Page 291 - IJB-10-4

International Journal of Bioprinting Analysis of PVA-silk fibroin stents

associated with long-term complications, this pioneering with the cardiovascular system, demonstrating a reduction
research direction has garnered significant interest of thrombosis-associated outcomes. Additionally, SF
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from the scientific community. In this context, additive has reported promising results in inhibiting smooth
1
manufacturing is emerging as a transformative tool capable muscle cell proliferation, which is a desired feature in
of giving BRSs the potential for customization, which can stent design. This, coupled with the fact that PVA and
15
improve their performance. The first 3D-printed BRS on a SF can be three-dimensional (3D) printed by different
tubular surface was presented by Guerra et al. Since then, additive manufacturing techniques, such as SC-DW
2
many other techniques have emerged for the fabrication extrusion or light-assisted printing, makes them suitable
of this medical device, such as stereolithography, selective for 3D printing multi-material stents and warrants further
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laser sintering, etc. Another prominent technique investigation. In particular, both PVA and SF are water
3–5
employed for the fabrication of cardiovascular stents soluble, facilitating their miscibility to form a water-based
is the solvent-cast direct-writing extrusion (SC-DW) ink that satisfies the rheological requirements for direct ink
technology. A distinguishing feature of this technique is writing (DIW) printing.
6
that it allows the incorporation of drugs or radiopaque Previously, PVA stents were investigated, focusing
agents into the stent, improving its visibility under X-rays primarily on optimizing printability, characterizing stent
6,7
and overall performance. Furthermore, it offers flexibility kinetics, and evaluating the mechanical properties of the
in the use of various materials as it is relatively easy to find material. However, despite significant advances in these
19
an organic solvent to dissolve the desired material into a areas, the challenge of achieving robust cell adhesion and
paste. The main challenge lies in achieving the required proliferation in PVA stents still prevails. This limitation
rheological properties to ensure accurate print resolution. has resulted in the present study, which evaluates the
8
In earlier studies, an investigation was undertaken to potential of incorporating SF to address these challenges
explore the feasibility of fabricating BRS using polyvinyl in the design of cardiovascular stents. The hypothesis
alcohol (PVA) employing a custom SC-DW tubular 3D postulates that the integration of SF into PVA offers a
printer. Prior to that, PVA had been used for the fabrication dual advantage: significantly increased cell viability and
of stents due to its mechanical properties, which closely additional mechanical properties for the stent structure,
resemble those of aortic vessels. Consequently, PVA has as SF has proven to have a tensile strength significantly
9
demonstrated certain notable characteristics, making it higher than PVA (∼10 fold). 20,21 To test this hypothesis, a
a particularly promising candidate for stent fabrication. dual strategy for stent fabrication was followed: first, to
However, PVA exhibits a low level of cell attachment fabricate stents by making an ink by mixing 28% (w/v) PVA
and proliferation due to its lack of cell-adhesive ligands and 5–7% (w/w) SF in a 1:1 weight ratio, and second, to
and its hydrophilic nature. These properties have been create PVA stents with the aqueous solution of 28% (w/v)
10
demonstrated to be critical in the performance of a PVA, followed by the application of a coating layer of SF.
cardiovascular stent, as they promote endothelialization. Both methods were subjected to evaluation, particularly
Rapid stent endothelialization has been reported to reduce in terms of their compression and cell viability properties,
thrombosis and the risk of restenosis. 11,12 Consequently, with the overall goal of improving the performance of
strategies targeting the enhancement of PVA cell affinity cardiovascular stents.
have gained attention in the literature. These strategies To evaluate the impact of these strategies on cell
often include blending PVA with materials biologically behavior, hydrogels were carefully manufactured from each
derived from an extracellular matrix or other natural approach and subjected to sterilization. These hydrogels
origins, chemical modification, or by modifying their were then used in cellular assays to observe fibroblast
13
surface topography. Silk fibroin (SF) has proven to be a interactions with the materials. Typically, constructs for cell
14
good precursor for improving the non-adhesion properties culture are activated with culture medium to prepare them
of PVA hydrogels. SF is a natural polymer derived for cellular interaction. However, in this study, we adopted
15
from the silkworm Bombyx mori. It has demonstrated a novel strategy by immersing the hydrogels in fetal bovine
biocompatible and biodegradable properties and has been serum (FBS) at the same time intervals. This approach was
widely used in the field of biomedical engineering due to its assessed to determine whether FBS could promote more
mechanical properties. The tensile strength of regenerated proteins to bind with the stent surface than the common
SF for different SF fibers is comparable to steel. Moreover, medium activation method, thereby potentially improving
16
SF exhibits controllable mechanical properties, which cell viability. For comparative analysis, PVA was included
can be adjusted by temperature or sterilization processes, as a control in these experiments. This article discusses in
making it a perfect candidate for medical applications. depth the fundamentals of our novel approach, provides
17
Furthermore, SF has been successfully tested in contact insight into the methodologies employed in the fabrication

Volume 10 Issue 4 (2024) 283 doi: 10.36922/ijb.3444