The Emerging Applications of Graphene Oxide and Graphene in Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 277

graphene can also be used to effectively conduct the electrical current within
the scaffold and therefore increase the effi ciency of electrical manipulation
techniques (e.g., electrical stimulation) of cell and tissue constructs. This
property is in particular of great advantage for the electro-active cells, such
as muscle [9, 10] and cardiac cells [11, 12], where the electrical stimulation
has been used as a valuable tool to fabricate the corresponding engineered
tissues. Interestingly, a recent study revealed that various cellular behav-
iors, such as cell adhesion, proliferation, and differentiation, are infl uenced
by the passive conductivity of scaffolds [13].
Graphene is a thin (single-atom-thick) sheet of hexagonally-bonded
carbon atoms forming a two-dimensional (2D) honeycomb lattice struc-
ture. Since its exfoliation from graphite in 2004 (see Figure 12.1) [14], gra-
phene has attracted a great deal of attention in the scientifi c community
due to its extraordinary electronic, thermal, mechanical, and optical prop-
erties [14-18]. Graphene and its derivatives are a relatively new class of
materials for biomedical applications. The fi rst breakthrough work in this
area was reported by Liu et al. , who used GO (Figure 12.1) as an effi cient
drug delivery system [19]. Subsequently, an enormous amount of interest-
ing research has been performed to explore the biomedical applications of
these functional materials as aforementioned TE scaffolds, antimicrobials
[20], drug/gene carriers [21], and biological sensors [22] and detectors [23].
GO and its reduced form have been prepared in freestanding sheets and
shown that they have signifi cant antibacterial property [24]. Akhavan et al.
demonstrated the antibacterial effect of GO and reduced GO as deposited
on stainless steel substrates [25]. They used Gram-negative Escherichia coli
and Gram-positive Staphylococcus aureus as bacteria models. It was found
that the reduced GO was more toxic to the bacteria than the GO likely due
to higher charge transfer of the reduced GO compared to the GO while

Oxidation Dispersion Reduction

Graphene Oxide
(GO)

Graphene

Graphite Exfoliated GO

Figure 12.1 Procedure used to fabricate GO and graphene from natural graphite.
Graphite is typically oxidized under a harsh acidic environment to obtain GO.
GO with oxygen-containing functional groups is then exfoliated into single
layers of GO in aqueous solution. GO can then be reduced to obtain graphene.
Grey, red, and white circles represent carbon, oxygen, and hydrogen atoms,
respectively.