Applications and Nanotoxicity of Carbon Nanotubes and Graphene in Biomedicine

Journal of Nanomaterials, May 2012

Owing to their unique mechanical, electrical, optical, and thermal properties, carbon nanostructures including carbon nanotubes and graphenes show great promise for advancing the fields of biology and medicine. Many reports have demonstrated the promise of these carbon nanostructures and their hybrid structures (composites with polymers, ceramics, and metal nanoparticles, etc.) for a variety of biomedical areas ranging from biosensing, drug delivery, and diagnostics, to cancer treatment, tissue engineering, and bioterrorism prevention. However, the issue of the safety and toxicity of these carbon nanostructures, which is vital to their use as diagnostic and therapeutic tools in biomedical fields, has not been completely resolved. This paper aims to provide a summary of the features of carbon nanotube and graphene-based materials and current research progress in biomedical applications. We also highlight the current opinions within the scientific community on the toxicity and safety of these carbon structures.

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Applications and Nanotoxicity of Carbon Nanotubes and Graphene in Biomedicine

Applications and Nanotoxicity of Carbon Nanotubes and Graphene in Biomedicine Caitlin Fisher,1,2 Amanda E. Rider,1,2 Zhao Jun Han,1,2 Shailesh Kumar,1,2 Igor Levchenko,1,2 and Kostya (Ken) Ostrikov1,2 1Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070, Australia 2Plasma Nanoscience at Complex Systems, School of Physics, The University of Sydney, Sydney, NSW 2006, Australia Received 7 March 2012; Accepted 29 March 2012 Academic Editor: Krasimir Vasilev Copyright © 2012 Caitlin Fisher et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Owing to their unique mechanical, electrical, optical, and thermal properties, carbon nanostructures including carbon nanotubes and graphenes show great promise for advancing the fields of biology and medicine. Many reports have demonstrated the promise of these carbon nanostructures and their hybrid structures (composites with polymers, ceramics, and metal nanoparticles, etc.) for a variety of biomedical areas ranging from biosensing, drug delivery, and diagnostics, to cancer treatment, tissue engineering, and bioterrorism prevention. However, the issue of the safety and toxicity of these carbon nanostructures, which is vital to their use as diagnostic and therapeutic tools in biomedical fields, has not been completely resolved. This paper aims to provide a summary of the features of carbon nanotube and graphene-based materials and current research progress in biomedical applications. We also highlight the current opinions within the scientific community on the toxicity and safety of these carbon structures. 1. Introduction Carbon nanotubes (CNTs) and graphene are very promising candidates to form the basis of new biological and medical devices. Carbon nanotubes can be thought of as rolled-up graphene sheets with no overlapping edges [1]. Their diameters typically vary from 1 to 100 nm and their lengths can be several orders of magnitude larger, up to millimeters, even centimeters long [2]. Various orientations of CNTs are shown in Figures 1(a)–1(c): randomly oriented, vertically aligned, and in a “dandelion-like” structure, respectively. The well-documented beneficial mechanical, electrical and chemical characteristics of CNTs and graphene [1, 3–7] as well as their ability to be hybridized with a wide range of organic and inorganic materials make them ideal candidates for many biomedical applications such as biosensing [8–12], tissue engineering [13–15], and drug delivery [16, 17]. Figure 1: Various orientations of CNTs grown using chemical vapor deposition on Si substrates: (a) entangled, randomly orientated CNTs; (b) vertically aligned CNTs; (c) dense “dandelion-like” CNT structure grown using plasma-enhanced chemical vapor deposition on an etched, catalyst-free Si substrate. Details on the growth of similar structures can be found in [40]. In the past two decades, intense efforts have been directed at providing specificity, selectivity, reproducibility, and robustness to these carbon nanostructures in biologically relevant environments [18–22]. However, the issue of toxicity of CNTs and graphene in living biological systems, which is vital for the successful incorporation of these materials into functional biomedical devices, remains unsolved at macroscopic, cellular, and intracellular levels [23–25]. In this paper we will, in Section 2, discuss the role of CNTs in biosensing, tissue engineering, and drug delivery. Aspects of the toxicity of CNTs in living biological systems are then discussed in Section 3 and the emerging graphene-related biomedical applications and associated safety issues are briefly presented in Section 4. Finally, a summary of this work and an outlook for future research is provided. 2. Applications of Carbon Nanotubes in Biomedicine Due to the chemical inertness of graphitic walls, functionalization of CNTs and graphene is often the key step required in any application of these materials. Let us first briefly consider the possible ways of performing such functionalization. 2.1. Functionalization of Carbon Nanotubes Successful functionalization should maintain the integrity of CNT’s mechanical, electrical, and chemical properties as well as the activity of the biological species being attached. In general, there are two CNT functionalization methods: covalent bonding and noncovalent wrapping [26–28]. Covalent bonding involves chemical attachment of the desirable species to the CNT [26], often at the tube ends or at defect sites [1, 29]. Oxidation processes are often used as a preparation step to create chemically active sites for covalent bonding [30]. These oxidation processes can be performed through wet chemical or dry plasma routes [30], amongst others. A variety of biological species ha (...truncated)


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Caitlin Fisher, Amanda E. Rider, Zhao Jun Han, Shailesh Kumar, Igor Levchenko, Kostya (Ken) Ostrikov. Applications and Nanotoxicity of Carbon Nanotubes and Graphene in Biomedicine, Journal of Nanomaterials, 2012, 2012, DOI: 10.1155/2012/315185