Page 244 - IJB-9-2

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

ascribed to the presence and control release of heparin. On dodecamethylene citrate), mPDC) by mixing citric acid
the other hand, the functional groups in the stent surface and 1,12-dodecanediol, THF . The photocuring process
[73]
did influence the medical device interaction with cells and transforms the initial material into a bioresorbable one,
mechanical properties. The amine-rich surface of the stent which can be used as a biomaterial ink for the production
with PDA and immobilized PEI promoted rapid smooth of VS and shows in vitro degradation of 25% (PBS, 37°C)
muscle cells (SMC) proliferation, while the opposite within 6 months. Upon deployment, the fabricated stent was
happened for the heparin-loaded stent (Figure 8B). On the able to self-expand properly, reaching the original diameter
other hand, heparin-loaded stent increased endothelial cells in just 3 min. This self-expansion was reported to be faster
(EC) proliferation (Figure 8B) and nitric oxide generation, than the expansion of other commercial BRS, taking time
which is desirable for a good patency. The combination from 3 to 8 min. Moreover, the final mechanical properties
of PLA, PDA, and PEI enhanced segmental compression, of these 3D-printed BRS were comparable to bare-metal
bending and foreshortening tests. Even if the addition nitinol stents, making them a feasible formulation for
of heparin weakened the mechanical performance, it the production of customizable, personalized BRS. Later,
enhanced the stent flexibility . More recently, a MEX 3D authors reported an in-process calibration method for the
[14]
printer has been used to obtain a BRS, photocurable, shape same micro CLIP printing process, aiming to reduce the
memory cyclodextrin-PCL-paclitaxel (βCD-PCL-PTX) total fabrication time from 70 min to 20-11 min depending
stent, which has appropriate tensile strength, elasticity, and on the layer slicing thickness of the stent . They also
[74]
bursting pressure . optimized the ingredients and concentrations during
[71]
More recently, SC-3DP has also been proposed for the printing process by including two photoinitiators:
the production of VS medical devices. As previously irgacure and ethyl 4-dimethylamino benzoate (EDAB).
emphasized, SC-3DP is considered a PBF or MEX 3DP, This combination enabled greater crosslinking and made
depending on the ingredients and the printing process. possible strut geometries.
Singh et al. used this technique to obtain a PCL-carbonyl Photocrosslinkable, elastomeric polyesters such
iron powder (CIP) stent-like structures , meaning that as metacrylated poly(dodecanediol citrate) (mPDC)
[72]
they worked with a polymeric base dissolved in an organic can be used as raw materials for the production of 3D
solvent that evaporated as extruded. No sintering is required constructs by means of DLP. mPDC polymer has proven
and debinding occurs by evaporation of the organic solvent. to be biodegradable and biocompatible and possess elastic
The authors highlighted the fact that no other previous behavior, making it suitable for the production of self-
studies have ever reported the use of this 3DP process as expandable BRS [75,76] . Oliveira et al. developed a BRS, DES
a VS manufacturing technique. Nevertheless, no VS 3D based on mPDC and nitric oxide, and used DLP as 3DP
constructs were produced, but the attention was focused technology to produce a small diameter VS (Figure 9A) .
[75]
on the effect of CIP as a PCL reinforcement as well as on With respect to other active substances, nitric oxide has
the final biological performance of the printed composite. proven to be more advantageous for stents in terms of
The role, properties and potential usefulness of CIP will be cellular proliferation, biocompatibility and restenosis.
addressed in later sections. Moreover, nitric oxide is beneficial to maintain the
muscular tonus of the vasculature under treatment, control
4.2. Vat photopolymerization 3DP as vascular stent blood pressure and inhibit platelet adhesion. Although the
manufacturing technique authors proposed this approach for a coronary stent, its
As previously mentioned, VPP 3DP techniques work with a translation into a peripheral one could be more beneficial
liquid raw material that undergoes solidification by different if blood pressure and muscle tone of the peripheral vessels
mechanisms, depending on both the material itself and the are lower with respect to coronary arteries. Moreover,
specific 3DP methodology used. For the production of VS, it has recently been demonstrated that the nitric oxide
photocrosslinkable resins and polyesters are able to provide system and its regulators are compromised in PAD .
[77]
suitable mechanical properties after curing; therefore, they Nitric oxide release was achieved by the S-nitrosation
can be used as vascular endoprothesis.
of N-acetyl-d-penicillamine (SNAP) of the 3D-printed
Micro-continuous liquid interface printing (micro construct via liquid adsorption . The self-expanding
[75]
CLIP) is a technique that works with a similar principle to properties of the stent were confirmed due to good elastic
that of DLP. The speed, reproducibility, and fidelity of this response up to 50% strain. In fact, the stent completely
3DP possess a high potential in the production of in situ, recovered its initial dimensions after being collapsed and
tailor-made BRS. Van Lith et al. used a customized micro crimped (Figure 9C). Nevertheless, the authors stated that
CLIP for the production of a photocurable, antioxidant an optimal cure is needed for the mechanical properties
and bioresorbable metacrylated biomaterial (poly(1,12- to be maximized, meaning that the DLP printing process

Volume 9 Issue 2 (2023) 236 https://doi.org/10.18063/ijb.v9i2.664