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International Journal of Bioprinting Extrusion-based biomaterial inks

Figure 3. Common crosslinking methods and principles in extrusion-based printing. (a) Temperature-dependent crosslinking; (b) photocrosslinking;
(c) reagent AB crosslinking; (d) self-assembly polymerization; (e) combinatory type; (f-j) examples of different crosslinking methods. (f) Printing dECM
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with different temperatures, reproduced under terms of the CC-BY license , copyright 2017, The Authors, published by Springer Nature. (g) Photo-
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crosslinking effects before, during and after printing, adapted with permission from © 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim .
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(h) Printing alginate with CaCl crosslinking , adapted with permission from 2015 Elsevier Ltd . (i) Self-supporting printing with nanoclay, adapted with
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permission from © 2017 American Chemical Society . (j) Printing alginate/GelMA/PEGOA with CaCl crosslinking and photocrosslinking, adapted
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with permission from © 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim .
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as poly (ethylene glycol) diacrylate (PEGDA), refer to directly self-supporting printed without environment
the biomaterial inks that require a certain intensity of limitation. In the combinatory type, biomaterial inks can
light to form a crosslinked hydrogel under the action of be processed using two or more gel crosslinking methods.
a photoinitiator . Reagent AB crosslinked type means For instance, biomaterial inks containing 1% alginate
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that the biological material reagent A needs to be added (w/v), 7% gelatin (w/v), and 5% Matrigel (v/v) pre-
to reagent B before it can form an ionically crosslinked heated at 37°C were moved to cartridge for maintaining
hydrogel or covalently crosslinked hydrogel. The action 35 minutes at room temperature to induce gelation in
time and concentration of reagent B will affect the order to increase the yield stress . The printed constructs
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solidification formability gel. For example, partially were soaked in 100 mM CaCl for 1 minute to maintain the
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crosslinked alginate hydrogel was printed above the structure for prolonged incubation. It should be reminded
crosslinking reagent , and the suitable ratio of alginate that the corresponding hydrogel crosslinking method
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to CaCl was 10:1 (w/w) to achieve suitable mechanical should be selected to meet the printability requirement
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rigidity with best printing quality. The self-assembly of the biomaterial inks according to the performance of
polymer, such as nanoclay and nanocellulose, can be bioprinter and experimental requirements.
Volume 9 Issue 2 (2023) 5 https://doi.org/10.18063/ijb.v9i2.649