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Carbon nanomaterials reinforced scaffolds for bone repair
scaffolds [6-8] . Multiple additive manufacturing mechanical, and biological properties. Recently,
technologies such as material extrusion, powder Huang et al. investigated 3D printed porous
[25]
bed fusion, vat photopolymerization, and material scaffolds containing aligned MWCNTs and
or binder jetting techniques have been explored nano-HA (nHA), mimicking the natural bone
for the fabrication of bone tissue engineering tissue from the nanoscale to macroscale level.
scaffolds using a wide range of materials [9-11] . MWCNTs with similar dimensions as collagen
PCL, a semi-crystalline aliphatic polymer, has fibers were coupled with nHA and mixed within
been successfully used by our group for bone a PCL matrix. PCL/HA/MWCNTs scaffolds
tissue engineering scaffolds. We investigated the exhibited increased mechanical properties, cell
degradation kinetics of such scaffolds as a function proliferation, osteogenic differentiation, and
of scaffold topology [12,13] , the effect of processing scaffold mineralization. Wang et al. assessed
[20]
conditions on the morphological development/ PCL, PCL/G, and PCL/CNTs from chemical,
microstructure formation during the printing physical, and biological points of view. Results
process [14,15] and surface modification strategies confirmed that the addition of both G and
to improve cell attachment, proliferation, and CNT allows the fabrication of scaffolds with
differentiation [16,17] . To improve the bioactivity of improved properties. It also showed that scaffolds
PCL scaffolds, PCL/HA and PCL/TCP scaffolds containing G present better mechanical properties
containing different amounts of ceramic particles and high cell-affinity improving cell attachment,
were also investigated and the results showed that proliferation, and differentiation.
scaffolds containing HA present better human Graphene oxide (GO), a single monomolecular
adipose-derived stem cells (hADSCs) attachment layer of graphite with many functionalities including
and proliferation and TCP scaffolds present the presence of carbonyl, carboxyl, epoxide, and
improved mechanical properties. Despite the hydroxyl groups , is a candidate material for the
[26]
promising results obtained with these scaffolds, fabrication of electro-active scaffolds. Scaffolds
they are not electrically conductive, which is containing GO (concentrations up to 1.5 wt.%
a limiting characteristic of bone regeneration. and 5 mg/mL) produced through a wide range of
To address this issue, our group also developed non-additive manufacturing techniques have been
strategies to induce electroconductive properties reported [27-29] . Results suggest that due to the presence
on PCL-based scaffolds by mixing PCL with of GO produced scaffolds presented no cytotoxicity
conductive polymers or with low concentration against hADSCs, controlled degradation, and
[18]
of other conductive materials such as graphene enhanced protein adsorption. This paper investigates
(G) and carbon nanotubes (CNTs) [17,19,20] . the mechanical, wettability, and biological properties
The previous studies demonstrated that the of PCL scaffolds containing different concentrations
addition of low concentration of G (up to 1 of G or GO produced through material extrusion
wt.%), two-dimensional single-atom-thick sheets additive manufacturing .
[30]
of carbon atoms bound in hexagonal lattice
structures , can enhance the hydrophilicity, 2 Materials and methods
[21]
topology, and the mechanical property of PCL 2.1 Scaffolds fabrication
scaffolds [17,22] . The in vitro biological studies
show that cell attachment, proliferation, and G nanosheets were synthesized from graphite
differentiation of hADSCs can be stimulated by by water-assisted liquid-phase exfoliation as
the addition of G fillers [20,22,23] . Huang et al. reported before by Wang et al. and GO nanosheets
[24]
investigated the use of additive manufacturing to (Sigma-Aldrich, UK) were purchased from
produce scaffolds containing different loadings Sigma-Aldrich. G and GO nanosheets were
of multi-walled CNT (MWCNT) (0.25, 0.75, mixed with PCL pellets (CAPA 6500) (Perstorp,
and 3 wt.%). Results showed that the addition UK) through a melt blending process at different
of MWCNTs enhances protein adsorption, concentrations (1 wt.%, 2 wt.%, and 3 wt.%). PCL

62 International Journal of Bioprinting (2020)–Volume 6, Issue 2