Page 147 - IJB-9-6

International Journal of Bioprinting 3D printed bioactive dressings for burn wound treatment

Figure 3. BBG improved the printing outcome, consistency, and Young’s modulus of 3D-printed dressings. (A) Photographs of the 3D-printed dressings.
Hydrogel–BBG20 dressings showed the finest mesh structure and best shape fidelity. (B) The Young’s modulus of the 3D-printed dressings, compared to
the normal unwounded skin. Both samples with BBG exhibited Young’s modulus in the range of normal skin (n = 5). The Young’s modulus of the normal
skin is adopted from [67,68] .

within alginate chains. The slight increase in O-H bonds at 29% and 62% after adding 10 and 20 w/v% BBG, respectively.
2901 and 1021 cm shows the increase in hydrogen bonds BBG improved the stability of the hydrogel by increasing
−1
and interactions between water molecules and ions released the degradation time from 10 to 14 days. It can result from
from BBG. The appearance of peaks at 1630 cm can be (i) stronger electrostatic interactions, including hydrogen
−1
attributed to the reactions between proton donator groups bonds and van der Waals bonds between BBG and hydrogel
in gelatin amide groups and the cations released from chains and (ii) covalent crosslinks between alginate chains
BBG. The formation of intermolecular hydrogen bonds in the presence of ions released from BBG. As illustrated in
between water molecules, ions, and different overlapping Figure 1, adding BBG decreased the free volume within the
functional groups in gelatin and alginate makes a favorable hydrogel network, increasing the density and decreasing the
entanglement for enhanced mechanical behavior at certain samples’ permeability. The crosslinking process of sodium–
ratios of hydrogel:BBG. In the same line with mechanical alginate results from Na–Ca replacement and formation
testing results, forming covalent crosslinks between of the egg-box structure. Since each Ca ion can bond to
2+
bivalent ions and guluronic acid blocks in alginate results two carboxylate groups, the ions can crosslink the polymer
in lower permeability and higher mechanical stiffness in chains, which results in the formation of an insoluble,
samples with higher BBG content. Lower permeability gel-like substance. This is associated with the presence of
reduces the transport of water molecules and maintains guluronic acid blocks, as shown in Figure 4.
the structural integrity and stability of the hydrogel over
time. The higher degree of crosslinking between alginate 3.4. Hydration activity and water release kinetics
and BBG content can slow down the release of water which We studied the water content and water donation ability of
is desired for treatment of burn wounds. the 3D-printed dressings to predict their functionality for
clinical burn wound treatment. The initial water content
3.3. Degradation rate and stability slightly decreased by adding BBG content, as 3D-printed
The swelling/weight change and degradation rate of the hydrogel, hydrogel–BBG10, and hydrogel–BBG20
3D-printed dressing are shown in Figure 5. The addition of dressings showed 94.36 ± 0.29, 94.01 ± 0.09, and 93.71
BBG has negligible influences on the hydrogels and swelling ± 0.24% water content, respectively. Figure 6 depicts the
capacity, while the 10-day degradation rate decreased by 10-day water release from the dressings on ethylcellulose

Volume 9 Issue 6 (2023) 139 https://doi.org/10.36922/ijb.0118