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International Journal of Bioprinting Bioprinting of DNA hydrogels for bone organoids

Figure 2. Light-based DNA hydrogels. (A) Light-based DNA hydrogels. Reprinted with permission from Kang H, Liu H, Zhang X, et al., 2011, Photorespon-
sive DNA-cross-linked hydrogels for controllable release and cancer therapy. Langmuir, 27(1):399–408. Copyright 2010. American Chemical Society .
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(B) DNA hydrogels are induced by light with macro scopic volume change. Reprinted with permission from Peng L, You M, Yuan Q, et al., 2012, Macro-
scopic volume change of dynamic hydrogels induced by reversible DNA hybridization J Am Chem Soc, 134(29):12302–12307. Copyright 2012. American
Chemical Society . (C) Reversible gel–sol transition of light-based DNA hydrogels. Adapted with permission from Kandatsu D, Cervantes-Salguero K,
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Kawamata I, et al., ChemBioChem, Copyright © 1999-2023 John Wiley & Sons .
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DNA under UV irradiation, which consequently causes of the stick ends. Accordingly, other light-based hydrogels
a phase transition from gel to sol. The process could be conferred with multiple functions can also be synthesized
used for the adjustable release of drugs and cancer therapy by the reasonable designation of different light-based
due to its inherent reversible property. Based on the light- artificial bases.
reversible DNA hybridization, another study designed Although light-based DNA hydrogel has been fabricated
a dynamic hydrogel with macroscopic volume changes successfully, 3D bioprinting of the hydrogel has never been
as shown in Figure 2B. The hydrogels were synthesized put into practice. However, several reports demonstrated
using polyacrylamide in combination with azobenzene- the bioprintability of the hydrogel. Li et al. prepared a
modified DNA strands and their complementary strands. supramolecular polypeptide–DNA hydrogel and adopted
The two DNA strands resulted in shrinkage of the hydrogel in situ multilayer 3D bioprinting for the first time . Desired
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through hybridization and formation of a duplex structure structures can be printed through alternative deposition of
under visible light. Other light-based molecules have two complementary bioinks. The printed DNA hydrogels
also been introduced to fabricate DNA-based hydrogels. are geometrically uniform without boundaries and can
Stimuli-based DNA hydrogels underwent a sol–gel keep their shapes up to the millimeter scale without
phase transformation under UV irradiation at various collapse, which is attributed to their healing properties
wavelengths . This hydrogel is achieved by hybridizing the and high mechanical strengths. The same researchers also
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sticky ends of an X-shaped DNA motif. Additionally, as an demonstrated that the hydrogel is an ideal biomaterial for
artificial base, 3-cyanovinylcarbazole (CNVK) is capable of 3D bioprinting to produce designable 3D constructs for
reacting with thymine at 366 nm and dissociating at 340 nm applications in tissue engineering . Additionally, another
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of UV irradiation (Figure 2C). Once the DNA sequence study reported low-cost 3D bioprinting of DNA hydrogels
is introduced to the hydrogel system, the repeated sol–gel based on a commercially available extrusion printer by
transitions could be achieved by reversible hybridization

Volume 9 Issue 2 (2023) 434 https://doi.org/10.18063/ijb.688