The emergence of 3D bioprinting is expected to solve the present puzzle in the field of regenerative medicine. However, the appropriate bioink was lacking due to the rigorous requirement of high printability and biocompatibility, which was often contradictory. In this study, a novel thixotropic magnesium phosphate-based gel (TMP-BG) was prepared and its application in 3D printing was explored. The stable gel could be synthesized by adjusting the ratio of ternary reactants (NaOH, Mg(OH)₂, and H₃PO₄). Moreover, the structure, morphology, particle size and composition of TMP-BG were characterized. Furthermore, the rheological and thixotropic behaviors and degradation of TMP-BG were investigated. The printability of TMP-BG was tested by using the extrusion-based 3D printer. The biocompatibility of TMP-BG was evaluated in vitro. The composition of TMP-BG was MgNa₃H(PO₄)₂, which was of nanometer and sub-micro scale and easily formed a complex three-dimensional porous structure. Rheological results showed that the gel had notable shear thinning behavior and good thixotropy, which could provide the TMP-BG with injectability and formability simultaneously. In addition, the thixotropic mechanisms of TMP-BG were speculated to be a model of “house of cards”. Finally, TMP-BG could be printed into large-sized and different complex three-dimensional structures. Results of the MG-63 cell viability and cell proliferation confirmed the biocompatibility of TMG-BG. The present newly developed TMP-BG has the potential to be used as 3D printing bioink involving living cells for future applications in regenerative medicine.

中文翻译：

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一种新颖的触变性磷酸镁基生物墨水，具有出色的可印性，可用于3D打印

预计3D生物打印的出现将解决再生医学领域的当前难题。然而，由于对高可印刷性和生物相容性的严格要求而缺乏合适的生物墨水，这常常是矛盾的。在这项研究中，制备了新型的触变磷酸镁基凝胶（TMP-BG），并探索了其在3D打印中的应用。可以通过调节三元反应物（NaOH，Mg（OH）₂和H ₃ PO ₄）的比例来合成稳定的凝胶。）。此外，表征了TMP-BG的结构，形态，粒径和组成。此外，研究了TMP-BG的流变和触变行为以及降解情况。使用基于挤压的3D打印机测试了TMP-BG的可打印性。在体外评估了TMP-BG的生物相容性。TMP-BG的组成为MgNa ₃ H（PO ₄）₂具有纳米和亚微米级，并且容易形成复杂的三维多孔结构。流变学结果表明该凝胶具有显着的剪切稀化行为和良好的触变性，可以同时为TMP-BG提供可注射性和可成型性。此外，TMP-BG的触变机理被认为是“纸牌屋”的模型。最后，TMP-BG可以打印成大型且不同的复杂三维结构。MG-63细胞活力和细胞增殖的结果证实了TMG-BG的生物相容性。当前新开发的TMP-BG有潜力用作涉及活细胞的3D打印生物墨水，以用于未来在再生医学中的应用。