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International Journal of Bioprinting Sr-doped printed scaffolds for bone repair

for better fit at the bone defect site and more effective bone scaffolds possessed strong mechanical properties and
defect repair. 48–50 In this study, P and SBP scaffolds were could withstand greater mechanical loads. In Figure 5A,
prepared by 3D printing, and PSBP scaffolds were obtained the thermogravimetric analysis revealed that the mass of
by co-deposition of PDA with SBP scaffolds. The physical the remaining inorganic particles in each scaffold group
properties, biocompatibility, and immunomodulatory was close to the theoretical proportion of the mixed SrBG,
ability of the scaffolds were evaluated by in vitro and and all three scaffolds exhibited good thermal stability.
in vivo experiments, and the effects of the scaffolds toward Biocompatibility of the stent is a prerequisite for its
osteogenic differentiation in vitro and bone defect repair biological functioning. As presented in Figure 6A, the
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in vivo were assessed.
results of the live-dead cell assay indicated that the PSBP
The three scaffold groups (P, SBP, and PSBP) were scaffold had a higher number of adhered and proliferated
characterized accordingly. Firstly, the surface morphology BMSCs compared to the other scaffold groups, indicating
of the scaffolds was observed by SEM (Figure 4A). There non-cytotoxicity. Meanwhile, results of the CCK-8
was no significant difference in the pore size among the proliferation assay indicated that the PSBP scaffold
three scaffold groups. However, after SrBG addition and could promote BMSC proliferation significantly better
PDA modification, the PSBP scaffolds had SrBG particles than the other scaffold groups, which was consistent
attached to their surface, resulting in smaller and fewer with the live-dead cell staining results. However, the
surface pores and a smoother surface. Secondly, good scaffold degradation products post-implantation and the
porosity is necessary for the scaffold to fulfill its bone repair substances generated by their interaction with the body’s
function. As displayed in Figure 4C, all three scaffold microenvironment may be potentially toxic to the host.
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groups exhibited high porosity, with PSBP scaffolds having To evaluate the in vivo toxicity of the scaffolds, an SD rat
a slightly lower porosity than P and SBP scaffolds. This is model was established in this study. HE staining analysis
due to the filling of some pores during PDA modification of liver and kidney tissues revealed no obvious damage or
of the SBP scaffolds. It is further demonstrated by the abnormal reaction, highlighting the good biosafety for all
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average aperture of each group of scaffolds as shown in three scaffold groups (Figures 9 and 10).
Appendix Figure A1, where the smallest average aperture Ideal bone repair materials must be biocompatible
of the scaffolds was observed in the PSBP group. The high and possess strong osteogenic differentiation capacity.
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porosity of the scaffolds facilitates cell adhesion, growth, However, PCL is limited by its insufficient osteogenic
and vascular ingrowth. Nonetheless, the differences capacity, high hydrophobicity, and lack of sufficient cell
50
between the scaffold groups were not significant, and the attachment sites. 60,61 To overcome these shortcomings,
slight decrease in porosity had little effect on cell growth Hench et al. used the sol–gel method to prepare SiO -
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and angiogenesis. PDA in the PSBP scaffolds filled the CaO-P O ternary BGs, characterized by numerous
2
fiber pores, significantly enhancing their compressive microporous structures, a large specific surface area, and
2
5
properties (Figure 5B1 and B2) and inhibiting Sr² release a fast rate of surface hydroxyapatite (HA) generation,
+
(Figure 4D) compared to SBP scaffolds. Moreover, filling enabling them to form strong chemical bonds with
the porous structure on the fibers increased the scaffolds’ human bone tissue. In this study, SrBG was compounded
compressive strength and reduced their degradation rate, in PCL scaffolds, and the scaffolds were modified using
consistent with the trends observed in a previous study. PDA to detect osteogenesis-related genes. ALP is a
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Studies have demonstrated that PDA functionalization of phenotypic marker of early osteogenesis. As displayed in
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scaffold surfaces strongly attaches reactive groups—such Figure 7A1 and A2, the PSBP scaffolds strongly induced
as catecholamines and amines—to the material surface osteogenic differentiation, as indicated by ALP activity
via covalent bonds, thereby improving hydrophilicity, and staining results. In addition, qRT-PCR revealed that
adhesion, and biocompatibility. 54–56 As displayed in after co-culturing BMSCs with the three scaffold groups
Figure 4B1 and B2, the PSBP scaffolds featured better under osteogenic induction conditions, the expression
hydrophilicity after the addition of SrBG and PDA, of osteogenesis-related genes (COL1, ALP, and RUNX2)
providing more favorable conditions for cell adhesion was significantly upregulated in the PSBP scaffold group
and proliferation. Zhao et al. reported that SrBG compared to the P and SBP scaffold groups (Figure 7B).
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effectively improved the mechanical properties and bone This observation was consistent with the ALP activity and
repair capability of calcium aluminate cement. In terms staining results.
of mechanical properties, the compressive strength and
modulus of the PSBP scaffolds were significantly higher The immune microenvironment plays a crucial role in
than those of the P and SBP scaffolds, likely associated with bone repair, and MP phenotypic switching is critical for
the addition of SrBG and PDA. This suggests that the PSBP bone defect repair. To regulate the microenvironment’s
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Volume 11 Issue 4 (2025) 369 doi: 10.36922/IJB025210211