A Review on Biomedical Applications of Single-Walled Carbon Nanotubes

Identifying the pulmonary hazard of high aspect ratio nanoparticles to enable their safety-by-design

High aspect ratio, or fiber-shaped, nanoparticles (HARNs) represent a growth area in nanotechnology as their useful properties become more apparent. Carbon nanotubes, the best known and studied of the HARNs are handled on an increasingly large scale, with subsequent potential for human inhalation exposure. Their resemblance to asbestos fibers precipitated fears that they might show the same type of pathology as that caused by asbestos and there is emerging evidence to support this possibility. The large number of other HARNs, including nanorods, nanowires and other nanofibers, require similar toxicological scrutiny. In this article we describe the unusual hazard associated with fibers, with special reference to asbestos, and address the features of fibers that dictate their pathogenicity as developed in the fiber pathogenicity paradigm. This paradigm is a robust structure:toxicity model that identifies thin, long, biopersistent fibers as the effective dose for fiber-type pathogenic effects. It is likely that HARNs will in general conform to the paradigm and such an understanding of the features that make fibers pathogenic should enable us to design safer HARNs.

Toxicology of nanomaterials used in nanomedicine

With the development of nanotechnology, nanomaterials are being widely used in many industries as well as in medicine and pharmacology. Despite the many proposed advantages of nanomaterials, increasing concerns have been expressed on their potential adverse human health effects. In recent years, application of nanotechnology in medicine has been defined as nanomedicine. Techniques in nanomedicine make it possible to deliver therapeutic agents into targeted specific cells, cellular compartments, tissues, and organs by using nanoparticulate carriers. Because nanoparticles possess different physicochemical properties than their fine-sized analogues due to their extremely small size and large surface area, they need to be evaluated separately for toxicity and adverse health effects. In addition, in the field of nanomedicine, intravenous and subcutaneous injections of nanoparticulate carriers deliver exogenous nanoparticles directly into the human body without passing through the normal absorption process. These nanoparticulate carriers themselves may be responsible for toxicity and interaction with biological macromolecules within the human body. Second, insoluble nanoparticulate carriers may accumulate in human tissues or organs. Therefore, it is necessary to address the potential health and safety implications of nanomaterials used in nanomedicine. Toxicological studies for biosafety evaluation of these nanomaterials will be important for the continuous development of nanomedical science. This review summarizes the current knowledge on toxicology of nanomaterials, particularly on those used in nanomedicine.