Page 247 - IJB-9-2

International Journal of Bioprinting Coronary and peripheral artery disease. State of the art.

Figure 10. (A) Digital stent prototype optimized for PBF 3DP. (B) Scanning electron microscopy images of printed VS after electrochemical polishing;
images at the upper panel belong to VS produced by hatching PBF scanning, whereas images at the lower panel correspond to a stent produced with
concentric scanning PBF. (C) Scanning electron microscopy images of 3DP CoCr VS produced by hatching (top) or concentric strategy laser scanning
(bottom) and their differences. Laser pulse duration is indicated in each case. Reproduced with permission from [37] 2019, Materials & Design.

surfaces. Gamma-irradiation was an effective sterilization higher radial strength but lacked flexibility, as compared
procedure, although it also affected the structure of the to their coil counterparts. Afterward, VS geometries have
polymers and their biological performance. haSMCs greatly evolved and changed, with more complicated and
proliferation and metabolic activity were inhibited due to perfected geometries included, and are adapted to their
surface modifications of the polymers during sterilization, final scope (Table 3). Nowadays, coil stent geometries
while EPCs were unaffected. Flege et al. highlighted this are more commonly used for non-vascular stents, being
result as a positive one, since it “might favor the prevention more frequent to find helical spiral designs for VS. Woven
of neointimal hyperplasia in stented vessels” . This (braided or knitted) designs can be made of more than
[78]
study demonstrated the versatility of 3DP techniques to one strand (made of different materials) and they are
be adapted to print a wide variety of materials, meaning traditionally used for the production of self-expandable
that none of them can be dismissed as useful ally in the VS, although balloon-expandable examples can also be
production of medical devices in future. found. VS with individual rings frequently use zig-zag
wire (struts) that should be attached to one another to
5. Computational studies and 3D printing form the final stent or vascular prosthesis. If individual
rings are connected to each other with a certain consistent
Several studies have demonstrated that stent design features pattern, the stent possesses the so-called “sequential
are of great importance for a successful treatment due to ring connection.” In this occasion, the zig-zag struts are
correlations with thrombosis and in-restenosis risk [33,79,80] . connected through “bridges,” “hinges,” or “nodes,” placed
For better clarity and understanding of this section, a in every strut inflection point (regular connection), in a
schematic representation of the most important stent parts subset of inflection points alternating with unconnected
and their nomenclature are included in Figure 11A.
ones (periodic connection) or they can be placed to
The implanted VS induces disturbances in blood flow join the outer radii (peak-peak bridging elements) or to
and alters shear stress of wall vessels at the strut level. join inner radii with outer radii (peak-valley bridging
These factors highly influence the pathophysiological elements). The stent bridges can have different shapes
mechanisms leading to VS complications . Focusing such as V, L, N, W, S shapes, etc., as well as multiple shapes
[81]
on the structural and geometrical design of VS, the first all combined in the same structure (Figure 11C). These
manufactured stents could be classified into slotted connections play an important role in the optimization
geometries and coil geometries. The former ones possessed of the final performance of the stent, especially in their

Volume 9 Issue 2 (2023) 239 https://doi.org/10.18063/ijb.v9i2.664