Evaluation of bioink printability with quantitative methods to aid material development
June 5-9, 2017
During extrusion-based bioprinting, the deposited bioink filaments are subjected to deformations, such as collapse of overhanging filaments and fusion between adjacent filaments, which compromise shape fidelity of printed constructs. The degree of deformation of printed filaments could be used to quantitatively assess the printability of newly developed bioinks. This approach would be an alternative to current assessment through qualitative visual inspection after printing, which have been hampering any comparison between different bioinks. For this reason, we propose two quantitative printability tests based on the mentioned filament deformations: filament collapse of overhanging structures (Fig 1a) and filament fusion on parallel filaments (Fig 1b). Both printability tests were applied on two printable hydrogel platforms: poloxamer 407 and poly(ethylene glycol) blends (poloxamer/PEG), displaying a range of yield stress values. We also propose theoretical models for each test to predict printability from bioink yield stress. The results on poloxamer/PEG hydrogels show that as the yield stress decreases, the filament collapse is greater, decreasing the ability to maintain the shape of suspended filaments. Similarly, filament fusion occurs at bigger filament distances, decreasing resolution on the x-y plane. These results confirm that printability is largely dependent on yield stress. Our bioink printability testing is straightforward, assessible with any extrusion-based bioprinting system. The proposed method provides a quantitative evaluation based on physical deformation of printed filaments, potentially reducing long experimental trial-and-error printing with newly developed bioinks and allowing reproducible comparisons between different inks.
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Lotte Groen, Alexandre Ribeiro, Tina Vermonden, Wim Hennink, Maarten Blokzijl, Miguel Castilho, Jos Malda, and Riccardo Levato, "Evaluation of bioink printability with quantitative methods to aid material development" in "Biofabrication for Hierarchical in Vitro Tissue Models", Jürgen Groll (University of Würzburg, Germany) Jos Malda (University Medical Centre Utrecht, The Netherlands) Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/biofab_tissue_model/16