Fabrication technique determines the physicochemical and biological properties of scaffold, including porosity, mechanical strength, osteoconductivity, and bone regenerative potential. Biphasic calcium phosphate (BCP)-based scaffolds are superior in bone tissue engineering due to their suitable physicochemical and biological properties. We developed an indirect selective laser sintering (SLS) printing strategy to fabricate 3D microporous BCP scaffolds for bone tissue engineering purposes. The green part of BCP scaffold was fabricated by SLS at relevantly low temperature in the presence of epoxy resin (EP) and the remaining EP was decomposed, and eliminated by a subsequent sintering process to obtain the microporous BCP scaffolds. Physicochemical properties, cell adhesion, biocompatibility, in vitro osteogenic potential and rabbit critical size cranial bone defect healing potential of the scaffolds were extensively evaluated. This indirect SLS printing eliminated the drawbacks of conventional direct SLS printing at high working temperatures, i.e., wavy deformation of the scaffold, hydroxyapatite decomposition, and conversion of β-TCP to α-TCP. Among the scaffolds printed with various binder ratios (by weight) of BCP and EP, the scaffold with 50/50 binder ratio (S4) showed the highest mechanical strength and porosity with the smallest pore size. Scaffold S4 showed the highest effect on osteogenic differentiation of precursor cells in vitro, and this effect was ERK1/2 signaling dependent. Scaffold S4 robustly promoted precursor cells homing, endogenous bone regeneration, and vascularization in rabbit critical-size cranial defect. In conclusion, BCP scaffold fabricated by indirect SLS printing maintains the physicochemical properties of BCP and possess the capacity to recruit host precursor cells to the defect site and promote the endogenous bone regeneration possibly via activation of ERK1/2 signaling.

中文翻译：

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间接选择性激光烧结印刷的微孔双相磷酸钙支架通过激活ERK1 / 2信号传导促进内源性骨再生。

制造技术决定了支架的物理化学和生物学特性，包括孔隙率，机械强度，骨传导性和骨再生潜力。基于双相磷酸钙（BCP）的支架由于其合适的理化和生物学特性而在骨组织工程中具有优势。我们开发了一种间接选择性激光烧结（SLS）打印策略，以制造用于骨组织工程目的的3D微孔BCP支架。BCP支架的生坯部分是通过SLS在相对较低的温度下在环氧树脂（EP）的存在下制造的，剩余的EP被分解，并通过随后的烧结工艺消除，从而获得了微孔BCP支架。理化性质，细胞粘附，生物相容性，广泛评估了支架的体外成骨潜力和兔临界尺寸颅骨缺损的愈合潜力。这种间接SLS印刷消除了在较高的工作温度下常规直接SLS印刷的缺点，即支架的波浪形变形，羟基磷灰石分解以及β-TCP转化为α-TCP。在以BCP和EP的各种粘合剂比率（按重量计）印刷的支架中，具有50/50粘合剂比率（S4）的支架表现出最高的机械强度和孔隙率，且孔径最小。支架S4在体外对前体细胞的成骨分化显示出最高的作用，并且这种作用是ERK1 / 2信号传导依赖性的。支架S4强烈促进兔临界大小颅骨缺损中的前体细胞归巢，内源性骨再生和血管形成。