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Shuai C et al.

3.2 Phase composition the mechanical loss caused by chemical etching, 1 wt%
GO was incorporated into the PLLA scaffolds. The
The phase composition of scaffolds was analyzed using typical microstructure of GO/PLLA scaffold before
X-ray diffraction (XRD) within a wide 2θ range of chemical etching was presented in Figure 4(c). It could
5°~65° (Figure 3). Results presented typical broadened be seen that after the addition of GO, the GO/PLLA
patterns dominated by two diffraction peaks located at scaffold also exhibited a smooth and dense surface,
16.6° and 19.1°, which could been ascribed to the semi-
crystalline nature of PLLA. After NaOH etching process, showing no obvious differences compared with PLLA
no new diffraction peaks were detected, demonstrating scaffold shown in Figure 2(c1). The surface porous
the NaOH etching process did not lead to phase change. structure of GO/PLLA-1.0 scaffold was presented in
Figure 4(d). Similarly, little differences in the micropore
3.3 Mechanical properties structure were observed between the etched GO/PLLA-
1.0 scaffold and PLLA-1.0 scaffold. The compressive
Compression tests were performed to quantify the effect
of chemical etching on the mechanical properties of stress for GO/PLLA-0, GO/PLLA-0.5, GO/PLLA-1.0,
the multi-scale porous scaffolds. Figure 4(a) showed and GO/PLLA-1.5 were 32.2 ± 1.3 MPa, 28.3 ± 1.2
the representative stress-strain curves of the scaffolds MPa, 24.5 ± 2.1 MPa, 19.7 ± 2.3 MPa, respectively.
under compression tests. It could be seen that the stress Clearly, the incorporation of GO considerably improved
of PLLA-0 scaffold had a sudden drop at a maximum the mechanical properties of the etched scaffolds.
of 20.1 MPa, indicating the brittleness nature of PLLA. Specifically, the compressive strength of GO/PLLA-1.0
In comparison, the maximum stress of scaffolds after scaffold was approximately 41.6% and 10.3% higher
chemical etching gradually decreased. It was not than that of PLLA-1.0 scaffold and PLLA-0 scaffold,
surprising that the chemical etching process had a respectively. Moreover, the strength of fabricated
negative effect on the compressive properties of scaffold scaffolds was comparable to or even higher than that of
[31]
due to the increased porosity on scaffold surface. The cancellous bone (4-20 MPa) .
relationship between the compressive strength on etching Subsequent indentation tests revealed a similar trend
time was presented in Figure 4(b). As the etching time of the hardness with that of compressive strength, as
increased from 0 h to 1.5 h, the compressive strength showed in Figure 5. The hardness of PLLA-0 scaffold
of the scaffolds was considerably decreased by 30.1% could reach 22.21 ± 0.84 Hv, whereas the porous surface
from 22.2 ± 1.7 MPa to 15.5 ± 1.5 MPa. It was well structure by chemical etching impaired the hardness
known that scaffolds should have adequate mechanical of scaffolds, e.g. after etching for 1.5 h the hardness
properties to provide structural support for the new decreased by 18.7% to 18.05 ± 1.41 Hv in comparison
tissues after implantation . Therefore, to compensate to PLLA-0 scaffold. However, the hardness of scaffolds
[8]

Figure 3. XRD analysis of the phase composition of the scaffolds with and without chemical etching.

International Journal of Bioprinting (2018)–Volume 4, Issue 2 5