Page 146 - IJB-9-6

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

Table 1. Qualitative histological grading criteria adopted from Altavilla et al. [65]
Score Re-epithelialization Dermal regeneration Granulation tissue formation
0 No epidermal organization No dermal organization Very thin or no granular layer

1 Very little epidermal organization Very little dermal organization Thin granulation layer
2 Little epidermal organization Little dermal organization Moderate granulation layer
3 Moderate epidermal organization Moderate dermal organization Thick granular layer
4 Complete remodeling of the epidermis Complete remodeling of dermis Very thick granular layer

This statistical test enables the evaluation of overall the hydrogel network result in higher mechanical strength
group differences and determines if there are significant and lower permeability. By increasing the amount of BBG
differences between the means of these groups. Following from 0 to 10 and 20 w/v%, Young’s modulus increased by
the ANOVA, the Student’s t-test is performed for pairwise 39% and 105%, respectively.
comparisons between specific groups. This test allows for
the determination of statistically significant differences 3.2. Chemical structure
between the means of two groups. Significance was set Typically, the hydrogel-based bioinks provide favorable
at the P-value <0.05. Statistical analyses were performed permeability to oxygen and nutrients. In order to evaluate
using GraphPad Prism 9. the interactions between the gelatin, alginate, and BBG
particulates, the chemical structure of the samples was
3. Results and discussion studied by FTIR spectroscopy, and the resulting spectra
are presented in Figure 4. Alginate and gelatin have
3.1. Mechanical properties overlapping carboxylate groups and hydroxyl groups
The 3D-printed hydrogel–BBG dressings were fabricated with 3200–3500 cm characteristic peaks, which is also
-1
using extrusion-based 3D printing technology with overlapping with O-H stretching bonds in water. The
different percentages of BBG content. Figure 3 shows amide I, II, and III bonds in gelatin and C=O bond as the
the appearance and Young’s modulus of the 3D-printed characteristic bond of alginate were observed in all samples
dressings after crosslinking with calcium ions. Traditionally, at a narrow peak at 1659–1243 cm bands . By increasing
[16]
−1
mechanical properties, such as bone scaffolds, are the BBG content, the intensity of hydrogen bonds
considered key characteristics for load-bearing tissue decreases due to the formation of crosslinks that show
engineering scaffolds. However, the mechanical behavior the hydroxyl groups in alginate are involved in crosslinks
of skin substitutes and wound dressings has become with divalent metals instead of hydrogen bonds. It can be
an increasingly important focus of preclinical studies. a result of the interactions between bivalent metals (e.g.,
Mechanical properties can significantly impact the Ca , Mg , Cu , Zn ) released from BBG and alginate
2+
2+
2+
2+
performance and clinical outcomes of these products, and the formation of crosslinks . Bands associated with
[69]
including level of pain and trauma experienced during alginate showed significant changes by adding BBG. The
application, coverage, and removal. In order to promote bands associated with guluronic acid groups appeared
moist wound healing, the dressings are required to exhibit between 500–450 cm and 821 cm were increased by
−1
−1
adequate mechanical properties to integrate with the BBG content, which shows the formation of =C-H groups.
wound bed and surrounding tissue, while simultaneously By increasing the BBG content, peaks associated with B-O
providing effective coverage against external pathogens and B-O appeared at 1402 cm band [70,71] , which increased
−1
3
and traumas. Also, dressings should exhibit elasticity in the in hydrogel–BBG20 compared to hydrogel–BBG10. The
range of surrounding skin to support the body movement peaks associated with metallic oxides within BBG, such as
and normal activities without pain and falling apart . The Ca-O, Mn-O, Cu-O, and Zn-O, appeared at 1000–600 cm
−1
[66]
Young’s modulus (E) of normal skin fluctuates between bands [72-76] . The C-O-C stretching bonds at 1080–1030 cm
−1
0.42 MPa and 0.85 MPa and has the highest value of and C=O bonds at 1621 cm in guluronic acid increased
−1
[67]
approximately 1 MPa . The tensile testing results from by BBG, which confirms the formation of crosslinks in
[68]
this work strongly support the positive effect of BBG on the alginate in the presence of ions released from BBG .
[69]
elasticity of the 3D-printed dressings: (i) stronger chemical The C-H stretching bands at 2600 cm slightly appeared
−1
bonds between BBG particles and alginate chains and (ii) in hydrogel–BBG10 and increased in hydrogel–BBG20,
reinforcement of hydrogel network with BBG particles. It confirming the interactions between ions released from
is generally accepted that the stronger chemical bonds in BBG and gelatin chains, and the formation of crosslinks
Volume 9 Issue 6 (2023) 138 https://doi.org/10.36922/ijb.0118