Page 341 - IJB-9-2

International Journal of Bioprinting Characterization of BITC antibacterial hydrogel

used was 4 – 40°C; the rate of temperature change during 2.7. SEM analysis
heating and cooling was 0.03333°C/s; the frequency was The hydrogel morphology was observed under a scanning
1 Hz. The G’ and G’’ were recorded as a function of time. electron microscope (JSM-6510, Japanese electronics).
Each sample was measured in triplicate. The samples were freeze-dried before the test and the test
[25]
2.4. Texture profile analysis (TPA) voltage was 20 kV .
TPA of the gel samples was performed using a SMS-TA. 2.8. Antibacterial activity of the BITC hydrogel
XT PlusC texture analyzer (Stable Micro Systems Co., E. coli MG1655 and S. aureus ATCC25923 strains were
Ltd., UK). Since X-Gel is a liquid and cannot be detected, cultured overnight in lysogeny broth (LB) and Trypticase
we determined the other four types of TPA. The hydrogels Soy Broth (TSB) at 37°C with swirling at 200 rpm . The
[26]
prepared were cut into 1.5 × 1.5 × 0.8 cm blocks for overnight cultures were serially diluted to approximately
3
the measurement of TPA. The TPA test parameters 10 CFU/mL using the corresponding culture media.
7
used were: Cylindrical probe (SMS p/75); the velocity The diluted cultures (200 µL) were evenly spread over
before/during/after measurement was 1.00 mm/s; the strain the agar plate of the culture medium, and then, BITC
rate was 30%; the strain time was 5 s; and the trigger force additions of 0% (control), 0.4%, 0.6%, and 0.8% hydrogels
was 5.0 N. The measurements of each sample were obtained (BITC-XLKC-Gel) were placed on the surface of the solid
in triplicate. media. After 24 h in 37°C incubator, the diameter of
The tensile property was tested using the method inhibition zone was measured to compare the inhibition
described by Ma et al. using a A/MTG physical property effect. The growth inhibition zone of the hydrogel showed
[23]
analyzer (Stable Micro Systems Co., Ltd., UK). The hydrogel that the hydrogel exerted antibacterial activity after 24 h of
[27]
film was cut into 10 × 50 × 3 mm strip and sandwiched incubation at 37°C .
between the splints. The tensile test was performed at a To investigate the scavenging activity of BITC hydrogel
speed of 3 mm/s until the film fracture breaks stopped. on biofilm of S. aureus and E. coli, TSB or LB (100 µL)

2.5. Water distribution was taken into the well of 96-well polystyrene microplate
and the culture medium containing S. aureus or E. coli
Water distribution was measured using the method (10 µL) was separately added. Then, the BITC-XLKC-Gel
described by Yoon et al. using a Niumag Benchtop NMR added with 0, 0.2, 0.6, and 0.8% BITC was added. The
[24]
Analyzer PQ 001 (Suzhou Niumag Analytical Instrument group without bacterial solution and hydrogel was used
Co., Ltd., Jiangsu, China). The hydrogel samples (3 g) were as the blank and incubated at 37°C for 36 h. After biofilm
packed tightly in 2 mL vials (2 mL, 12×36 mm, borosilicate formation, 200 µL sterile phosphate-buffered saline (PBS)
glass – HPLC automatic sampler) and were then placed in was added to each well after the medium was aspirated
a magnetic chamber. The transverse relaxation time (T ) and the gel blocks were removed, and the plate wells were
2
was measured using Carr-Purcell-Meiboom-Gill (CPMG) washed 3 times. Then, 100 µL 1% crystal violet solution
pulse sequence. The test parameters used are as follows: was added to each hole, and biofilm was dyed at room
Sampling frequency = 200 KHz; main frequency = 21 MHz; temperature for 15 min. After aspirating the crystal violet
radio frequency delay = 0.02000 ms; frequency staining solution in the culture medium, the excess dye
offset = 877243.25 Hz; analog gain = 20 dB; 90° pulse was rinsed off with running water , and the plates were
[28]
width = 7 µs; digital gain = 3; sampling points = 3,000,090; inverted on the filter paper to remove residual water and
pre-release gear = 1; waiting time = 5000.000; cumulative then dried in an oven at 37°C or at room temperature.
number of times = 8; 180° pulse width = 13.52 µs; echo After complete drying, 100 µL of 33% glacial acetic acid
time = 1.00000 MS; and number of echoes = 15,000. Each was added to each hole and placed in a 37°C incubator for
measurement was obtained in triplicate. 30 min to dissolve crystal violet. The optical density (OD)
of the solution in the culture well was measured at 595 nm.
2.6. 3D printing of different hydrogels The test was repeated for 3 times for each strain to obtain
The 3D printing of different hydrogels was performed by average value. The culture medium without inoculated
[29]
SHINNOVE-D13D double nozzle printer (Hangzhou bacteria was used as the negative control .
Shiyin Technology Co., Ltd.). The printing parameters are
as follows: Printing temperature was 80°C; nozzle diameter 2.9. Experimental study on the effect of the
was 0.8 mm; material filling ratio was 100%; printing speed hydrogel on the infection of porcine skin after burn
was 25 mm/s; and layer height was 3 mm. 3D-printing The effect of hydrogel on the skin infection of post-burn pigs
characteristics of hydrogels with different compositions was studied according to Lin et al. . The pigskin was cut
[30]
were studied. into 2.5 × 3 cm pieces and soaked in 75% alcohol to remove
2
Volume 9 Issue 2 (2023) 333 https://doi.org/10.18063/ijb.v9i2.671