3D printing of chitosan hydrogels has attracted wide interest because of their excellent biocompatibility, antibacterial activities, biodegradability, zero toxicity and low cost. However, chitosan inks are often involved in toxic and organic solvents. Moreover, the recently reported 3D-printed chitosan scaffolds lack enough strength, thus limiting their use in tissue engineering. Here, we reported a chitosan ink obtained by dissolving chitosan into an alkali aqueous solution. This chitosan ink is a stable solution at low temperature (5 °C), but once heated, the chitosan chains self-assemble to lead to gelation. Based on this principle, a corresponding direct ink writing (DIW) method was developed to print high-strength chitosan hydrogels. Specifically, the chitosan ink was extruded into heated deionized water to complete the in situ gelation. The temperature of the nozzle and hot water was well controlled to keep the printing process stable. The rheological behavior of the chitosan ink was investigated and the printing parameters were systematically studied to print chitosan hydrogel scaffolds with high quality and high strength. Based on these, high-strength (2.31 MPa for compressive strength) and complex chitosan hydrogel structures can be directly printed. The cell culture and the wound healing results further show that the printed chitosan scaffolds with this method have great potential in tissue engineering.

中文翻译：

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无需任何有机溶剂的3D打印高强度壳聚糖水凝胶支架。

壳聚糖水凝胶的3D打印具有出色的生物相容性，抗菌活性，生物降解性，零毒性和低成本，因此引起了广泛的关注。但是，壳聚糖油墨通常与有毒和有机溶剂有关。而且，最近报道的3D打印的壳聚糖支架缺乏足够的强度，因此限制了它们在组织工程中的使用。在这里，我们报道了通过将壳聚糖溶解在碱性水溶液中而获得的壳聚糖油墨。这种壳聚糖墨水在低温（5°C）下是稳定的溶液，但是一旦加热，壳聚糖链就会自组装并导致凝胶化。基于此原理，开发了相应的直接墨水书写（DIW）方法来印刷高强度壳聚糖水凝胶。具体而言，将壳聚糖油墨挤出到加热的去离子水中以完成原位凝胶化。喷嘴和热水的温度得到了很好的控制，以保持打印过程的稳定。研究了壳聚糖油墨的流变行为，并系统地研究了印刷参数，以印刷高质量，高强度的壳聚糖水凝胶支架。基于这些，可以直接打印高强度（抗压强度为2.31 MPa）和复杂的壳聚糖水凝胶结构。细胞培养和伤口愈合结果进一步表明，用这种方法印刷的壳聚糖支架在组织工程中具有巨大的潜力。