Cui Yuecheng, Jin Ronghua, Zhang Yifan, Yu Meirong, Zhou Yang, Wang Li-Qun
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China.
Second Affiliated Hospital of Medical College, Zhejiang University, Hangzhou 310009, P. R. China.
Int J Bioprint. 2021 Aug 27;7(4):397. doi: 10.18063/ijb.v7i4.397. eCollection 2021.
The hydrogel formed by polyethylene glycol-aliphatic polyester block copolymers is an ideal bioink and biomaterial ink for three-dimensional (3D) bioprinting because of its unique temperature sensitivity, mild gelation process, good biocompatibility, and biodegradability. However, the gel forming mechanism based only on hydrophilic-hydrophobic interaction renders the stability and mechanical strength of the formed hydrogels insufficient, and cannot meet the requirements of extrusion 3D printing. In this study, cellulose nanocrystals (CNC), which is a kind of rigid, hydrophilic, and biocompatible nanomaterial, were introduced to enhance the hydrogels so as to meet the requirements of extrusion 3D printing. First, a series of poly(-caprolactone/lactide)--poly(ethylene glycol)--poly(-caprolactone/lactide) (PCLA-PEG-PCLA) triblock copolymers with different molecular weights were prepared. The thermodynamic and rheological properties of CNC-enhanced hydrogels were investigated. The results showed that the addition of CNC significantly improved the thermal stability and mechanical properties of the hydrogels, and within a certain range, the enhancement effect was directly proportional to the concentration of CNC. More importantly, the PCLA-PEG-PCLA hydrogels enhanced by CNC could be extruded and printed through temperature regulation. The printed objects had high resolution and fidelity with effectively maintained structure. Moreover, the hydrogels have good biocompatibility with a high cell viability. Therefore, this is a simple and effective strategy. The addition of the hydrophilic rigid nanoparticles such as CNC improves the mechanical properties of the soft hydrogels which made it able to meet the requirements of 3D bioprinting.
聚乙二醇-脂肪族聚酯嵌段共聚物形成的水凝胶因其独特的温度敏感性、温和的凝胶化过程、良好的生物相容性和生物降解性，是用于三维（3D）生物打印的理想生物墨水和生物材料墨水。然而，仅基于亲水-疏水相互作用的凝胶形成机制使得所形成水凝胶的稳定性和机械强度不足，无法满足挤出式3D打印的要求。在本研究中，引入了一种刚性、亲水性且具有生物相容性的纳米材料——纤维素纳米晶体（CNC）来增强水凝胶，以满足挤出式3D打印的要求。首先，制备了一系列不同分子量的聚（ε-己内酯/丙交酯）-聚（乙二醇）-聚（ε-己内酯/丙交酯）（PCLA-PEG-PCLA）三嵌段共聚物。研究了CNC增强水凝胶的热力学和流变学性质。结果表明，CNC的加入显著提高了水凝胶的热稳定性和机械性能，并且在一定范围内，增强效果与CNC的浓度成正比。更重要的是，经CNC增强的PCLA-PEG-PCLA水凝胶可通过温度调节进行挤出和打印。打印出的物体具有高分辨率和保真度，结构得到有效保持。此外，该水凝胶具有良好的生物相容性和高细胞活力。因此，这是一种简单有效的策略。添加如CNC这样的亲水性刚性纳米颗粒可改善柔软水凝胶的机械性能，使其能够满足3D生物打印的要求。
