Meniscal injury is more likely to cause a permanent alteration of the biomechanical and biological environment of the knee joint, mainly due to the morphological mismatch and substantial loss of meniscal tissues. Herein, to overcome this challenge, we developed an improved bioink with enhanced printability, while maintaining the biocompatibility of major cellular component of the meniscus, namely fibrochondrocytes. Firstly, cellulose nanofiber (CNF) was mixed with gelatin-alginate thermal-responsive bioinks to improve the printability. Afterward, individual-specific meniscal prototypes based on the 3D reconstruction of MRI data were bioprinted using our bioink. The rheological and printability properties of the bioinks were characterized to select proper bioink content and bioprinting parameters. And then, a series of biological characterizations of the bioprinted samples, such as cell viability, metabolic activity, and extracellular matrix accumulation, were carried out in vitro. The results indicated that superior rheological performance and printability of CNF-modified bioink were achieved, ensuring high-precision bioprinting of specific-designed meniscal prototype when compared with the non-CNF-containing counterparts. Meanwhile, biological tests indicated that fibrochondrocytes encapsulated within the CNF-modified bioink maintained long-term cellular viability as well as acceptable extracellular matrix accumulation. This study demonstrates that the CNF-modified bioink is in favor of the printing fidelity of specific meniscus by improved rheological properties, minimizing the mismatch between artificial meniscal implants and native knee joint tissues, thereby permitting the evolution of clinical therapeutic methods of meniscal reconstruction.

中文翻译：

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纤维素纳米纤维修饰明胶-藻酸盐生物油墨的可印刷性优化，用于潜在的弯月面生物印刷

半月板损伤更可能引起膝关节生物力学和生物环境的永久改变，这主要是由于形态不匹配和半月板组织的大量损失。在本文中，为了克服这一挑战，我们开发了一种改进的生物墨水，该墨水具有增强的可印刷性，同时又保持了弯月面主要细胞成分（即纤维软骨细胞）的生物相容性。首先，将纤维素纳米纤维（CNF）与明胶-藻酸盐热响应性生物油墨混合以改善可印刷性。然后，使用我们的bioink对基于MRI数据的3D重建的特定个体半月板原型进行生物打印。表征生物油墨的流变学和可印刷性，以选择合适的生物油墨含量和生物印刷参数。然后，在体外对生物打印样品进行了一系列生物学表征，例如细胞活力，代谢活性和细胞外基质积累。结果表明，与不含CNF的同类油墨相比，CNF改性的生物油墨具有优异的流变性能和可印刷性，可确保特定设计的半月板原型的高精度生物印刷。同时，生物学测试表明，封装在CNF修饰的生物墨水中的纤维软骨细胞保持了长期的细胞生存能力以及可接受的细胞外基质积累。这项研究表明，CNF修饰的生物墨水通过改善流变特性，有利于特定弯月面的印刷保真度，