows us to distinguish between particles grown and/or transported in atmosphere under dry conditions or in rainy days by a simple comparison of the corresponding image form factors. The form factors range in the 0.385-0.031 interval in the case of particles sampled in rainy days, and in the 0.103-0.006 interval in the case of non-rainy conditions. The same classification criterion was applied to filters collected under dry conditions and plunged in water. The results demonstrate that a morphological change may be artificially induced to the particle structure. The artificially wet particles, indeed, display an apparent contraction of their structures evidenced by a two-fold increase of the average values of their form factors. The last experiment roughly simulates the impact of particles on membranes of the respiratory tract.

Pulmonary toxicity and environmental contamination: radicals, electron transfer, and protection by antioxidants

The atmosphere is replete with a mixture of toxic substances, both natural and man-made. Inhalation of toxic substances produces a variety of insults to the pulmonary system. Lung poisons include industrial materials, particulates from mining and combustion, agricultural chemicals, cigarette smoke, ozone, and nitrogen oxides, among a large number of other chemicals and environmental contaminants. Many proposals have been advanced to explain the mode of action of pulmonary toxicants. In this review we focus on mechanisms of pulmonary toxicity that involve ET, ROS, and OS. The vast majority of toxicants or their metabolites possess chemical ET functionalities that can undergo redox cycling. Such recycling may generate ROS that can injure various cellular constituents in the lung and in other tissues. ET agents include quinones, metal complexes, aromatic nitro compounds, and conjugated iminium ions. Often, these agents are formed metabolically from parent toxicants. Such metabolic reactions are often catalytic and require only small amounts of the offending material. Oxidative attack is commonly associated with lipid peroxidation and oxidation of DNA, and it may result in strand cleavage and 8-OH-DG production. Toxicity is often accompanied by depletion of natural AOs, which further exacerbates the toxic effect. It is not surprising that the use of AOs, both natural in fruits and vegetables, as well as synthetic, may provide protection from the adverse effects of toxicant exposure. The mechanistic framework described earlier is also applicable to some of the more prominent pulmonary illnesses, such as asthma, COPD, and cancer.

Nanoparticles-a thoracic toxicology perspective

A substantial literature demonstrates that the main ultrafine particles found in ambient urban air are combustion-derived nanoparticles (CDNP) which originate from a number of sources and pose a hazard to the lungs. For CDNP, three properties appear important-surface area, organics and metals. All of these can generate free radicals and so induce oxidative stress and inflammation. Inflammation is a process involved in the diseases exhibited by the individuals susceptible to the effects of PM- development and exacerbations of airways disease and cardiovascular disease. It is therefore possible to implicate CDNP in the common adverse effects of increased PM. The adverse effects of increases in PM on the cardiovascular system are well-documented in the epidemiological literature and, as argued above, these effects are likely to be driven by the combustion-derived NP. The epidemiological findings can be explained in a number of hypotheses regarding the action of NP:-1) Inflammation in the lungs caused by NP causes atheromatous plaque development and destabilization; 2) The inflammation in the lungs causes alteration in the clotting status or fibrinolytic balance favouring thrombogenesis; 3) The NP themselves or metals/organics released by the particles enter the circulation and have direct effects on the endothelium, plaques, the clotting system or the autonomic nervous system/ heart rhythm. Environmental nanoparticles are accidentally produced but they provide a toxicological model for a new class of purposely 'engineered' NP arising from the nanotechnology industry, whose effects are much less understood. Bridging our toxicological knowledge between the environmental nanoparticles and the new engineered nanoparticles is a considerable challenge.

Nanoparticles: health effects--pros and cons

With the advent of nanotechnology, the prospects for using engineered nanomaterials with diameters of < 100 nm in industrial applications, medical imaging, disease diagnoses, drug delivery, cancer treatment, gene therapy, and other areas have progressed rapidly. The potential for nanoparticles (NPs) in these areas is infinite, with novel new applications constantly being explored. The possible toxic health effects of these NPs associated with human exposure are unknown. Many fine particles generally considered "nuisance dusts" are likely to acquire unique surface properties when engineered to nanosize and may exhibit toxic biological effects. Consequently, the nuisance dust may be transported to distant sites and could induce adverse health effects. In addition the beneficial uses of NPs in drug delivery, cancer treatment, and gene therapy may cause unintentional human exposure. Because of our lack of knowledge about the health effects associated with NP exposure, we have an ethical duty to take precautionary measures regarding their use. In this review we highlight the possible toxic human health effects that can result from exposure to ultrafine particles (UFPs) generated by anthropogenic activities and their cardiopulmonary outcomes. The comparability of engineered NPs to UFPs suggests that the human health effects are likely to be similar. Therefore, it is prudent to elucidate their toxicologic effect to minimize occupational and environmental exposure. Highlighting the human health outcomes caused by UFPs is not intended to give a lesser importance to either the unprecedented technologic and industrial rewards of the nanotechnology or their beneficial human uses.

Carbon nanotubes: a review of their properties in relation to pulmonary toxicology and workplace safety

Carbon nanotubes (CNT) are an important new class of technological materials that have numerous novel and useful properties. The forecast increase in manufacture makes it likely that increasing human exposure will occur, and as a result, CNT are beginning to come under toxicological scrutiny. This review seeks to set out the toxicological paradigms applicable to the toxicity of inhaled CNT, building on the toxicological database on nanoparticles (NP) and fibers. Relevant workplace regulation regarding exposure is also considered in the light of our knowledge of CNT. CNT could have features of both NP and conventional fibers, and so the current paradigm for fiber toxicology, which is based on mineral fibers and synthetic vitreous fibers, is discussed. The NP toxicology paradigm is also discussed in relation to CNT. The available peer-reviewed literature suggests that CNT may have unusual toxicity properties. In particular, CNT seem to have a special ability to stimulate mesenchymal cell growth and to cause granuloma formation and fibrogenesis. In several studies, CNT have more adverse effects than the same mass of NP carbon and quartz, the latter a commonly used benchmark of particle toxicity. There is, however, no definitive inhalation study available that would avoid the potential for artifactual effects due to large mats and aggregates forming during instillation exposure procedures. Studies also show that CNT may exhibit some of their effects through oxidative stress and inflammation. CNT represent a group of particles that are growing in production and use, and therefore, research into their toxicology and safe use is warranted.