Page 254 - IJB-9-2

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

the better the vascular flow. On the other hand, a greater their undefined hemocompatibility and biodegradability.
axial flexibility would bring about better adaptation of When it comes to hemocompatibility, LDHs apparently
the VS to folding or deformation and to natural curvature show a better performance than other clay minerals [122-129] .
of the native vessel, thus reducing the damage to the Nevertheless, it is also well-known that these materials
vascular wall. Finding a compromise between these two can be modified or functionalized by their combination
contradictory but coexisting features (axial flexibility with chemical ingredients to adjust their final properties
versus radial rigidity) is one of the main challenges in the and performance [130-132] . The surface functionalization or
contemporary design of stents. On top of that, it could organomodification or inorganic ingredients would enable
also be useful to fabricate stents with different mechanical the adjustment of their final properties and the reduction
properties along the structure. Both ends of the VS are the of undesirable effects that may occur. A LDH has been
most conflicting area in hyperplasia, since the damage over recently used as an ingredient of a biodegradable coating
the vessel is higher in these zones. It could be feasible using intended to be used in a DES [133] . The final aim of this
3DP and a mixture of different materials. coating was to minimize neointimal hyperplasia associated
with BMS. The drug-eluting coating consists of a PLA–
The materials and their concentration are crucial for PEG–heparin copolymer loaded with LDH–biochanin-A
the mechanical properties of the VS, and their structural composite. Biochanin A is an isoflavone phytoestrogen
design also plays an important role. In this regard, 3DP and with antiproliferative and vasculoprotective properties.
computational studies could mark a milestone since they In this particular case, LDH not only acted as carrier and
enable the study of several structural designs at the same controlled release agent, but also as a protective platform for
time (computational studies) and their rapid reproduction the drug. In addition to the full solid-state characterization
(3DP) to confirm or deny the predictions made with of the composites and the in vitro study of the release of
calculations, not to mention the possibility of adapting the both heparin and biochanin A, the protein adhesion and
designs to a particular artery, material or type of lesion. The hemocompatibility were evaluated. This study revealed
idea of some researchers to combine both strategies [70,85] is that the copolymer composite was non-thrombogenic,
promising and can be envisaged as an intelligent approach which is a positive starting point in the use of inorganic
for future directions in the research and development of VS. ingredients for the development of VS.

Ingredients such as graphene or CNT, together with In view of the number of studies using SMP for the
CIP, have been recently proposed for the development of manufacturing of VS, it is possible to state that “smart
VS through 3DP [70,99] . The use of these ingredients has been materials” have arrived to stay [134,135] . The usefulness of
mostly motivated by their already demonstrated ability to smart materials in the development of cardiovascular
reinforce materials such as polymers, together with their devices (not only VS) has been demonstrated by the number
role as drug carriers that are able to control drug release, of already commercialized VS made of nitinol (SMA), i.e.,
which also make them good candidates for the production VascuFlex® or S.M.A.R.T™ Flex, among others. Others like
of DES. Apart from graphene and CNT, similar inorganic ferromagnetic SMA are also drawing attention [135] and
ingredients such as natural and synthetic clay minerals (e.g., can also be 3D-printed. Even if much remains to be done,
montmorillonite, laponite, and layered double hydroxides especially when it comes to 3D-printed VS, it is clear that
[LDH]) also have a lot of potential in the present matter, SMP offer attractive features, from their self-expanding
acting as mechanical reinforcement [110-115] and drug delivery property to the biocompatibility, biodegradability and
systems [116-118] . The vast majority of DES are loaded with drug-eluting features, not to mention the possibility of
antithrombotic, antiproliferative, immunosuppressive, or being compatible with different 3DP techniques. The range
anti-inflammatory drugs. Nevertheless, for disorders such of future possibilities is even greater if we consider SMP
as PAD, the use of nitric oxide as an active ingredient seems functionalization, surface modifications or their use as
a reasonable candidate. In this regard, LDHs and other part of nanocomposites [106,136] .
inorganic ingredients such as zeolites can act as a persistent
and stable reaction mediator (catalyst) for the production Another important factor, which is sometimes
of nitric oxide for inhalation therapy [119-121] . This ability of overlooked, is the resolution of the final construct and how
LDH and zeolites as carriers and catalysts of nitric oxide the selection of the 3DP technique influences it. It is well-
could be potentially applied for the design of peripheral VS known that the resolution depends on a wide variety of
in the future. factors, not only on the 3DP technique itself. For instance,
different 3D printers using the same technique can have
As far as we are concerned, the use of the aforementioned strong differences in the final resolution depending on their
ingredients (montmorillonite, laponite, LDH) for the particular features (e.g., the light source of DLP or SLA
development of VS is currently scarce, probably because of 3D printers [137] ), not to mention the different resolutions

Volume 9 Issue 2 (2023) 246 https://doi.org/10.18063/ijb.v9i2.664