Page 96 - IJB-6-1

Graphene oxide accelerates degradation of poly-l-lactic acid scaffold
To accelerate the degradation of PLLA, different ratios of GO were studied by observation
Kang et al. blended collagen and PLLA, using of degradation morphology and measurement of
collagen’s natural fast degradability to accelerate mass loss. Meanwhile, degradation mechanism
degradation. Nevertheless, the introduction of was also analyzed. Besides, surface and fracture
collagen decreased the mechanical strength of morphologies of the scaffold were also observed
the PLLA scaffold . Considering that PLLA is to further investigate the causes of changes in
[16]
formed by the linkage of ester bonds between lactic mechanical properties. In addition, bioactivity
acid monomers, its degradation is first caused by and cytocompatibility had also been evaluated by
the hydrolysis of the ester bond in the main chains simulated body fluid (SBF) immersion and cell
and then decomposes into carbon dioxide and proliferation experiments, respectively.
water . PLLA is a hydrophobic material and is
[17]
not beneficial for the intrusion of water molecules 2 Materials and methods
into its interior to break the ester bonds, making
it difficult to degrade . Therefore, promoting the 2.1 Materials and preparation
[18]
contact between water molecules and the ester PLLA powders (Purity: tionigand inherent
bond of PLLA is an effective method to accelerate viscosity: 1.46 dl/g) were provided from Shenzhen
the hydrolysis of ester bonds. Polymtek Biomaterial Co., Ltd. (Shenzhen, China).
Graphene oxide (GO) is a two-dimensional GO powders (purity > 98%) were obtained from
lamellar structure with a large amount of oxygen- Chengdu Organic Chemicals Co., Ltd. (Chengdu,
containing functional groups (such as –COOH and China). The composition of phosphate-buffered
–OH) on its surface [19-22] . These functional groups solution (PBS) was NaCl, KCl, Na HPO2H O,
2
2
can endow GO good hydrophilic property and water and KH PO , which was provided from Sigma-
absorption capacity [23-26] . At the same time, the Aldrich (Beijing, China). SBF was purchased
4
2
lamellar GO with large surface area is likely to form from Qingdao Jieshang Biological Technology
many interfaces with matrix, and these interfaces Co., Ltd. (Qingdao, China). Human osteoblast-
can be regarded as microchannels to facilitate water like MG-63 cells were supplied from the American
molecules to invade and induce the breaking of Type Culture Collection (ATCC, Rockville, MD).
ester bonds. Besides, GO with excellent mechanical Three-dimensional porous PLLA and PLLA/
properties (Young’s modulus >0.5 TPa, and tensile GO scaffolds with 0.3%, 0.6%, 0.9%, and
strength ~130 GPa) can be used as a reinforcing 1.2% GO were prepared by SLS. The powders
phase for scaffold [27,28] . In addition, it has also been were evenly laid on the sintering platform and
reported that GO possessed good biocompatibility selectively sintered according to the pre-planned
for cell adhesion and proliferation [29-31] . The
current reports mainly utilized GO to improve scaffold models, and the sintering platform
the mechanical properties, thermal stability, and would be lowered to a corresponding height
cytocompatibility of PLLA [32-35] whereas few when a layer of powders was sintered and then
studies focused on inducing ester bonds hydrolysis a layer of powders was applied again, sintering
of PLLA scaffold by GO to accelerate degradation. layer by layer, and finally obtaining the required
In this study, GO was introduced into PLLA scaffolds. The processing parameters were applied
to accelerate degradation, and three-dimensional as follows: Spot size of 1.2 mm, laser power of
porous PLLA/GO scaffolds were prepared by 2.2 W, and laser scanning speed of 100 mm/min.
selective laser sintering (SLS) , which is an 2.2 Characterization
[36]
additive manufacturing method , and can realize
[37]
the preparation of personalized scaffolds and Surface and fracture morphologies were observed
interconnected porous structures compared to by Phenom Scanning Electron Microscopy (FEI
traditional fabrication methods [38-42] . Degradation Co., USA), and energy-dispersive spectroscopy
properties of the PLLA scaffold containing (EDS) was used to examine the elemental content

92 International Journal of Bioprinting (2020)–Volume 6, Issue 1