Page 332 - IJB-10-6

International Journal of Bioprinting 3D-printed PPDO/GO stents for CHD treatment.

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strength (19.21 ± 0.41 MPa), and 16.96% in elongation at eV is deconvoluted, which is attributed to sp carbon. The
break (1.120 ± 0.207). At higher GO content (i.e., reaching O1s peaks are deconvoluted into four components with
5%), the elongation at break drastically decreases by binding energies of 531.5 ± 0.2 eV, 532.2 ± 0.2 eV, 533.1 ±
88.01% compared to that of pristine PPDO. The abundant 0.2 eV, and 534.1 ± 0.2 eV, corresponding to O–C=O, C=O,
functional groups of GO promote uniform dispersion in C–OH, and C–O–C, respectively. By calculating the area
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the PPDO matrix, fostering increased intermolecular percentage of the deconvoluted O1s spectra, it is found that
interactions with the PPDO matrix. Hydrogen bonding the C–OH percentage of PPDO/GO materials exhibits an
enhances the mechanical properties of materials, including increasing trend as the GO content rises (Figure 4d). This
Young’s modulus, tensile strength, and elongation at can be attributed to the abundant hydroxyl groups present
break. 71–74 It facilitates polymer chain crosslinking and in GO, and the finding is consistent with the FT-IR results.
impedes chain movement, thus improving the stiffness of Figure 4e features the water contact angle of PPDO/
PPDO. The elevation in the degree of crystallinity also GO materials. As the GO content increases, the water
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contributes to the improvement of Young’s modulus. GO has contact angle of PPDO/GO materials gradually decreases
an intrinsically high modulus and acts as a reinforcement from 76.2° ± 1.0° of PPDO to 69.0° ± 0.8° of PPDO/5%GO,
in the PPDO matrix. As displayed in Figure 3g, indicating enhanced wettability. The presence of abundant
at 5% GO content, Young’s modulus reaches its peak at hydrophilic groups in GO, such as carboxyl and hydroxyl
179.46 ± 2.76 MPa. Many studies have revealed that as (as observed in the FT-IR and XPS results), improves the
GO content increases, Young’s modulus of the composite hydrophilicity of PPDO. The enhanced hydrophilicity may
material increases as well. 76–78 Wan and Chen reported that facilitate HUVEC adhesion and proliferation. 86,87
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at higher GO content, Young’s modulus of the composite
material gradually increases despite poor dispersion. The melt viscosity of the material is crucial for FDM.
GO reinforces the PPDO matrix due to its intrinsic high The material needs to have sufficiently low viscosity to
strength and enables more effective load transfer from ensure continuous extrusion through the nozzle, while also
the matrix to the nanofiller through hydrogen bonding, exhibiting shear thinning behavior, where melt viscosity
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enhancing the tensile strength of PPDO/GO materials. At a sharply increases when the shear rate decreases. This
higher level of GO content, the aggregation of GO impairs helps the material maintain its shape after extrusion under
load transfer efficiency and results in poor reinforcement. gravity and the stress from the deposition of subsequent
Under external load, micro-cracking is formed at the layers 88,89 . As displayed in Figure S4, both PPDO and
matrix–GO interface during crack propagation and absorbs PPDO/GO materials exhibit shear thinning behavior, and
plenty of fracture energy. Besides, GO nanosheets can the melt viscosity decreases as the temperature increases.
prevent crack propagation by crack deflection and crack The incorporation of GO enhances the melt viscosity of the
pinning, 81–83 thereby enhancing the toughness of PPDO/ PPDO matrix, which is also observed in polyamide 6/GO
GO materials. However, the high degree of crystallinity of composite. This may be due to the improved interaction
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PPDO leads to a decrease of elongation at break at higher between PPDO and GO under hydrogen bonding.
GO contents. According to the results of the mechanical The design of sliding-lock stents is inspired by cable
characterization of PPDO/GO composites, the mechanical ties. Stents with a series of diameters can be fabricated
properties of PPDO are enhanced when GO contents by adjusting the lateral dimension. Figure 5a features
are at 0.2% and 0.5%. Therefore, PPDO/0.2%GO and the 3D-printed PPDO/GO sliding-lock stents. FDM
PPDO/0.5%GO are selected for stent fabrication and can accomplish personalized customization of vascular
subsequent biocompatibility evaluation. stents with intricate structures and is suitable for printing
The XPS analysis characterizes the surface element thermoplastic polymers (PPDO, PLLA, PLGA, etc.),
composition and the chemical states of carbon and oxygen exhibiting the advantages of convenience, speed, and cost-
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in PPDO/GO materials. The wide scan spectra (Figure 4a) effectiveness. The thickness of PPDO, PPDO/0.2%GO,
indicate that PPDO/GO materials are composed of and PPDO/0.5%GO sliding-lock stents is measured
carbon and oxygen, and no fluorine is detected, implying as 257.20 ± 5.73, 263.20 ± 6.35, and 256.69 ± 2.86 mm,
the complete removal of the HFIP solvent. The high- respectively. Figure 5b and c demonstrate the front and
resolution spectra of C1s and O1s core levels of PPDO/GO top views of PPDO/GO sliding-lock stents (diameter:
materials are displayed in Figure 4b and c. The C1s peaks 9 mm), respectively. Compression performance is one
are deconvoluted into three components with binding of the primary properties of vascular stents. Results of
energies of 284.8 eV, 286.6 ± 0.2 eV, and 288.9 ± 0.2 eV, parallel plate compression tests (Figure 5d) reveal that
corresponding to C–C, C–O, and C=O, respectively. 84,85 For incorporating GO significantly enhances PPDO sliding-
GO, another component with a binding energy of 284.4 lock stents’ compression performance. The compression

Volume 10 Issue 6 (2024) 324 doi: 10.36922/ijb.4530