Page 301 - IJB-10-4

International Journal of Bioprinting Analysis of PVA-silk fibroin stents

maintained in the temperature range of 25–50°C. The fabrication methods, such as SC-DW, but using different
E´ values found for PVA align with those reported in the materials such as PLLA and PLCL, the results varied. Stents
literature. In addition, literature values for SF indicate with similar geometry to those presented in this study
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an E´ of approximately 3 GPa at 37°C. Since there was using the SC-DW method reported a maximum force of
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more PVA than SF in the fabricated samples, the observed 2.7 N, but the stents were 33% longer. In addition, the
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values are reasonable. They are superior to PVA and fabrication of self-expandable FDM PLA stents reported
inferior to SF, which is consistent with the dominance a markedly greater ability to withstand compression.
of PVA as the primary material. The values of E´ could However, it is important to note that the diameter, length,
be increased even further since weighted calculations of and strut size of these stents were larger. 50
the presence of each material could be higher. However, Finally, both PVA and PVA-SF-Coating stents were able
the complexities of the molecular arrangements of the to compress to 50% of their original diameter and return
polymers influence the mechanical properties. Ideally, to the starting position with an elastic recovery >90%
the molecular structures of SF and PVA should mesh (Figure 9b). As the results indicate, this is a property in
together, promoting attractive forces for synergistic which PVA outperforms SF, as PVA alone exhibited superior
mechanical enhancement. Weak interactions could elastic recovery due to its improved elastic properties.
limit this potential, making enzymatic crosslinking In contrast, SF alone is a significantly brittle material. 24,51
an attractive alternative. This method allows in situ In fact, SF alone could never undergo the hysteresis cycle
hydrogels to be generated under mild conditions and with illustrated in Figure 9b, as it lacks sufficient capacity to
minimal cytotoxicity, facilitating enhanced crosslinking deform and return to its original state. Remarkably, the
between PVA and SF. Although the addition of SF to multi-material PVA-SF stent provides significant added
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the PVA solution improves E´, strategies to optimize value because it provides a compromise between the best
material interactions are available to further improve properties of each material.
performance. Previous evaluations using differential
scanning calorimetry (DSC) revealed that ultrasound 5. Conclusion
could further refine the PVA-SF interactions. Hence,
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the study not only presents a robust PVA-SF-Coating PVA is a promising material for the fabrication of BRS
approach but also opens opportunities for continuous using additive manufacturing technologies. Despite
improvement in material synergy. their potential, PVA hydrogels face challenges, such as
low cell adhesion and decreased mechanical properties,
In the analysis of the compression data, it was determined
that the coated stent had an average SF layer thickness of compared to their metallic alternatives. To overcome
these limitations, SF was introduced by two approaches:
63 µm. This is within the range observed for SF dip-coating (i) dissolving SF in solution and (ii) coating the PVA
when two cycles are employed, taking into account the hydrogel with a layer of SF.
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higher hydrophilicity of PVA compared to stainless steel.
Approximately 3% of the stent thickness is attributed to SF Preliminary tests on the activation solution revealed
and the rest to PVA. Remarkably, this minor variation in stent that FBS significantly increased cell viability in the
material composition resulted in a substantial mean increase hydrogels. This highlights the increased cellular response
of 42.9% in stent compressive strength capacity. Importantly, to FBS-containing proteins, such as laminin or fibronectin,
this increase has already been weight-normalized, ensuring which are found in higher concentrations in FBS than in the
that the impact of the additional material is considered in activation medium. Furthermore, cell proliferation assays
the increase in compressive strength. indicated that the addition of SF substantially improved
cell viability compared to PVA alone, highlighting the cell
Comparison with other stent studies presents
difficulties due to variations in stent geometry and size. viability capabilities of SF-modified hydrogels.
While some PVA stents in the literature exhibit a maximum Additionally, PVA-SF-Coating stents were fabricated
compressive force of approximately 5 N, the stents in the employing this method. The results found in hydrogels were
present study displayed a maximum compressive force corroborated, especially in terms of cell proliferation and
of 1 N. Nevertheless, the denser mesh geometry in the stent colonization. Fibroblasts exhibited strong adhesion
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literature was a key factor in the observed variations, and proliferation in PVA-SF-Coating stents, indicating a
indicating that more material was used for the fabrication higher affinity for SF than for electrospun PCL scaffolds. This
of the cited stents. Stents with a geometry similar to that cellular response in PVA-SF-Coating stents positions them
presented in this study demonstrated lower maximum as promising candidates for cardiovascular applications,
compression forces, despite being immersed in chitosan suggesting enhanced biocompatibility, which at the
and cross-linked with genipin. In studies with similar stent same time could potentially improve endothelialization.

Volume 10 Issue 4 (2024) 293 doi: 10.36922/ijb.3444