Page 121 - IJB-9-1

International Journal of Bioprinting Fabrication of 3D breast tumor model for drug screening

distribution graph using Origin Pro 9.5 software to analyze it as m . Then, the scaffold was slowly taken out, and the
2
the pore structure of the scaffolds. pycnometer with the remaining ethanol was weighed as
m . The porosity was calculated using Equation III:
2.6.2. Infrared spectroscopic analysis 3
The chemical structure and the status of chemical bonds φ = m 2 − m 3 − m 0 ×100% (III)
in the scaffolds were investigated by Fourier transform m 1 − m 3
infrared spectroscopy (FTIR). Briefly, the scaffolds were
milled into powder with KBr particles and presented to the The results were averaged in each group by performing
Fourier transform infrared spectrometer (EQUINOX55, three parallel experiments.
Bruker, Germany) to generate infrared (IR) spectra. The 2.6.6. Hemolytic properties
FTIR spectrometer was performed over the wavenumber The scaffold was placed in normal saline. The negative
range of 4000–500 cm with a resolution of 4 cm . control group was given normal saline without the scaffold,
−1
−1
2.6.3. Swelling ratio while the positive control group was given distilled water.
The swelling behavior was characterized by gravimetric 2 mL fresh rabbit blood was added to each group and
analysis . The dried scaffold (m ) was placed in a 24-well incubated at 37°C for 1 h before taken out. The solutions
[38]
1
plate, and completely immersed in distilled water. Then, were centrifuged with a centrifugation rate of 1000 rpm for
the plate was placed in an incubator set at 37°C and taken 5 min to observe and compare whether blood cells were
out every 2 h to be weighed as (m ). Excessive water was lysed.
2
gently absorbed with filter paper before test. The swelling 2.6.7. Water contact angle
ratio was calculated using Equation I: Water contact angles were measured with the method as
m − m described in section 2.3. The surface of scaffold was gently
ϕ = 2 1 ×100% (I) smoothed with a blade, and the water contact angle of the
m 1
The results were averaged in each group by performing scaffold was tested with a contact angle meter with a high-
speed camera. The videos were recorded from the moment
three parallel experiments. the droplets touched the materials, until the droplets
2.6.4. Mechanical properties completely penetrated the scaffolds or became stable on
The surface of the scaffold was ground flat with a blade and the scaffolds. The photos of droplet at 0 s, 0.5 s, and 1 s were
make sure that its thickness was no less than 3 mm. The captured, and the water contact angles were measured by
compression performance of the scaffold was tested using IPP software. The results were averaged in each group by
a universal testing machine (SANS, Shenzhen). Briefly, the performing three parallel experiments.
length, width, and height of the sample were measured with 2.7. Evaluation of biocompatibility and skin model
a vernier caliper and marked as a , b , and l , respectively. construction
1
1
1
The compression was performed with 0.5 mm/min of The scaffolds were cut into the size of 5 mm × 5 mm ×
crosshead speed until the specimen height had decreased 1 mm and immersed in 75% ethanol under ultraviolet light
by 50%. Then, the length, width, and height of the sample overnight for sterilization purposes. The scaffolds were
were measured again as a , b , and l , respectively. The then slaked twice with phosphate-buffered saline (PBS) to
2
2
2
compression modulus was calculated using Equation II: remove residual ethanol as well as UV irradiated for 1 h
Fab/ each time. A cell suspension of fibroblast L929 with the
E = (II) concentration of 2×10 cells/mL was prepared and 10 μL
6
l − ) /
( 1 l 2 l 1 of the cell suspension was inoculated on one side of the
The results were averaged in each group by performing scaffold. After 0.5 h, 300 μL medium was added and the
three parallel experiments. plate was put into a 37°C incubator with 5% CO . After 3 h,
2
2.6.5 Porosity the same amount of L929 were inoculated on the other side
The porosity of the scaffolds was measured by pycnometer of the scaffold and supplemented with 200 μL of medium.
method, and ethanol was used as a substitution liquid 2D control group was directly inoculated with 20 μL of the
because it is not a solvent for the scaffolds . The dry scaffold cell suspension supplemented with 1 mL medium on the
[39]
was weighed as m , and the weight of pycnometer filled well plate.
0
with ethanol was noted as m . The scaffold was immersed The scaffolds inoculated with the cells for 1 d, 4 d,
1
in the pycnometer and placed in a vacuum oven until the and 7 d, respectively, were taken out for fluorescence
air bubbles were completely removed. The pycnometer staining. Briefly, 300 μL staining solution, which was
was taken out and filled with ethanol again and weighed prepared by mixing 1 mL PBS with 2 μL Calcein-AM and

Volume 9 Issue 1 (2023) 113 https://doi.org/10.18063/ijb.v9i1.630