Temirel Mikail, Dabbagh Sajjad Rahmani, Tasoglu Savas
Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA.
Mechanical Engineering Department, School of Engineering, Abdullah Gul University, Kayseri 38080, Turkey.
J Funct Biomater. 2022 Nov 7;13(4):225. doi: 10.3390/jfb13040225.
Extrusion-based 3D bioprinting is a promising technique for fabricating multi-layered, complex biostructures, as it enables multi-material dispersion of bioinks with a straightforward procedure (particularly for users with limited additive manufacturing skills). Nonetheless, this method faces challenges in retaining the shape fidelity of the 3D-bioprinted structure, i.e., the collapse of filament (bioink) due to gravity and/or spreading of the bioink owing to the low viscosity, ultimately complicating the fabrication of multi-layered designs that can maintain the desired pore structure. While low viscosity is required to ensure a continuous flow of material (without clogging), a bioink should be viscous enough to retain its shape post-printing, highlighting the importance of bioink properties optimization. Here, two quantitative analyses are performed to evaluate shape fidelity. First, the filament collapse deformation is evaluated by printing different concentrations of alginate and its crosslinker (calcium chloride) by a co-axial nozzle over a platform to observe the overhanging deformation over time at two different ambient temperatures. In addition, a mathematical model is developed to estimate Young’s modulus and filament collapse over time. Second, the printability of alginate is improved by optimizing gelatin concentrations and analyzing the pore size area. In addition, the biocompatibility of proposed bioinks is evaluated with a cell viability test. The proposed bioink (3% w/v gelatin in 4% alginate) yielded a 98% normalized pore number (high shape fidelity) while maintaining >90% cell viability five days after being bioprinted. Integration of quantitative analysis/simulations and 3D printing facilitate the determination of the optimum composition and concentration of different elements of a bioink to prevent filament collapse or bioink spreading (post-printing), ultimately resulting in high shape fidelity (i.e., retaining the shape) and printing quality.
基于挤出的3D生物打印是一种用于制造多层复杂生物结构的有前途的技术，因为它能够通过简单的程序实现生物墨水的多材料分散（特别是对于增材制造技能有限的用户）。尽管如此，该方法在保持3D生物打印结构的形状保真度方面面临挑战，即由于重力导致细丝（生物墨水）坍塌和/或由于低粘度导致生物墨水扩散，最终使能够维持所需孔隙结构的多层设计的制造变得复杂。虽然需要低粘度以确保材料的连续流动（不堵塞），但生物墨水应具有足够的粘性以在打印后保持其形状，这突出了生物墨水性能优化的重要性。在这里，进行了两项定量分析以评估形状保真度。首先，通过在平台上使用同轴喷嘴打印不同浓度的藻酸盐及其交联剂（氯化钙）来评估细丝坍塌变形，以观察在两种不同环境温度下随时间的悬垂变形。此外，还开发了一个数学模型来估计杨氏模量和细丝随时间的坍塌。其次，通过优化明胶浓度和分析孔径面积来提高藻酸盐的可打印性。此外，通过细胞活力测试评估所提出的生物墨水的生物相容性。所提出的生物墨水（4%藻酸盐中含3% w/v明胶）在生物打印五天后产生了98%的归一化孔数（高形状保真度），同时保持了>90%的细胞活力。定量分析/模拟与3D打印的结合有助于确定生物墨水不同成分的最佳组成和浓度，以防止细丝坍塌或生物墨水扩散（打印后），最终实现高形状保真度（即保持形状）和打印质量。
