The Emerging Applications of Graphene Oxide and Graphene in Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 282

Therefore, extensive research has been conducted to improve the mechan-
ical properties of this material. According to He et al ., adding 4 wt% GO
to alginate increased its Young's modulus and maximum tensile strength
from 1.9 and 0.32 to 4.3 and 0.62 GPa, respectively, owing to the uniform
dispersion of GO within the alginate matrix [59]. The latter composite was
obtained using the wet spinning approach and was water soluble and
nontoxic to cartilage cells. Another study demonstrated that GO was able
to chemically react with the chitosan scaffold [60]. This reaction occurred
between the carboxyl groups of GO and the amine groups of chitosan.
GO enhanced the biocompatibility and degradation of chitosan scaffolds.
Highly porous and interconnected GO/chitosan scaffolds facilitated the
adhesion of osteoblast cells and their proliferation within the scaffolds.
In addition, the negatively charged carboxyl groups of the GO compo-
nent were recognized as important for effective cell-scaffold interactions.
Chitosan as extracted from the natural chitin is a useful biomaterial to
repair chondral and osseous problems. However, a requirement must
be met to improve the biological response and mechanical properties of
this material for bone TE [61]. The latter study was a successful trial of
GO to fulfi ll this requirement. Wan and Chen [62] reported the success-
ful synthesis of PCL/GO composites, showing that adding 0.3 wt% GO
improved the modulus, tensile strength, and energy at breakage of the
PCLs by 66%, 95%, and 416%, respectively. In addition, the bioactivity of
PCLs during biomineralization was increased due to the presence of GO.
Mechanical improvements in PCL/GO composites compared to pristine
PCLs were attributed to changes in the morphology of the fi bers and the
reinforcement of PCL due to the GO component, while the improvement
in bioactivity was due to the anionic functional groups of GO, which
largely enhanced the nucleation process and therefore the biomineral for-
mation of the composites. The high porosity of the PCL/GO composites
( 94%) is a signifi cant advantage for biomedical applications. While PCL

has been approved by the US Food and Drug Administration (FDA) as
a biodegradable polymer for particular medical applications (e.g., drug
delivery device and suture), its poor mechanical properties have limited
its application to hard TE. Researchers hope that PCL/GO biocomposites
will fi nd novel applications as tissue scaffolds and biomedical devices,
particularly in orthopedics. Taken together, GO demonstrated great infl u-
ence on the currently used scaffolds to improve their properties, such as
cellular responses and mechanical properties. Note that graphene-based
materials (e.g., GO and graphene) as the supplementary components for
the scaffolds are superior to their CNTs counterparts in terms of cytotox-
icity effects. The main reason could be metal catalysts used in the fab-
rication procedure of CNTs, which can remain inside the nanotubes.
Those metals have potential negative effects on the cell survival and
growth [63].

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