Page 117 - IJB-9-2

International Journal of Bioprinting Photocurable pullulan-based bioink for 3D printing

Figure 3. FTIR spectra of pullulan and Pul-NB.

Figure 4. Pul-NB-based solutions with different degree of substitution (A) and different solid content (B) before and after UV irradiation.

the hydroxyl (-OH) groups of pullulan molecular chains. NB 1 could not turn into hydrogel due to the excessively
This peak was blue-shifting in the FTIR spectrum of Pul- low DS. Pul-NB 2, Pul-NB 3, and Pul-NB 4 could quickly
NB. The three typical peaks at the wave numbers 928, 848, form stable hydrogels through photopolymerization under
and 754 cm were the characteristic absorption peaks of the UV irradiation for 10 s. From the photos in Figure 4B, the
-1
glucopyran ring, corresponding to α-1,6 glycosidic bonds, stable hydrogels were all formed using 6%, 7%, 8%, and
α-configuration, and α-1,4 glycosidic bonds . Along with 10% (w/v) Pul-NB-based solution through UV irradiation.
[34]
absorption peaks attributed to pullulan, FTIR spectrum The stability of Pul-NB hydrogels was improved with the
of Pul-NB shows an extra peak at 1724 cm , which was increase of Pul-NB content.
-1
characteristic of the stretching vibration of carbonyl To study the role of crosslinkers in the formation of
groups of norbornene moieties. FTIR spectroscopy of Pul- the hydrogels, both HDT and DTT were used for light-
NB further confirmed the presence of norbornene groups curing processing as the thiols crosslinkers. It could be seen
on pullulan chains. in Figure S1 that the Pul-NB cross-linked by HDT also
3.2 Formation of Pul-NB hydrogels formed hydrogels by UV irradiation. However, the hydrogel
In order to observe the ability of synthesized Pul-NB with was non-transparent milky-white, which is due to the poor
different DS to form hydrogels, the Pul-NB solution added solubility of HDT in water. Considering that HDT used for
with LAP and DTT was photographed before and after UV thiol-ene chemistry may cause uneven gelation, DTT is the
irradiation. It could be seen from Figure 4A that the Pul- preferred thiols crosslinker for light-curing gelation.

Volume 9 Issue 2 (2023) 109 https://doi.org/10.18063/ijb.v9i2.657