Page 542 - IJB-10-3

International Journal of Bioprinting Engineered 3D-printed PVA vascular grafts

properties (crosslinking density, biofunctionalization, conditions (37°C; 5% CO ; 90% humidity). L929 fibroblast
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and elasticity) of PVA grafts require adjustments to be cells (ATCC, USA) were cultured in Dulbecco’s Modified
comparable to those of natural blood vessels as they are Eagle Medium (DMEM), supplemented with 10% fetal
directly correlated to the crystalline and amorphous phases bovine serum and 1% Penicillin-Streptomycin (Gibco,
of PVA. The balance between crystalline and amorphous USA), in standard conditions (37°C; 5% CO ; 90%
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regions in polymers, including PVA can be optimized humidity). U937 monocyte-like cells (ATCC, USA) were
through thermal treatments. 51,52 Fabrication technique cultured in Roswell Park Memorial Institute Medium
and parameters significantly influence compliance and (RPMI) 1640, supplemented with 10% fetal bovine serum
mechanical integrity. A gold standard for these vascular and 1% Penicillin-Streptomycin (Gibco, USA), in standard
grafts is rapid re-endothelialization of the luminal surface, conditions (37°C; 5% CO ; 90% humidity). Vascular graft
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as a healthy endothelium prevents thrombosis, stenosis, samples were sterilized through gamma radiation exposure.
and intimal hyperplasia. 53,54 PVA vascular grafts have
reported excellent bio-inertness, low thrombogenicity, 2.3. Design and 3D printing
high water content, and tunable properties, but challenges, The design of the channels and platform was created using
such as immune response, rapid re-endothelialization, and Fusion 360 software. The channels had a diameter of 0.8
complex viscoelastic behavior, remain to be addressed. mm, a wall thickness of 0.4 mm, and a length of 50 mm
(Figure 1A). The 3D printing model of the channels was
This study presents an innovative approach for the configured using FlashPrint Software, version 5.5.1, Zhejiang
fabrication of PVA vascular grafts using fused deposition Flashforge 3D technology Co., LTD before printing. In brief,
modeling. This approach is developed to enhance the the channels were secured on a support structure made
production of small vascular grafts, vital in treating from PLA (Figure 1B). The 3D printing parameters for the
cardiovascular disorders. This study aimed to address PVA channels were as follows: the hot end temperature
two key challenges: optimizing mechanical properties was set to 220°C for PVA and 210°C for PLA, while the
and enhancing biocompatibility. Herein, we present platform temperature was maintained at 60°C. The platform
the design of 3D-printed PVA channels subjected to dimensions were 14 mm in height, 22 mm in width, and 50
thermal treatment, crosslinking, biofunctionalization, mm in length (Figure 1C). Before printing, the platform 3D
and comprehensive assessments. Taken together, we have printing model was configured in FlashPrint software with
established a suitable protocol for producing small vascular the addition of supports (Figure 1D).
grafts and demonstrated that the optimization process For the PETG platform, the 3D printing parameters
could significantly affect graft properties.
included a hot end temperature of 240°C (due to the
2. Materials and methods closed enclosure), with the platform temperature set to
70°C. Additionally, the 3D-printed platform was coated
2.1. Materials with acrylic resin on its surface to prevent fluid leakage.
PVA (average M : 85,000–124,000 g/mol, 87–89% Acrylic resin is composed of a mixture of two monomers,
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hydrolyzed; Sigma-Aldrich, United States of America diurethane dimethacrylate and triethylene glycol
[USA]), high M poly(lactic acid) (PLA) (PLA Crystal dimethacrylate, in a 1:1 weight ratio. The curing initiation
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Clear, M : 182,000 g/mol; Fillamentum, Czech Republic), system consists of a blend of DL-CQ and EDMAB in a
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and polyethylene terephthalate glycol (PETG) (PolyLite 1:4 weight ratio. This curing mixture accounts for 1% (by
PETG, M : 300,000 g/mol; Polymaker, China) filaments weight) of the total amount of acrylic monomers. The
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with a circular profile of 1.7 ± 0.1 mm in diameter curing process was carried out in an ultraviolet (UV)
and processing temperatures of 195–225, 200–210, curing chamber (Figure 2).
and 210–240, respectively, were provided by 3D4ALL
(Romania). Glutaraldehyde (GA) solution (25%) and 2.4. Thermal treatment of poly
acrylic resin (diurethane dimethacrylate, triethylene glycol (vinyl alcohol) channels
dimethacrylate, dl-camphorquinone [CQ], and ethyl PVA is a synthetic water-soluble, whereby its solubility
4-dimethylaminobenzoate [EDMAB]) were purchased is closely associated with its crystallinity and degree
from Sigma-Aldrich (USA). of hydrolysis. PVA is obtained from the hydrolysis of
poly(vinyl acetate) (PVAc). In basic conditions and with
2.2. Cell culture the use of a methanol/ethanol mixture, the acetate groups
We cultured bEnd.3 brain endothelial cells (ATCC, USA) in in PVAc are hydrolyzed into hydroxyl groups. A higher
Advanced Dulbecco’s Modified Eagle Medium (ADMEM), degree of hydrolysis (typically 98–99%) results in increased
supplemented with 10% fetal bovine serum, 1% l-glutamine, crystallinity, which makes dissolution more challenging
and 1% Penicillin-Streptomycin (Gibco, USA), in standard (i.e., dissolution in >80°C water). Conversely, a hydrolysis

Volume 10 Issue 3 (2024) 534 doi: 10.36922/ijb.2193