Page 377 - IJB-10-5

International Journal of Bioprinting Tunable anisotropic gyroid bioscaffolds

diffractometer (XRD; SmartLab 9 kW). The specimens 3. Result
were subjected to CuKα radiation (λ = 1.54059 Å) in the 3.1. Comparative study of the SMWH and
2-theta range of 10°–80°, with a scanning rate of 10°/min, conventional post-thermal processing
and operated at 45 kV and 200 mA.
3.1.1. Effect of processing conditions on physical
The compressive properties of the sintered ceramic properties of the sintered ceramic
specimens were evaluated by uniaxial compression The efficacy of SMWH process was studied through
tests using (INSTRON 68TM-50, USA). For each set studying the properties of 3D-printed and sintered
of 3D-printed ceramic specimens, including both cube ceramic cube. The effects of sintering dwell times under the
and gyroid structures, three samples were tested, and SMWH process and conventional debinding and sintering
the average results were recorded. For the cube samples, were investigated. Figure 4a presents the XRD spectra of
the load was applied along the build direction during 3D the ceramic cube specimens fabricated under different
printing to evaluate the mechanical properties enhanced processing conditions. For all specimens prepared through
by the SHPS process. To evaluate the anisotropic properties the conventional sintering (CS), a broad peak at 21.3° was
of the graded gyroid structures, compression tests were detected, corresponding to the amorphous structure of
performed along both the build (N) and transverse (T) the SiO . A low peak intensity was observed at 21.8° for
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directions (Figure 2c). The peak compressive strength CS120m, indicating the formation of cristobalite phase
before failure and the stress–strain behavior were recorded. under a prolonged dwell time. In contrast, almost all
The tests were carried out at a crosshead speed of 0.5 mm/ specimens fabricated through the SMWH process show
min until the specimen failed, following the ASTM C1424 predominate peaks for cristobalite at 21.8° and 36.1°. For
standard. MW120m, the intensity of the peaks increased significantly.
2.5. In vitro cell culture experiment More amorphous SiO transformed into crystal structure
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Bone marrow-derived mesenchymal stem cells when the dwell time increased. In comparison with the CS
(BMSCs; Cyagen, Hong Kong) were used to examine process, the SMWH process facilitates rapid and efficient
the cytocompatibility of the graded gyroid scaffolds, energy transfer due to the intrinsic features of MW
including γ.50-FGgy, γ.33-FGgy, and γ.25-FGgy, with heating, which also result in reduced activation energy
ϕ = 57.55%. The cell culture medium was prepared by for nucleation and enhanced crystallization during the
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α-MEM supplemented with 10% fetal bovine serum and sintering process.
1% penicillin/streptomycin. The scaffolds were disinfected The physical properties of the sintered ceramic cube
using an autoclave and then washed with phosphate- under different processing conditions were characterized
buffered saline (PBS). The cytocompatibility of the scaffolds in terms of their percentage shrinkage, relative density,
was evaluated by seeding BMSCs onto the scaffolds. After and the major crystalline structure. Figure 4b depicts
putting different scaffolds in the bottom of a 24 well-plate, shrinkage in the length (L), width (W), and height (H) of
1 mL BMSC suspension (2 × 10 cells/mL) was added the specimens. As the dwell time increased, all specimens
onto the scaffolds and pipetted for three times to ensure exhibited an increase in shrinkage across all dimensions
the cell suspension can permeate into the scaffolds. All (L, W, and H). For the SMWH process, the shrinkage
samples were cultured at 37°C in an incubator with 5% percentage of the specimens sharply increased from
CO . After 6 h of cell seeding, the well-plates were changed dwell time of 10 to 80 min, while the increase become
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to remove the unattached cells on the scaffolds. After 1, 3, less obvious when the dwell time further extended to 180
and 7 days of incubation, the cell viability was assessed by min. The highest shrinkage percentages were recorded as
Live/Dead kit according to the manufacturer’s protocol. 7.58%, 7.67%, and 8.25% in the L, W, and H dimensions,
The quantification of cell viability was determined by respectively. Similarly, the specimens prepared through
the ratio of the viable cells to all cells in eight randomly the CS process demonstrated similar trend of the
selected images. In addition, the cell number on scaffolds shrinkage percentage as the dwell time increases, but with
at different time points was evaluated by dissociating the considerably lower shrinkage percentage compared to the
cells with trypsin-EDTA solution and counted by the SMWH process. While all specimens fabricated through
hemocytometer. The cell density was calculated through CS process shrank almost isotropically, a higher percentage
normalizing the cell number by the surface area of the of shrinkage in H compared to W and L was recorded for
scaffolds. To investigate the effects of the graded structure the specimens prepared through the SMWH process. This
on cell proliferation, a uniform gyroid structure with the is because during the layer-by-layer printing process, the
same value of ϕ, i.e., 57.55% (57.55VF-gy), was also used sedimentation of ceramic powder creates a resin-rich
for comparison. region on top of each printing layer, forming a lamellar

Volume 10 Issue 5 (2024) 369 doi: 10.36922/ijb.3609