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

that can be obtained by just changing the feedstock (e.g., In this regard, 3DP enables the production of patient-
some materials are more prone to “shrinking” than others specific medical devices, not only in terms of dimensions
after the printing process). In fact, the major part of the and shape, but also in mechanical properties. Thanks to
scientific efforts is focused on the manufacturing of BRS, the wide variety of techniques and materials, 3DP can be
which are made of polymers. Depending on the type of used not only to create the final medical device but also
polymer, 3DP techniques such as FDM, MEX, DLP, SLA, in combination with other traditional manufacturing
PBF, and BJT can be used. Within this group, BJT and PBF methods to upgrade the final device: for instance, it
can be highlighted in terms of resolution. On the contrary, is possible to create patient-specific sacrificial molds,
FDM and MEX are the most frequently used and at the controlled stent coating for drug control release, etc.
same time, the ones with lower resolution [137-140] . 3DP is also a versatile technique that gives room for the
Depending on the final use of the 3D construct and the easy change and production of different geometries and
required features, the selection of materials and/or 3DP shapes that could also be of great importance to control
technique can be restrictive factors, leaving limited room or adjust the mechanical performance, degradation,
for resolution improvement. Although in some cases, the and/or drug release rate of a VS. These features can
printing resolution may not be decisive for the performance also be adapted to the requirements and needs of
of the printed structure (i.e., in dental prosthesis [141] ), we each particular patient thanks to this manufacturing
hypothesize that this factor could cause irregularities in method. Nonetheless, there are limitations and
VS that ultimately give rise to blood turbulences, let alone flaws (e.g., limited resolution and subsequent lack of
the necessity to accomplish manufacturing reproducibility manufacturing reproducibility) that must be overcome
and quality control. Post-treatment of the 3D-printed for 3DP to become a realistic VS manufacturing option.
structures have demonstrated to be a valuable option to Shape-memory polymers, though promising and easy to
improve the final resolution of the VS [137] . Computational print, lack in mechanical performance. Moreover, the
studies could also be of use in predicting or quantifying shapes of VS are rather intricate and difficult to achieve
the importance of structural changes and irregularities for with 3DP techniques such as DED or MEX due to
the performance of the VS but they would not solve the overhanging parts. The use of rotatory mandrels could
root problem. The implementation of machine learning to solve this problem but the degree of customization
3DP could shed some light in this regard, since it will be could be limited. On the other side, SMA is an option
useful not only for the design of the VS, but also in the for the manufacturing of VS, but their integration with
optimization of printing parameters and in situ printing 3DP is posing several difficulties: shape memory effect
monitoring [142-144] . is not good, and printing parameters are difficult to
optimize. The present review is concluded with a few
8. Conclusions and challenges major points:
(i) Despite the different possibilities and stent type
Medical devices such as VS have revolutionized the reviewed, the most used VS nowadays are metal-
treatment of cardiovascular diseases to the point that based, mainly because of their unbeatable mechanical
nowadays their implantation has become a routine, easily properties. On the other hand, the 3DP of these
approachable surgical intervention for the treatment of VS is one of the most challenging techniques, as
stenosed vessels, especially in CAD. Throughout the years, demonstrated by the absence of studies.
stent technology has greatly evolved, from conventional,
permanent, metallic vascular stents to the most (ii) The achievement of stents with optimal mechanical
outstanding designs such as bioresorbable, drug-eluting properties is a big challenge (even for the traditional
medical devices. In view of the wide variety of VS currently manufacturing processes), since a proper
available in the market and the intelligent approaches for compromise between axial flexibility and radial
their production, vascular stenting is considered a mature, rigidity is crucial for a proper stent patency.
consolidated medical procedure. Nevertheless, a more (iii) Computational studies and machine learning are
efficient approach is required to address several medical greatly useful for the rational design of VS, helping
and scientific challenges; most of them are related to the to accelerate the innovation of new structures and
long-term effects jeopardizing stent patency, such as in- geometrical designs as well as to minimize some
stent restenosis and thrombosis, especially PAD. Although 3DP limitations such as in resolution.
bioresorbable and drug-eluting stents seemed to shed
some light on this matter, it is still a challenge to optimize (iv) 3DP limitations can be minimized by strategically
the mechanical properties of the stent and to have a total implementing it at different points or by combining
control over the stent degradation and drug release rate. it with other manufacturing techniques.

Volume 9 Issue 2 (2023) 247 https://doi.org/10.18063/ijb.v9i2.664