Page 143 - IJB-9-6

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

Figure 1. Schematic of the structure of gelatin, BBG, sodium alginate, and hydrogel–BBG blend. Gelatin and alginate are semi-interpenetrating networks
(semi-IPN), whereby the free volume decreases due to (i) the electrostatic interactions between BBG particulates and gelatin–alginate chains and (ii) the
formation of crosslinks between alginate chains.

gelatin, gelatin-BBG10, and gelatin-BBG20 solutions. A 10 2.4. Mechanical testing
w/v% stock solution of sodium alginate was prepared by The dog-bone-shaped dressings were tested for
dissolving 1000 mg of sodium alginate powder in 10 mL mechanical properties using the Universal Instron 5969
of DI water. To achieve a gelatin:alginate ratio of 5:3, 3 mL Dual Column Testing System (Instron, Massachusetts,
of the sodium alginate stock solution was added dropwise USA) and the BlueHill Universal Software (n = 5).
to the gelatin–BBG solutions and stirred at 800 rpm for 40 The scaffolds were assessed using a uniaxial tensile load
min at 40°C to obtain clear homogeneous compounds of frame at 5 mm/min, typical for polymer specimens to
hydrogel, hydrogel–BBG10, and hydrogel–BBG20 bioinks. measure the modulus of elasticity, yield strength, and
The schematic microstructure of gelatin, alginate, BBG, yield strain of the scaffolds in accordance with the ASTM
and their mixture is shown in Figure 1. F2150-8 standard.

2.3. 3D printing 2.5. Evaluation of chemical structure
In this research, extrusion-based 3D printing technology The chemical structures of the bioinks were identified
was utilized using the Inkredible® bioprinter (CELLINK using a Nicolet iS50 Fourier-transform infrared
Corporation, Sweden). The dressings were printed directly spectroscopy (FTIR) spectrophotometer (Thermo
onto sterile Petri dishes with the print head temperature Scientific, Massachusetts, USA) equipped with a diamond
adjusted at 25°C and 35°C for hydrogel and hydrogel– crystal cell of attenuated total reflection (ATR) accessory.
BBG bioinks, respectively. The dressings were printed at All the spectra were recorded at a resolution of 4 cm
−1
2.5 mm/s speed and 100 kPa pressure with a geometry with 32 scans with a data spacing of 0.482 cm in the
−1
3
of square (30 × 30 × 3 mm ) and dog bone (30 × 10 × 5 mid-infrared region (4000–400 cm ). The obtained
−1
mm ) for different tests. The 3D-printed dressings were spectra were analyzed with OMNIC 9.2.41 software
3
immersed in 0.2 M calcium nitride (CaNO ) solution for (Thermo Scientific, Massachusetts, USA). The infrared
3
10 min to form crosslinks between alginate chains. After (IR) spectrum data from Sigma Aldrich were used to
crosslinking, 3D-printed dressings were rinsed with DI identify characteristic chemical bonds in gelatin, alginate,
water three times and stored at 4°C. and water.
Volume 9 Issue 6 (2023) 135 https://doi.org/10.36922/ijb.0118