Page 535 - IJB-9-6

International Journal of Bioprinting High-performance SrCS scaffolds via vat photopolymerization

where F max is the maximum standard load, and S is the solution mixture was 200 mg/mL. The mixed solution was
cross-sectional area of the scaffold. The elasticity modulus incubated at 37°C and 120 rpm in a constant temperature
E and energy absorption were calculated using Equations shock incubator, and the extract was filtered and collected
m
V and VI, respectively. after incubation for 72 h. The rBMSCs were seeded in 96-
3

E / � (V) well plates (cell density 4 × 10 cells/well) and cultured in a
c
m
constant temperature incubator at 37°C in a dehumidified
atmosphere of 5% CO 2 [38] . After 24 h of culture, the same
E (VI) volume of the original medium was replaced by 120 μL of
f xdx
a composite ceramic medium. The original medium without
composite bioceramic extract was used as the control group.
where is compressive strain, and (x) is the compressive
stress–strain curve. The average of each data point was Cell counting kit-8 (CCK-8) tests were performed after 1
and 7 days of culture. A 450 nm absorbance microplate
taken from five tests.
reader (BioTek, USA) was used to measure the optical
2.5. Characterization density (OD) value of the cell viability assays.
The thermal polymer PVT rheometer (Gottfert-RG50, Following seeding on the wafers and culturing
Gottfert, Germany) was used to measure the rheological for 24 h for rBMSCs, these wafers were fixed in 4.0%
behavior of the suspensions, at variable shear rates of paraformaldehyde and stained with rhodamine B-labeled
0–1000 s and a constant shear rate of 100 s . The UV phalloidin (Solarbio, China) and 4´,6-diamidino-2-
−1
−1
absorption range of SrCS-BTA powders was tested by phenylindole (DAPI) (Solarbio, China) for further analysis.
ultraviolet (UV)-visible spectrophotometer UV-2 (Lambda Then, we used a fluorescence microscope (Nikon Eclipse
35, PerkinElmer, USA). The Fourier transform infrared Ti; Nikon, Japan) to capture fluorescence images.
spectrometer (Nicolet iS50R, Thermo Scientific, USA)
was used to observe the characteristic absorption bands 3. Results and discussion
change of the chemical bonds. The thermal dilatometer
(DIL402C, NETZSCH, Germany) was used to real-time 3.1. Characterization of raw powders
monitor the densification process of ceramic samples, In the context of the ceramic VPP process, the agglomeration
from room temperature to 1300°C with a heating rate of of nanoscale powders (< 500 nm) is facilitated by the
10°C/min. The microstructure was analyzed by thermal stronger van der Waals force, which in turn leads to an
field emission scanning electron microscope (JSM-7600F, amplified scattering effect and a diminished curing depth.
Nippon Electronics, Japan) coupled with an energy Conversely, particles with sizes exceeding 35 μm are prone
dispersive spectroscopy (EDS). The phase composition was to sedimentation and could result in the generation of
observed by an X-ray diffractometer (XRD-7000, Shimadzu single layer with uneven thickness [39-41] . Therefore, we
Company, Japan), with a Cu tube (λ = 1.5406 Å), and at a selected irregular-shaped SrCS powders with an average
scanning rate of 2°/min. The main peak ratios of CaSiO particle size of 3.9 μm for VPP (shown in Figure 2a and
3
and CaTiO were calculated according to Equation VII : b). The particle size distribution of raw SrCS powders was
[36]
3
in the range of 1 to 10 μm (D = 1.7 μm, D = 10.3 μm),
10
90
I
M%( I I )/ 1 I I (VII) satisfying the requirements of powder size for VPP. The
I
2
2
3
4
1
micromorphology and particle size distribution of BTA
where I and I are the intensity of the main and secondary powders are shown in Figure S1 (Supplementary File). The
1
2
peaks of the M phase, respectively, and I and I are the SrCS-BTA composite powders revealed an average particle
4
3
intensity of the main and secondary peaks of another size of 3.6 μm with a wider and left-shifting particle size
phase, respectively. distribution (shown in Figure 2d). This particle gradation
effect of the composite powders would be beneficial to
2.6. Biological experiment the deposition behavior of ceramic suspension and the
To determine the bioactivity of the composite bioceramic sintering densification at high temperatures .
[42]
scaffolds, rat bone marrow stromal cells (rBMSCs) were
cultured in the extract of composite bioceramic scaffolds in 3.2. Fabrication of bioceramic scaffolds
vitro to proliferate . The composite bioceramic scaffolds Ceramic suspension with high solid loading and
[37]
were soaked in Dulbecco’s Modified Eagle Medium/Nutrient low viscosity plays a crucial role in the VPP additive
Mixture F-12 (DMEM/F12, Hyclone, USA) with 10% fetal manufacturing process . As shown in Figure 3a, the
[43]
bovine serum (FBS; Gibco, USA) and 1% antimicrobial viscosity of suspensions with a solid loading of 45 vol.% was
penicillin and streptomycin. The concentration of the 4 Pa·s at a shear rate of 100 s . Such high viscosity would
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Volume 9 Issue 6 (2023) 527 https://doi.org/10.36922/ijb.1233