Page 128 - IJB-9-1

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

quickly, and the water contact angles after 1 s were 54.55 ± offered stout “houses” for tumor cell proliferation and
1.21°, 43.78 ± 2.34°, and 19.30 ± 3.39°, respectively, further development of tumor sphere.
indicating that the hydrophilicity of the scaffolds was The porous structure of scaffolds could promote
greatly improved. The water contact angles of a series of cell adhesion and proliferation. High porosity and close
porcine skin dECM/ gelatin/chitosan scaffolds prepared by connection between pores can ensure effective mass
Xu et al. ranged from 84.84° to 126.25° at 0 s. Moreover, transfer between high-density cells and improve water
[34]
with the addition of dECM, water droplets penetrated the absorption . To evaluate whether the scaffolds were
[67]
scaffolds at a slower rate, remaining between 52.75° and suitable for cell inoculation, the porosity of the three groups
70.25° after 3–6 s. The scaffolds prepared in our study were of scaffolds was investigated. The results were shown in
more hydrophilic. Figure 4K, which turned out to be 61.02 ± 6.95%, 76.62 ±
In order to support the growth of cells and the 4.43%, and 64.68 ± 1.21%, respectively. It had been reported
formation of tumor spheres, the scaffold should have that with the increase of hydrogel material concentration,
a certain mechanical strength, so that it can stand the the average pore size of the scaffold decreased and
weight of cells filling the entire scaffold. Therefore, the porosity increased after lyophilization, which was due
compression performance of the scaffold was tested, to the influence of solution viscosity, ice crystal size, and
and the results were shown in Figure 4I. It can be seen nucleation rate during lyophilization. It can be seen in the
that when the strain reached 0.5, the stress of the three results that although the total concentration was the same,
scaffolds could reach more than 1000 Pa, among which the porosity of 6G3S1d was higher than that of 7G2S1d,
6G3S1d showed the best compression performance. When possibly because sodium alginate forms a more stable
the scaffold was compressed, the stress-strain curves was network after crosslinking by Ca 2+[21,68] .
nearly a straight line at first, which is called the elastic Hemolysis test results of scaffolds were shown in
deformation stage, and the relationship between stress and Figure 4L. It could be observed that in the positive control
strain follows Hooke’s law. Then, the scaffold enters the group, red blood cells were lysed as a result of osmotic
micro-plastic strain stage and yield stage as it continues pressure inside and outside the cells, while in the solutions
to be compressed. Therefore, a tangent line was taken for of the three groups of scaffolds, red blood cells precipitated
the part at the beginning of the compression curve, which at the bottom of the tubes were not lysed and the solutions
was nearly straight, and its slope was the compression were clear and transparent, which was similar to the
modulus. The results were shown in Figure 4J, turning results displayed in the negative control group. It could be
out to be 22.68 ± 0.28 kPa, 29.64 ± 0.41 kPa, and 42.90 ± preliminary evidence that substances harmful to the cell
0.19 kPa, respectively. The 3D printed scaffold based on were not contained in the scaffolds.
hydroxyethyl cellulose/sodium alginate/gelatin (HCSG)
composite biomaterial prepared by Li et al. was no more 3.5. Biocompatibility
[64]
than 50 kPa at a strain of 0.6, and the GelMA hydrogel In order to further evaluate the biocompatibility of the
prepared by Peela et al. for the construction of breast scaffolds, mouse fibroblasts L929 were inoculated on the
[65]
cancer model had a compression modulus of 748 ± 90 Pa. scaffolds and observed by confocal laser microscope on
The three groups of 3D-printed scaffolds prepared in our 1 d, 4 d, and 7 d, respectively, as shown in Figure 5A–C.
study exhibited better compression performance, and the Calcein-AM contains methyl acetate with high lipophilic
stress could all reach more than 1000 Pa when the strain properties, which can pass through the cell membrane, and
was only 0.5, and the compression modulus of 5G3S1d go through the action of esterase inside living cells. The
was also more than 20 kPa, indicating that the scaffolds remaining Calcein can emit strong green fluorescence at
prepared in our study were not easy to deform and could the excitation wavelength of 490 nm. PI is commonly used
meet the requirements for inoculating cells. It had been as a nuclear stain. It cannot pass through the membrane of
reported that the behavior of tumor cells was sensitive, and living cells, but it can pass through the membrane of dead
dependent on the mechanical forces in the extracellular cells, and reach the nucleus, embedding into the DNA
matrix, so scaffolds with high mechanical strength were double helix structure and emitting red fluorescence at the
conducive to the adhesion and migration of tumor cells . excitation wavelength of 535 nm. Therefore, Calcein-AM
[66]
The high mechanical strength of these scaffolds was and PI are usually used as fluorescent staining agents to
attributed to the double crosslinking of Ca and EDC/ label living cells and dead cells, respectively. From Figure
2+
NHS crosslinkers, which also restricted the degradation 5A–C, it can be seen that with the increase of incubation
ratio of these scaffolds by serum enzymes (lysozyme and time, quantity of living cells on the scaffolds also gradually
collagenase) to some extent (Figure S1). The appropriate increased. On 4 d, cell clusters had appeared on the scaffold
mechanical strength and degradation rate of these scaffolds (white arrows), and the diameter of cell clusters increased

Volume 9 Issue 1 (2023) 120 https://doi.org/10.18063/ijb.v9i1.630