editorial toxicity of nanomaterialsdownloads.hindawi.com/journals/bmri/2015/521014.pdf · carbon...

EditorialToxicity of Nanomaterials

Haseeb A. Khan1 and Rishi Shanker2

1Department of Biochemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia2Institute of Life Sciences, School of Science and Technology, Ahmedabad University, Ahmedabad 380009, India

Correspondence should be addressed to Haseeb A. Khan; khan [email protected]

Received 26 March 2015; Accepted 26 March 2015

Copyright © 2015 H. A. Khan and R. Shanker. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

This decade has seen revolutionary developments in the fieldof nanotechnology with newer and diverse applications ofnanoparticles (NPs) appearing every day. However, thereare limited data about the toxicity of nanoparticles andtheir fate in biological systems. Inhalation, ingestion, anddermal penetration are the potential exposure routes fornanoparticles, whereas particle size, shape, surface area,and surface chemistry collectively define the toxicity ofnanoparticles. Increased production and intentional (sun-screens, drug delivery) or unintentional (environmental,occupational) exposure to nanoparticles are likely to increasethe possibilities of their adverse health effects. It is cruciallyimportant that novel nanomaterials must be biologicallycharacterized for their health hazards to ensure risk-free andsustainable implementation of nanotechnology.

Although NPs have always occurred in nature, the latestdevelopments are in the production and use of engineeredNPs which are finding applications in a wide range of areasincluding cosmetics, medicine, food and food packaging,bioremediation, paints, coatings, electronics and fuel cat-alysts, and water treatment. The drugs encapsulated intonanoparticles result in a clump-free, stable, and water-soluble material due to a very large surface to volume ratio.Nanoparticle-mediated drug delivery systems are being de-veloped for preventive treatment of the oxidative damageimplicated in various neurodegenerative diseases such asAlzheimer’s disease, Parkinson’s disease, andWilson’s disease.Novel nanomaterials are also being explored for potentialtherapeutic and diagnostic applications in cancer treatmentand diagnosis where the nanoscale properties facilitate theentry and intracellular transport to specific target sites. Nano-materials also hold great promise for reducing the production

of wastes and industrial contamination and improving theefficiency of energy production and use. The potential fornanotechnology is believed to be practically limitless andthe potential for profiting from creating and marketing theseadvances is the driving force behind an incredibly rapid rushto deliver these applications to the marketplace.

However, the production, use, and disposal of manu-factured NPs lead to discharges into air, soils, and aquaticsystems. Therefore, it is crucial to investigate their transportinto and through the environment and their impacts onenvironmental health. The indiscriminate use of engineeredNPs with unknown toxicological properties might pose avariety of hazards for environment, wildlife, and humanhealth. Our knowledge of the harmful effects of nanoparticlesis still very limited and at present no specific regulations havebeen developed for NPs usage. Since the nanomedicine andnanotoxicology are two sides of the same coin, the worthof this coin depends on its prudent use. There is potentialrisk for the exposure of humans and the environment tonanoparticles throughout their life cycle, starting from man-ufacture to disposal. Accidental spillages or permitted releaseof industrial effluents in waterways and aquatic systems mayresult in direct exposure to nanoparticles of humans via skincontact, inhalation of water aerosols, and direct ingestionof contaminated drinking water or particles adsorbed onvegetables or other foodstuffs.The small size of NPs facilitatestheir uptake into cells and translocation across epithelialand endothelial cells. NPs may travel to other places inbody and interact with tissues prolonging their stay in thebody. There is predominant accumulation of NPs in organswith high phagocytic activity, mainly in liver, kidney, andspleen. Toxic effects have been documented at the pulmonary,

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015, Article ID 521014, 2 pageshttp://dx.doi.org/10.1155/2015/521014

2 BioMed Research International

cardiac, reproductive, renal, cutaneous, and cellular levels.A precautionary approach is required for individual eval-uation of new nanomaterials for potential risks to healthand environment associated with the application of thesenanomaterials. Although current toxicity testing protocolsmay be applicable to identify harmful effects associated withnanomaterials, research into new methods is necessary toaddress the special properties of nanomaterials.

This special issue is a collection of 16 peer-reviewedoriginal research and review articles, describing the toxico-logical properties and biocompatibility of the commonly usednanomaterials. Most of the articles in this special issue aredevoted to carbon nanomaterials. Carbon is nonmetallic withpeculiar property of being able to bond with itself and a widevariety of other elements. Natural carbon exists in two differ-ent forms: graphite and diamond. Three additional forms ofcarbon including fullerenes, nanotubes, and graphene werediscovered between 1985 and 2004. Owing to their nanoscalestructure, these forms of carbon were classified as carbonnanomaterials. Graphene is a two-dimensional, atomic-scale,and hexagonal lattice in the form of a flat carbon sheet. Itis the basic structural element of other allotropes, includingcarbon nanotubes and fullerenes. Fullerenes are sphericalcarbon-cage molecules with sixty or more carbon atoms andmeasure about 0.7–1.5 nm in diameter. Carbon nanotubes(CNTs) are seamless cylinders of one or more layers ofgraphene with open or closed ends. Carbon nanotubes arethe third most widely used materials due to their significantproperties like thermal stability, lower mass density, and highmechanical strength. CNTs have now been incorporated inmore than 35 products for the various applications such assporting goods, automotive vehicles, clothing, electronics,and computers. The widespread use has enhanced theirannual production globally from 300 tons in 2006 to about4500 tons in 2011. The lipophilic nature, higher reactivity,and long life span of CNTs can adversely impact humanhealth and environment. CNTs can easily pass the biologicalbarriers and get distributed into the cellular and subcellularorgans, but their toxicity is concentration dependent. It hasbeen observed in the mice that inhalation exposure cancause pleural fibrosis in some cases; it is also reported thatit shows the toxicological activities like asbestos and leadsto the mesothelioma and granuloma. The toxicity studiesin vitro in cell lines demonstrated reactive oxygen species(ROS) generation, inflammatory responses, DNA-damage,and oxidative damage of proteins. The ecotoxicity of CNTshas been assessed in bacteria, protozoans, crustaceans, andfishes. For example, CNTs affect the ingestion and digestionin ciliated protozoa, ultimately reducing bioavailability of freeiron in the marine environment. There is a need to developthemethodologies and techniques to detect, characterize, anddetermine the transformation of CNTs in environment andbiological systems. The rise in the use of CNTs demandshealth and safety standards for CNT manufacturing opera-tions that potentially generate airborne particulate matter.

Some articles in this issue describe the toxicities of metaloxide NPs including three articles devoted to the toxicityof iron oxide NPs and one on the toxicities of nickel andcerium oxide NPs. One article reported the toxicity and

tolerance of zerumbone-loaded nanostructured lipid carrierin amousemodel.There are two review articles in this specialissue that focus on the general aspects of advantages anddisadvantages (toxicity) related to applications of differenttypes of NPs. Although there is a general recognition thatnanotechnology has the potential to advance science andquality of life and to generate substantial financial gains, anumber of reports have also suggested that potential toxicityshould be considered as a primary concern for safe use ofnanoparticles. The current knowledge of the toxic effects ofnanoparticles is relatively limited. A precautionary approachis therefore required for evaluation of potential risks to healthand environment associated with the use of nanomaterials.Although current toxicity testing protocols may be applied toidentify harmful effects of NPs, research into newmethods isrequired to address the special properties of nanomaterials.It is crucially important to assess their safety for sustainableimplementation of nanotechnology with its full potential.

Haseeb A. KhanRishi Shanker

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