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Fayyazbakhsh, et al.
A

B C

Figure 9. (A) Swelling capacity and degradation of the 3D-printed dressings (n = 3). (B) One-week degradation rate of 3D-printed dressings
(n = 3). Samples with higher gelatin content showed a faster degradation rate and higher swelling capacity. All samples could stay in PBS
for at least 7 days (168 h). The G6-A2 dressings with the highest gelatin content showed significantly faster degradation (P < 0.05), which
means that the permeability of this sample is higher than the other samples. (C) Total water content and hydration activity of the gelatin-
alginate 3D-printed dressing on a super-absorbent surface to simulate dry burn wound surface (n = 3, P < 0.05). The higher permeability in
this sample justifies its faster degradation and higher water donation.

wound care products, as it is favorable for wound wound surface and prolonged healing that increase the
dressings to stay on the wound for 3 – 7 days to reduce the infection risk and chronic wound incidence. Accordingly,
pain and discomfort to the patient, risk of infection, the the G6-A2 dressing with relatively higher gelatin content
trauma caused by dressing removal, and cost. All samples and adequate degradation rate will support burn wound
showed up to 7 days of persistence in PBS, which predicts healing more efficiently compared to the other samples.
the long-lasting persistence of the proposed dressings on We studied the water content and water donation
the wounds. As shown in Figure 9B, the degradation ability of the 3D-printed dressings to predict their hydration
rate in the 3D-printed dressing decreased by increasing activity for clinical burn wound healing. Figure 9C depicts
the alginate concentration, which confirms the prolonged the total water content and overnight water donation
degradation of G0-A8 and G2-A6 due to the higher of the dressings on ethylcellulose substrate as a super-
covalent cross-links in these samples. The results from absorbent surface representing the dehydrated surface
swelling and degradation rate support the clinical stability of burn wounds. The water content slightly increased by
of all dressings for 1-week wound coverage. The G6-A2 gelatin concentration, as G6-A2 dressings showed 94.3
dressings showed the fastest and highest degradation ± 2.9% water content. Furthermore, by increasing the
associated with the acidic residues of the gelatin chain gelatin concentration, hydration activity is increased after
during the degradation, which can also accelerate the overnight exposure to the ethylcellulose membrane as a
degradation of alginate chains. Furthermore, as shown in burn wound model, which is due to the (i) lower degree
Figure 9A and B, the faster degradation rate and higher of cross-linking, (ii) weaker chemical bonds, (iii) higher
swelling capacity in G6-A2 dressing are associated with permeability, and (iv) lower molecular weight of gelatin
higher interaction with water molecules, which is a key network compared to alginate chains. This is consistent
factor for further biocompatibility. According to other with the higher swelling capacity and faster degradation
studies, an acidic environment helps wound healing rate in the G6-A2 dressing. Figures 8A and B show
by controlling wound infection, antimicrobial activity, the electrostatic interactions between the amide groups
protease activity, and oxygen release [48,49] . Notably, the of gelatin and the carboxylate and hydroxyl groups
dressing samples with prolonged degradation that remains of alginate, which are associated with the increased
longer than 7 days on the wound are not recommended physical entanglement and the reduced free volume in
for burn wound healing due to the lower interactions with the hydrogel mixture network, particularly in the G6-A2

International Journal of Bioprinting (2022)–Volume 8, Issue 4 283