For extrusion-based bioprinting, the inks must be printable and rapidly present sufficient mechanical properties to support additional layers and provide a cohesive, manipulable structure. Thermosensitive hydrogels may be interesting candidates. However, the use of these materials is particularly challenging, since their rheological properties evolve with time and temperature. In this work, a rheological approach to characterize the printability of chitosan-based thermosensitive inks was developed. The method consists of evaluating: (1) the gelation kinetic at room temperature and at 37 C; (2) shear-thinning behavior to estimate the shear rate applied during printing as a function of printing parameters; and (3) the viscosity after shear removal (recovery test) to simulate behaviour after biomaterial deposition. Hydrogels containing 2 and 3% w v⁻¹ chitosan, combined with different gelling agents (sodium hydrogen carbonate (SHC), phosphate buffer, beta-glycerophosphate (BGP)) were tested, and compared with alginate/gelatin bioink as controls. To correlate the rheological studies with real printing conditions, a 3D-Discovery bioprinter was used to print hydrogels and the visual aspect of the printed structure was observed. Unconfined compressive tests were carried out to study the impact of applied shear rate during printing on the mechanical properties of printed structures. All pre-hydrogel solutions presented shear-thinning properties. The recovery of viscosity was found to depend on the hydrogel formulation, as well as the level of shear rate and the state of gelation at the time of printing. Formulations made with SHC and phosphate buffer presented too rapid gelation and phase separation, leading to poor printing results. One particularly promising formulation composed of SHC and BGP, when printed at a shear rate of 140 s⁻¹, before its gelation time (t _g ⩽ 15 min), resulted in good printability and 3D structures with rigidity comparable with the alginate/gelatin bioink. The methodology introduced in this paper could be used to evaluate the printability of other time- and temperature-dependent biomaterial inks in the future.

对于基于挤出的生物打印，墨水必须是可打印的，并能迅速呈现出足够的机械性能来支撑额外的层并提供有凝聚力的、可操作的结构。热敏水凝胶可能是有趣的候选者。然而，这些材料的使用特别具有挑战性，因为它们的流变特性会随着时间和温度而变化。在这项工作中，开发了一种表征壳聚糖基热敏油墨可印刷性的流变方法。该方法包括评估： (1) 在室温和 37°C 下的凝胶动力学；(2) 剪切变稀行为，以估计在打印过程中应用的剪切速率作为打印参数的函数；(3) 剪切去除后的粘度（恢复测试）以模拟生物材料沉积后的行为。含有 2% 和 3% wv 的水凝胶^-1测试了壳聚糖与不同胶凝剂（碳酸氢钠 (SHC)、磷酸盐缓冲液、β-甘油磷酸盐 (BGP)）的组合，并与作为对照的藻酸盐/明胶生物墨水进行了比较。为了将流变学研究与真实打印条件相关联，使用 3D-Discovery 生物打印机打印水凝胶，并观察打印结构的视觉方面。进行无侧限压缩试验以研究在打印过程中施加的剪切速率对打印结构的机械性能的影响。所有预水凝胶溶液均呈现剪切稀化特性。发现粘度的恢复取决于水凝胶配方，以及剪切速率的水平和印刷时的凝胶状态。用 SHC 和磷酸盐缓冲液制成的配方呈现过快的凝胶化和相分离，导致印刷效果不佳。一种由 SHC 和 BGP 组成的特别有前途的配方，当以 140 秒的剪切速率打印时^-1，在其胶凝时间（t _g ⩽ 15 分钟）之前，产生了良好的可印刷性和 3D 结构，其刚性与藻酸盐/明胶生物墨水相当。本文介绍的方法可用于评估其他与时间和温度相关的生物材料墨水的可印刷性。