Toxic nanoscale materials

Oxidative catalysis over metal oxides yields mainly HC1 and C02. Catalysts such as V203 and Cr203 have been used with some success.49 50 In recent years, nanoscale MgO and CaO prepared by a modified aerogel/hypercritical drying procedure (abbreviated as AP-CaO) and AP-MgO, were found to be superior to conventionally prepared (henceforth denoted as CP) CP-CaO, CP-MgO, and commercial CaO/MgO catalysts for the dehydrochlorination of several toxic chlorinated substances.51 52 The interaction of 1-chlorobutane with nanocrystalline MgO at 200 to 350°C results in both stoichiometric and catalytic dehydrochlorination of 1-chlorobutane to isomers of butene and simultaneous topochemical conversion of MgO to MgCl2.53-55 The crystallite sizes in these nanoscale materials are of the order of nanometers ( 4 nm). These oxides are efficient due to the presence of high concentration of low coordinated sites, structural defects on their surface, and high-specific-surface area. 

An additional factor which may modify the lung toxicity and corresponding risk following exposures to engineered nanoparticulates is the electrostatic attraction/aggregation or agglomeration potential of some nanoscale materials, such as single wall carbon nanotubes (SWCNT). The dimensions of individual SWCNTs have been reported as Inm (diameter... 

Nanoscale materials are known to have various shapes and structures such as spherical, needle-like, tubes, platelets, and so on. The effects of the shape on the toxicity of nanomaterials are unclear. The shape of nanomaterials may have effects on the kinetics of deposition and absorption to the body. Inhaled particles in the nanosize range can certainly deposit in all parts of the respiratory tract including the alveolar region of the lungs. Dependent upon the specific application, oral, dermal, and other routes of exposure are also possible for nanoparticles. Because of their small size, they may pass into cells directly through the cell membrane or penetrate the skin and distribute throughout the body once translocated to the blood circula-... 

Nanocrystalline cellulose, a rod-shaped nanoscale material with exceptional strength and physicochemical properties, can be prepared from inexpensive renewable biomass. Besides its potential use as a reinforcing agent for industrial biocomposites, pristine NCC exhibits low toxicity and poses no serious environmental concerns, providing impetus for its use in bioapplications [115]. 

At the same time, NIOSH recognizes that the same novel characteristics of engineered nanoscale materials that make them attractive for research and development purposes may also mean that their fundamental toxicity characteristics differ from their bulk counterparts. Thus, commercialization must be balanced against preventing reasonably foreseeable injuries which might accompany any exposure to engineered nanoscale materials in the workplace. 

Office of Pollution Prevention and Toxics, 2009. Nanoscale Materials Stewardship Program, Interim Report. Environmental Protection Agency, Washington, DC. Available at . 

Under pressure to provide interim guidance, particularly under the Toxic Substance Control Act (TSCA), EPA in July 2007 issued guidance on determining whether a new nanoscale material is considered an existing chemical covered by inventory listing or a new chemical subject to Premanufacture Notification (PMN) reporting requirements. Specifically, are nanomaterials automatically considered New Chemicals under the TSCA or may they be considered as Existing Chemicals ... 

EPA Nanoscale Materials Stewardship Program. EPA has implemented a voluntary Nanoscale Materials Stewardship Program (NMSP) under the Toxic Substances Control Act (TSCA), which is intended to "complement and support its efforts on new and existing nanoscale materials.EPA indicates that, based on the outcomes of an extensive review process, the general components of the Stewardship Program could include ... 

The first news report on the potential damaging effects of nanoscale materials surfaced about a decade ago, when TiO JTnO nanoparticles from sunscreen were found to cause free radicals in skin cells, damaging DNA. Since then, there have been an increasing number of such reports suggesting that nanostructures are able to traverse across membranes in the body, with an increasing toxicity with decreasing nanoparticulate dimensions. Perhaps the most widely reported study surfaced in mid-2004, where it was shown that fuUerenes, a nanoscale aUotrope of carbon, cause brain damage in aquatic species. 

One of the main sources of toxicity of metallic nanoparticles appears to be the electronic and/or ionic transfers occurring during the oxido-reduction, dissolution, and catalytic reactions either within the nanoparticles lattice or on release to culture medium. The effects of nanoscale materials on biological systems are vital for the industrial production and their safe application in daily life and biomedicine. XAS is a powerful tool to investigate bio-nano interactions and can provide structural details of biomolecules at the interface of bio-nano systems. 

Cationic lipids and cationic polymers are designed as gene delivery systems on the nanoscale. Especially chitosan is under focus as a biodegradable, natural biopolymer, used both as the polyplex and also as a coating material for other polyplexes. Chitosan-coated poly(isohexyl cyanoacrylate) nanoparticles have also been developed for intravenous delivery of siRNA and no evidence of toxicity was observed after intravenous administration for 30... 

Yang L, Webster T. Biological responses to and toxicity of nanoscale implant materials. In Ehaz N, editor. Degradation of implant materials. New York Springer 2013. p. 481-508. 

Nanoscale debris from CoCrMo, which is also a widely used orthopedic implant material, may also induce DNA and chromosome damage as well as cytotoxicity. For instance, CoCr nanoparticles demonstrated more severe DNA damage, chromosomal damage, and toxic effects compared to micron-sized CoCr particles [8,9]. For orthopedic implants made of stainless steels, Fe or Ni nanoparticles are also possible sources for triggering toxicity and adverse effects at local or systemic levels. For example, Ni particles implanted in rat soft tissues were found to cause just allergic reactions when... 

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