Page 449 - IJB-9-2

International Journal of Bioprinting Fabrication of 3D functional hydrogel for wound dressings

(0%, 0.5%, 1.0%, 1.5%w/v) of QCS were introduced into in section S2 of the Supplementary File. The lyophilized
the solution. The selection of the maximum concentration hydrogels (GADQ0%, GADQ0.5%, GADQ1.0%, and
of QCS is described in the section S1 of the Supplementary GADQ1.5%) were weighed as W . After soaking for a
0
File. The samples with different m QCS were named GAQ0%, specific time in phosphate-buffered saline (PBS, 20 mL) at
GAQ0.5%, GAQ1.0%, and GAQ1.5%, respectively, where 25°C, the excess water on the surface of the hydrogels was
“G” stands forgelatin, “A” stands for SA, and “Q” stands wiped with filter paper and weighed as W. The swelling
f
for QCS. ratio was calculated by the following formula :
[15]
2.4. Rheological properties of GAQ bioinks Swelling ratio () = W − W 0 ×100 % (II)
%
f
Characteristics of rheology of Gel/Alg/QCS (GAQ) bioinks W 0
with gradient rate were tested to evaluate their printability.
The parallel-plate rotational rheometer MCR 302 was used 2.8. Antioxidant capacity of the GADQ hydrogels
to test the temperature sensitivity, shear viscosity, and The antioxidant activity was evaluated by scavenging ability
viscoelasticity of the inks. For the temperature sensitivity of DPPH-free radicals. Four same size (10 mm × 10 mm ×
test, the temperature range was set as 10°C–40°C, the 2 mm) samples (GADQ0%, GADQ0.5%, GADQ1.0%, and
shear strain was 1%, and the frequency was 1 Hz. For shear GADQ1.5%) were soaked in centrifuge tubes containing
viscosity test, the shear rate ranged from 0.01 to 1000 1/s. 3 mL DPPH (0.1 mmol/L) absolute ethanol solution,
For viscoelastic test, the shear strain was set at 1%, and the respectively, following incubation in a shaker with a speed
angular frequency range was set at 0.01–100 rad/s. of 200 rpm at 25°C for 15 min. UV spectrophotometer
(UV-2600, Japan) was used to measure their absorbance
2.5 Fabrication of the GADQ 3D hydrogels value at 517 nm. The experimental groups were set as A ,
s
The bioprinter (Bio-Architect, Regenovo Biotechnology and the blank control group containing only DPPH was set
Co., Ltd.) was controlled at a speed of 10 mm/s and an as A . The elimination ratio of DPPH can be calculated as
0
extrusion pressure of 0.21 MPa, Operating with a 24G follows :
[47]
(0.31 mm) nozzle. The temperature of the printer nozzle

was controlled between 22°C and 25°C, and the platform Antioxidant ability (%) =1− A S   × 100% (III)

temperature was maintained at 8°C through the water  A 0 
cooler. The printing model was set as 30 mm × 10 mm × 2 mm
cuboid, and the filling distance was 0.8 mm. 2.9. Hemolysis test of the GADQ hydrogels
The collected fresh rat blood was centrifuged at 1000 rpm
The 3D-printed hydrogel scaffolds were immersed in
a 50 mmol/L EDC/NHS and 2%(w/v) CaCl crosslinking for 10 min, and diluted to 2 v/v% with normal saline.
Then, the diluted blood (5 mL) was co-cultured with these
2
agent solution, and 0.2% (W/V) dopamine was added onto four hydrogels (size 10 mm × 10 mm × 2 mm) for 1 h at
the crosslinked hydrogel network for 4 h. The hydrogels 37°C, respectively. One hour later, hydrogels were removed
were washed with deionized water to remove surface EDC/ with tweezers, and blood suspension was centrifuged at
NHS following freeze-drying, and then stored for later use.
1500 rpm for 15 min. The absorbance of the supernatants
2.6. Mechanical properties assay for the GADQ was read at 540 nm by a UV spectrometer. The group
hydrogels added with 0.1% Triton X-100 was set as the positive
The tensile properties of 3D-printed hydrogel scaffolds control and the one added with regular saline was assigned
were evaluated by a dynamic mechanics analyzer (Q800TA, as the negative control. The formula of hydrogel hemolysis
USA). The samples (30 mm × 10 mm × 2 mm) were fixed ratio is as follows:
in the drawing fixture. The drawing machine increased the  A − A 
tension with a speed of 1 N/min until the samples were Hemolysis (%) =  p b  ×100% (IV)
fractured. The stress(σ) and strain(ε) values were obtained  A − A b 
t
by the analyzer. The formula of tensile modulus is as follows: where A represents the absorbance value of samples,
p
A is the absorbance value of the Triton X-100 positive
E = σ/ε (I) control, and A is the absorbance value of normal saline.
t
The compression test is described in section S5 of the b
Supplementary File. 2.10. Antibacterial activity of the GADQ hydrogel
The GADQ hydrogel antibacterial activity was tested by
2.7. Swelling capacity and degradation test of the the coating plate method and the determination method
GADQ hydrogels of bacterial concentration is described in section S4 of
The swelling properties of hydrogels were determined by the Supplementary File . About 10 CFU/mL of E. coli
5
[48]
gravimetric analysis. The degradation test was described and S. aureus suspension (40 μL) were evenly mixed into
Volume 9 Issue 2 (2023) 441 https://doi.org/10.18063/ijb.689