Vascularization is essential for the regeneration of three-dimensional (3D) bioprinting organs. As a general method to produce microfluidic channels in 3D printing constructs, coaxial extrusion has attracted great attention. However, the biocompatible bioinks are very limited for coaxial extrusion to fabricate microchannels with regular structure and enough mechanical properties. Herein, a hybrid bioink composed of alginate (Alg) and silk fibroin (SF) was proposed for 3D bioprinting of microchannel networks based on coaxial extrusion. The rheological properties of the bioink demonstrated that the hybrid Alg/SF bioink exhibited improved viscosity and shear thinning behavior compared with either pure Alg or SF bioink and had similar storage and loss modulus in a wide range of shear frequency, indicating a sound printability. Using a coaxial extrusion system with calcium ions and Pluronic F127 flowing through the core nozzle as cross-linkers, the Alg/SF bioink could be extruded and deposited to form a 3D scaffold with interconnected microchannels. The regular structure and smooth pore wall of microchannels inside the scaffold were demonstrated by optical coherence tomography. Micropores left by the rinse of F127 were observed by scanning electron microscope, constituting a hierarchical structure together with the microchannels and printed macropores. Fourier transform infrared spectroscopy analysis proved the complete rinse of F127 and the formation of β-sheet SF structure. Thus, Alg/SF could form a double cross-linked network, which was much stronger than the pure Alg network. Moreover, cells in the Alg/SF scaffold showed higher viability and proliferation rate than in the Alg scaffold. Therefore, Alg/SF is a promising bioink for coaxial extrusion-based 3D bioprinting, with the printed microchannel network beneficial for complex tissue and organ regeneration.

中文翻译：

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藻酸盐和丝素蛋白双交联网络可灌注分层微通道的三维生物打印

血管化对于三维 (3D) 生物打印器官的再生至关重要。作为在 3D 打印结构中生产微流体通道的通用方法，同轴挤压引起了极大的关注。然而，生物相容性生物墨水对于同轴挤压制造具有规则结构和足够机械性能的微通道非常有限。在此，提出了一种由藻酸盐 (Alg) 和丝素蛋白 (SF) 组成的混合生物墨水，用于基于同轴挤压的微通道网络的 3D 生物打印。生物墨水的流变特性表明，与纯 Alg 或 SF 生物墨水相比，混合 Alg/SF 生物墨水表现出改善的粘度和剪切稀化行为，并且在广泛的剪切频率范围内具有相似的储能和损耗模量，表明良好的印刷适性。使用钙离子和 Pluronic F127 流经核心喷嘴作为交联剂的同轴挤压系统，可以挤压和沉积 Alg/SF 生物墨水以形成具有互连微通道的 3D 支架。光学相干断层扫描显示了支架内部微通道的规则结构和光滑的孔壁。扫描电镜观察F127漂洗后留下的微孔，与微通道和印制大孔共同构成层次结构。傅立叶变换红外光谱分析证明了F127的完全漂洗和β-折叠SF结构的形成。因此，Alg/SF 可以形成双交联网络，比纯 Alg 网络强得多。而且，Alg/SF 支架中的细胞比 Alg 支架中的细胞显示出更高的活力和增殖率。因此，Alg/SF 是一种很有前途的生物墨水，可用于基于同轴挤压的 3D 生物打印，打印的微通道网络有利于复杂组织和器官的再生。