Caitlin Fisher, Amanda E. Rider, Zhao Jun Han, Shailesh Kumar, Igor Levchenko, and Kostya (Ken) Ostrikov

“Applications and Nanotoxicity of Carbon Nanotubes and Graphene in Biomedicine,”

Journal of Nanomaterials

vol. 2012, Article ID 315185, 19 pages, 2012. doi:10.1155/2012/315185

4.1 Introductory Remarks

Graphene, a 2D carbon nanomaterial with a honeycomb-like structure, has been the subject of a considerable interest after being the subject of the 2010 Nobel Prize for Physics. Its unique properties, including ballistic electron transport [179, 180] at room temperature, tunable band-gap (for few-layer graphene), high chemical and mechanical stability, low electrical noise, high thermal conductivity, and biocompatibility, have led it to be used in many advanced devices ranging from ultra-capacitors to spintronic devices [181–186]. In line with the purpose of this paper, however, we will concentrate on the emerging biomedical-related applications of graphene and its derivatives (i.e., pristine graphene, graphene oxide, metal nanoparticle decorated graphenes, vertical graphene nanosheets, and many other hybrid structures) in biosensors, biocompatible scaffolds, tumor treatment, and drug delivery.

4.3. Nanosafety and Nanotoxicity of Graphene

As mentioned in Section 3, for any biological-related application, particularly in vivo applications, great care must be taken to ensure that the toxicity of the nanomaterial is well characterized and understood. Whilst this has been extensively done for carbon nanotubes, markedly fewer studies [158, 216–222] are available for graphenes (e.g., an ISI Web of Knowledge topic search on 03/01/2012 gave 59 hits for “graphene” and “toxicity” compared to 1668 hits for “nanotube” and “toxicity”). There is even less consensus as to the sagacity of using this next-generation material as an integral component in in vivo applications. Zhang et al. [158] compared the cytotoxicity level of graphene to that of carbon nanotubes in the case of neuronal PC12 cells. They found that toxicity was shape and composition dependent, with graphene overall having a lower toxicity than CNTs; however the toxicity of graphene was curiously found to be inverse to concentration [223], with graphene exhibiting a higher toxicity than CNTs at low concentrations [223]. Studies on the uptake of PEG-coated graphene nanosheets in mice and subsequent photothermal treatment of cancerous tumors did not show any adverse toxic effects [192, 215]. In other studies, however, sharp graphene nanosheet edges [216] have been shown to cause considerable damage to the cell membrane of bacteria, although this antibacterial property has the potential to be useful. Moreover, hydrophilic carboxyl-functionalized graphenes have been shown to be able to be internalized in cells without any toxic effects, in contrast to hydrophobic pristine graphene [224]. The biocompatibility of graphene oxide has also been studied, with toxicity shown to be dose-dependent in both humans and animals [225], with little to no effect for low and medium doses in mice [225]. Graphene oxide nanosheets were demonstrated to be biocompatible with yeast cells [226]. With the wide range of morphologies, coatings, and hybrid structures available for graphenes, more detailed and longer-term studies are required before serious in vivo biomedical graphene applications are implemented.

{reproduced with expressed permission}