Page 381 - IJB-9-2

International Journal of Bioprinting 3D gel-printed β-TCP/TiO2 porous scaffolds for cancellous bone tissue engineering

peak formed at 689 cm and 533 cm -1[37] . As expected, concentration, and temperature. While designing the
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the characteristic peak of TiO appeared distinctly in the printing ink formula, we choose gelatin with good
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infrared spectrum of β-TCP/5-TiO ceramic powder. biocompatibility as the main mobile phase because its
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Therefore, TiO was uniformly distributed and well-bound temperature-sensitive characteristics could help with
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to the β-TCP matrix. molding. Therefore, in this part, we mainly explored the
influence of different inorganic salt addition and PVA
Figure 1A showed that the surface of ceramic samples was solution addition on printability and formability of the
smooth without apparent cracks, but the volume of samples stent (Figure 2). We found that the increase of inorganic
shrank because the ceramics became more compact after salt content made ink extrusion difficult, but the addition
sintering. The volume shrinkage rate is depicted in Figure 1E. of PVA component can effectively improve this problem.
The average volume shrinkage rate of the sintered β-TCP Therefore, in subsequent experiments, we chose 5% PVA as
ceramic was 33.73%. By contrast, the volume shrinkage rate one of the ingredients in the printing ink formula.
of β-TCP/TiO ceramic with different content of TiO (1–5
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wt%) were 35.38%, 33.42%, and 32.29%, respectively. The 3.3. Characterization of 3D β-TCP/TiO scaffolds
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results showed that the addition of TiO had little effect on Samples of β-TCP/TiO ceramics scaffolds in different
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the densification of β-TCP during sintering. filling rates were presented with perforative pipelines,
Micromorphologies of β-TCP/TiO ceramics with and interpenetrating pores were perceived in the ceramic
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different TiO contents were detected by SEM (Figure 1D). scaffolds. The square pore structure was neatly arranged,
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A few large holes were seen in all the ceramic billets and the pore diameter was uniform (Figure 3A). It showed
because in the process of sintering (scale plate in 200 μm), that the size of cavities inside the ceramic scaffold increased
crystal water, PVA, and gelatin volatilized, causing a gradually with a decrease in the filling rate. Similarly,
shrinkage of the ceramic volume. Nevertheless, the when the filling rate was 40%, the average macropore
migration of the ceramic moving phase cannot fill the diameter decreased to 0.25 mm (Figure 3D). As illustrated
position of volatile matter, leading to the generation of a in Figure 3C, with filling rates of 20%, 30%, and 40%, the
porous interior structure and large voids on the surface. average porosity of the 3D scaffolds was 79.32%, 66.34%,
Further observation in magnification (scale plate in and 62.49%, respectively. A higher filling rate often results
[40]
10 μm) revealed that ceramic grains were tightly packed in compact structures and a higher utility rate of space ,
and arranged to form some micropores. As implantation which was in line with the result obtained in this work that
materials, these micropores were conducive to the adhesion the average porosity decreased with the increase of the
of cells, facilitating the entry of nutrients and the expulsion filling rate.
of harmful metabolite . To our satisfaction, the average The average shrinkage rates of β-TCP/3-TiO scaffolds
[38]
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diameter of micropores of β-TCP and β-TCP/TiO ceramics with filling rates of 20%, 30%, and 40% were 56.51%,
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reflected that the average pore size gradually decreased with 54.96%, and 53.57%, respectively (Figure 3B). According to
the addition of TiO (Figure 1F). In addition, the uniform the data, as the filling rate increased, the average shrinkage
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distribution of cavities in different sizes also confirmed the rates decreased slightly. Filling rates were another factor
excellent dispersion in ceramic slurry, which played a vital of the compressive strength of scaffolds (Figure 3E). The
role in the subsequent biological 3D printing . strength of the β-TCP/5-TiO ceramics scaffolds was 0.81
[39]
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MPa, 1.87 MPa, and 2.69 MPa, respectively, with 20%,
The compressive strength of β-TCP/TiO ceramics is 30%, and 40% filling rates. It can be concluded that when
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indicated in Figure 1G. The compressive strength of β-TCP/ the content of TiO was 5 wt%, a higher filling rate in the
TiO ceramics increased by 283%, from 3.30 MPa to 8.59 preparation process contributed to higher compressive
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MPa, which meets the mechanical requirements of bone strength of the scaffolds.
repair scaffolds. Thus, the introduction of TiO significantly
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improved the mechanical performance of β-TCP and The appearance of β-TCP/TiO ceramics scaffolds with
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overcame shortcomings of the fragility of β-TCP ceramics. different TiO content is presented in Figure 4A. TiO
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This may be due to two reasons: first, the addition of TiO exhibited no effects affecting the appearance and internal
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promotes the densification degree of ceramics to a certain structure of the scaffolds. No collapse and surface defects
extent; second, TiO may also promote the crystallization were found after the introduction of TiO , but alteration
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of β-TCP, rendering the binary ceramic strong. of void morphology was detected. The mean micropore
diameter of β-TCP/TiO ceramics scaffolds was 3 μm,
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3.2. Printability of 3D β-TCP/TiO scaffolds which was a bit shorter than the micropore diameter in
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The printability of 3D β-TCP/TiO scaffolds is affected β-TCP scaffolds (Figure 4B). On the other hand, the content
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by the content and particle size of inorganic salts, PVA of TiO had a negligible role on the porosity of β-TCP/TiO
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Volume 9 Issue 2 (2023) 373 https://doi.org/10.18063/ijb.v9i2.673