Page 544 - IJB-10-3

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

degree of approximately 88–92% facilitates dissolution was dried and stored. A schematic representation of the
(water temperature from room temperature to 40°C). biofunctionalization reaction is displayed in Figure 3.
Water solubility is also affected by the M of PVA, and the
w
crystallinity is further affected by thermal treatment. 2.7. Characterization
An increase in M or crystallinity negatively influences 2.7.1. Fourier-transform infrared spectroscopy
w
water solubility. The PVA filament used for channel The Fourier-transform infrared spectroscopy (FTIR)
development was water-soluble at room temperature (i.e., spectra of PVA grafts were recorded on a Bruker Vertex 70
complete dissolution after 6–9 h at room temperature). FTIR spectrophotometer with attenuated total reflectance
−1
The crosslinking process with GA was performed in (ATR) over 32 scans and 4 cm resolution in the mid-
aqueous media, which may be inconvenient from a InfraRed region.
dissolution perspective. To decrease PVA solubility at 2.7.2. X-ray diffraction
room temperature, thermal treatment was proposed to X-ray diffraction (XRD) spectra were recorded using the
increase the degree of crystallinity. In this context, both the Panalytical X’PERT MPD X-ray Diffractometer in the 2θ
PVA filament and the PVA-printed channels underwent range of 10–80°. A CuKα-radiation X-ray beam with a
thermal treatment at 50°C (above the glass transition wavelength (λ) of 1.5418 Å was used. XRD analysis was
temperature [T ]) for 1 and 3 days. The samples were conducted to investigate the effect of thermal treatment
g
labeled 0D (without any thermal treatment), 1D (1-day on the degree of crystallinity for both PVA channels (not
thermal treatment), and 3D (3-day thermal treatment), crosslinked) and filaments.
respectively, i.e., Filament 0D, Filament 1D, Filament 3D,
Printed 0D, Printed 1D, and Printed 3D. 2.7.3. Differential scanning calorimetry
The NETZECH differential scanning calorimeter (DSC)
2.5. Crosslinking process 204 was used to investigate the thermal and structural
All channels subjected to crosslinking were derived behavior of PVA channels (not crosslinked) and filaments.
from the untreated filaments. The crosslinking process The analysis was performed in a nitrogen atmosphere
was performed using GA aqueous solution. The printed (99.99% purity) with a 5°C/min heating rate and two
channels (0D, 1D, and 3D) were subjected to crosslinking complete heating–cooling cycles. Samples weighing 20 mg
for 3 and 24 h (each sample was performed in triplicate) were placed into aluminum pans, covered, and secured
to study the effect of time. The samples are referred to as onto the sample platform.
0D-3H (no thermal treatment; 3 h crosslinking), 0D-24H
(no thermal treatment; 24 h crosslinking), 1D-3H (1- 2.7.4. Swelling measurements
day thermal treatment; 3 h crosslinking), 1D-24H (1-day The swelling behavior (SD) of PVA grafts (both dried and
thermal treatment; 24 h crosslinking), 3D-3H (3-day crosslinked PVA channels) was assessed in phosphate-
thermal treatment; 3 h crosslinking), and 3D-24H (3-day buffered saline (PBS) at 37°C. The mass change was
thermal treatment; 24 h crosslinking). After crosslinking, recorded at regular time intervals during the swelling
the channels were dried at room temperature for 1 week. process. The swelling degree was determined according to
The dried channels were immersed in a water bath for 1 the following equation:
day and dried again at room temperature for 1 week. After
the crosslinking and drying-washing cycles were complete, W − W 0
t
the samples were considered PVA grafts (small veins). SD = W 0 ×100% (I)
2.6. Biofunctionalization of poly(vinyl alcohol) where W and W represent the weight of the swollen
graft with lysine samples at a predetermined time and the weight of the
t
0
Graft biofunctionalization plays a specific role in initial sample, respectively. The swelling measurement
improving biocompatibility and cytotoxic responses. The was conducted in triplicate for each sample. Swelling
3D-3H graft was subjected to biofunctionalization with equilibrium was achieved when the weight of the swollen
lysine. A lysine aqueous solution was prepared (2% w/v) sample remained constant.
at room temperature for 1 h (pH 8–8.5). Vascular grafts
were added to the lysine solution: four grafts (~0.2 g each) 2.7.5. Morphological investigation by scanning
in 20 mL solution. The biofunctionalization reaction was electron microscopy
performed for 8 h at room temperature. After the reaction, Morphological investigation of the functionalized vascular
the samples were washed with distilled water and placed in graft surface was performed using scanning electron
a glass bottle for purification for 1 week. The final sample microscopy (SEM). The analysis was performed using the

Volume 10 Issue 3 (2024) 536 doi: 10.36922/ijb.2193