Page 45 - IJB-9-5

International Journal of Bioprinting Precise fabrication of engineered vascular networks

Then, the flexibility in fabricating 3D engineered printed sacrificial template and polymerize it under UV
vasculature was verified by the 3D printing sacrificial light. The edge of the hydrogel scaffold was cut to expose
template with multiple layers. HUVECs were cultured the sacrificial template and placed at 4°C for 20 min to
in the engineered vasculature to form the endothelial remove the sacrificial template. Subsequently, ultrapure
monolayer, and the biocompatibility of the engineered water was gently injected to fully clear the engineered
vasculature fabricated by our proposed method was tested. vasculature. Finally, the hydrogel scaffold with engineered
In addition, osteosarcoma cells (OCs) were loaded into vasculature was placed in a 35-mm Petri dish, which was
a hierarchical vasculature within the thermoresponsive left to float in a 37°C water bath to precisely fabricate
hydrogel to study the interaction between human umbilical the designed vasculature. The diameters of the printed
vein endothelial cells (HUVECs) and OCs. P/G hydrogel sacrificial template and the channel at different times were
scaffolds with vasculature were implanted into animals to measured under an optical microscope.
study vascular infiltration and reconstruction within the
vasculature. 2.3. Effect of PNIPAM/GelMA (P/G) concentration on
swelling compensation
To study the effect of P/G concentration on the precise
2. Materials and methods fabrication of the engineered vasculature, P/G , P/G ,
1
3
2.1. Materials and reagents and P/G hydrogels were prepared. The composition
5
N-isopropylacrylamide (NIPAM) monomer and N, of the P/G , P/G , and P/G hydrogels is summarized in
3
5
1
N’-methylenebisacrylamide (MBA) crosslinker were Table S1 (Supplementary File). A 20-G needle was used
purchased from Aladdin, China. The photoinitiator, in this section. The engineered vasculature was fabricated
lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), as the above protocol. Then, the hydrogel scaffolds with
sodium alginate (low viscosity), gelatin, and PF-127 engineered vasculature shrunk at 37°C, and the change in
were purchased from Sigma-Aldrich, USA. GelMA was areas and diameters of the vasculature was recorded. The
purchased from Engineering For Life (EFL) at the Suzhou diameter of the vasculature was measured under an optical
Intelligent Manufacturing Research Institute, China. In microscope. The area of the P/G hydrogel scaffold was
this study, 30 g PF-127 was dissolved in 100 mL ultrapure quantified using ImageJ software. The shrinkage ratio SR
water to prepare the sacrificial PF-127 solution, unless was computed using the following formula:
otherwise indicated. (I)
2.2. Swelling compensation for 3D-printed
vasculature where A was the area of the as-prepared P/G hydrogel
1
A customized 3D printer based on a fused deposition scaffold, and A was the hydrogel scaffold area after
2
modeling (FDM) printer (Tenlog, China) and syringe shrinking.
pump (Shengchen, China) was used to print the sacrificial 2.4. Effect of vasculature density on swelling
materials. To print with precision, the sacrificial template compensation
with a designed diameter, 19-G (I. D. 720 μm, O. D. To investigate the effect of vasculature density on volume
1080 μm), 20-G (I. D. 610 μm, O. D. 910 μm), and 21-G shrinkage, three patterns of sacrificial templates were
(I. D. 520 μm, O. D. 820 μm) needles were used to print designed. Patterns 1, 2, and 3 have three, six, and nine
the zigzag structure. Different feed rates of the syringe fibers, respectively. P/G , P/G , and P/G were used as the
2
4
3
pump were set to check the printability and diameters hydrogel concentrations, and a 20-G needle was utilized.
of the sacrificial templates. To preliminarily validate the After the removal of sacrificial templates, the scaffolds
hypothesis that the volume shrinkage of the P/G hydrogel with different patterns of vasculature were placed at 37°C
can compensate for the swelling induced by the removal of to record the diameters and areas at 0, 0.5, 1, 2, 3, 4, and
the sacrificial template, the sacrificial PF-127 was printed 5 h. The shrinking ratio was calculated using Equation I.
on the P/G film. In this experiment, 10 wt% NIPAM,
0.15 wt% MBA, 3 wt% GelMA, and 0.075 wt% LAP were 2.5. Fabrication of 3D vasculature
dispersed in ultrapure water homogeneously to prepare the To fabricate 3D vasculature based on the proposed method
P/G solution. Then, 1.5 mL P/G solution was transferred in order to enhance the mass transfer, sacrificial templates
3
3
to a 35-mm Petri dish and polymerized under UV light at with two, four, and six layers were designed. The images of
a distance of 10 cm for 20 s. After that, the polymerized engineered vasculature after dissolving and shrinking were
P/G hydrogel was placed on the receiving platform of the captured. Red acrylic paint was injected into the engineered
3
customized printer to print the zigzag sacrificial template. vasculature to show the 3D structure. P/G was used as the
3
After printing, 1.5 mL P/G solution was used to cover the hydrogel concentration, and a 20-G needle was utilized.
3
Volume 9 Issue 5 (2023) 37 https://doi.org/10.18063/ijb.749