Page 300 - IJB-10-4

International Journal of Bioprinting Analysis of PVA-silk fibroin stents

the surface of a blood vessel is injured, such as during In the present study, fibroblasts proliferated and
stent implantation. In addition, the main function colonized the entire surface of the fabricated BRS within 9
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of fibroblasts is the formation and maintenance of the days (Figures 7 and 8). Moreover, the progression of cells
extracellular matrix. Absorbance units after 2 days on the stent was evident, as they covered the entire surface
indicated satisfactory cell viability on the stent. The within a short period. On day 5, the fibroblasts were still
results for the stents were similar to the PCL electrospun proliferating on the stent surface, but by day 9, they had
scaffolds, a noteworthy result considering that the surface colonized most of the stent (Figure 7). Notably, this study
5
area of the stent was approximately three times smaller was based on seeding 1 × 10 cells per well, whereas other
7
than the surface area of the PCL scaffold. This suggests similar studies on stents usually employ 1 × 10 cells to
that cells had a higher affinity for the SF-coated stent than fully cover the stent surface. In the aforementioned study,
the PCL scaffold. Interestingly, despite the higher surface they followed an acidic post-treatment and silanization
area of the PCL-fabricated scaffolds, they exhibited to improve cell adhesion and achieved comparable cell
comparable rates of cell proliferation throughout the adhesion on the stents within 48 h.
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experiment. Furthermore, cell viability results after 5, For robustness, the proliferation studies were
7, and 9 days indicated cell proliferation to occupy the replicated and evaluated by SEM, which corroborated the
entire stent surface. results previously found. The SEM images also indicated
These findings are relevant as researchers have sought that the entire surface was covered by the cells, leaving
to enhance cell adhesion and proliferation to stents by no gaps on the stent surface at 9 days post-seeding,
means of post-processing with other materials different indicating a robust affinity of the cells for the substrate.
from those employed in the core of the stent to withstand Additionally, it also observed that the fibroblasts were
compression forces. For instance, Wang et al. addressed undergoing division to cover the rest of the surface at 5
this challenge by coating metallic stents with poly-l-lysine days post-seeding. Furthermore, it could be observed that
and fibronectin, resulting in a three-fold improvement the cell morphology exhibited a stretched appearance,
under controlled conditions. Other researchers have with cells collectively enveloping the material until it was
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employed natural polymers, such as gelatin, to improve cell surrounded, indicating a robust affinity of the cells for
adhesion to metallic stents. In other studies, vitronectin the substrate.
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was used to improve endothelization. Uncoated stents Coating the stent with SF is a promising strategy
displayed poor cell proliferation, whereas vitronectin- to promote cell viability and improve the mechanical
coated stents demonstrated denser endothelization. properties of the stent. Specifically, cardiovascular
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Consequently, additional processes are often required to stents aim to maintain arterial structure with the
promote endothelization or cell proliferation in metallic thinnest possible strut, making enhanced mechanical
stents. This holds true for BRS, as Guerra et al. observed properties highly desirable. Thicker struts are known
that fibroblasts seeded on untreated PCL and PLA stents to cause turbulent flows, which are associated with in-
led to proliferation results similar to those observed in stent restenosis. Among the tested groups, the PVA-
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PVA (Figure 5). Hence, researchers are exploring the SF-Coating hydrogel presented the best scores in DMA.
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functionalization of polymers, such as poly-l-lactic acid Additionally, the biocompatibility results reported no
(PLLA) or poly-l-lactide-co-ε-caprolactone (PLCL), for statistical differences, suggesting that only the PVA-SF-
the fabrication of BRS using linear RGDS and YIGSR Coating strategy is suitable for stent manufacturing. In
peptide sequences. In terms of 3D-printed PVA stents, particular, this approach avoids the need for additional
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Boyer et al. evaluated their biocompatibility by seeding processes, such as peptide functionalization, plasma
cells on them. The fabricated stents were for biliary treatment, or acid treatment, which facilitates the
20
application as they were 2-mm thick. They were printed fabrication process. 40,41,43 In vitro mechanical testing
with fused deposition modeling (FDM) filaments and corroborated the aforementioned benefits of SF coating
crosslinked with glutaraldehyde. In addition, they were (Figure 9). The DMA results illustrated that SF could
coated with barium sulfate for X-ray visualization. Similar increase the E´ capacity of PVA at 25°C, both when
cell viability results were obtained after post-treatment mixed into the solution for stent fabrication and when
with collagen. Thus, two post-treatments and one coating used as a coating. In addition, the E´ of PVA-SF-Coating
were necessary. In the present article, the printing method was approximately four times higher than that of PVA
itself allows the addition of radiopaque agents, and a alone. This improvement is consistent even at higher
single coating is sufficient to improve biocompatibility. In temperatures, maintaining the same trend at 37°C, which
addition, the coating improves the mechanical properties is the human body temperature. SF in solution has twice
of the stent. the E´ value compared to PVA. This increase is also

Volume 10 Issue 4 (2024) 292 doi: 10.36922/ijb.3444