Tissue Stents (Bio Stents): Search For Non- Metallic Stent And Can It Be A Game Changer In Cardiovascular Interventions?

Abstract

Coronary and Vascular stenosis poses great challenge in terms of cardiovascular disease burden.
Evolution of metallic stents has been key in treating Coronary Artery Disease both acute and chronic and
has met challenges successfully. The last 2 decades have seen substantial reform in technology, bringing
second and third generations of coronary and vascular stents mainly metallic drug-eluting stents (DES).
Though stent related stenosis is big challenge, DES has met relatively much success especially during
initial years. DES are found to be associated with good first-year outcomes but subsequent risk of stentrelated
adverse events like thrombosis, myocardial infarction, restenosis usually appear after 1 year
following implantation. The pathogenesis of these late events is related to the permanent presence of
the metal stent frame or polymer within coronaries. Besides intimal hyperplasia, late stent thrombosis,
and noncompliance with DAPT are still major issues leading to stent failure and often the need for
reintervention. As an effective alternative to metallic stents, Bioresorbable scaffolds were developed
to provide drug delivery and mechanical support functions similar to metallic drug-eluting stents
(DES), followed by complete resorption with recovery of vascular structure and function, potentially
improving very late clinical outcomes. A first-generation bioresorbable scaffold demonstrated to be no
inferior to a contemporary metallic drug-eluting stents for overall 1-year patient-oriented and deviceoriented
outcomes. However, increased rates of scaffold thrombosis and target vessel-related myocardial
infarction were noted subsequently at 5 year follow up. Tissue/Bio Stents can present as a path breaking
alternative approach to avoid intimal hyperplasia. They are characterised by presence of biodegradable
struts with tissue mesh and complete absence of metal preventing ingrowth of the neointimal tissue into
the lumen. Currently used stent materials include mainly metals and synthetic polymers. Their main
limitation is lack of hemocompatibility, which can induce thrombosis and ultimately reocclusion, thus
impairing the long-term performance of these devices. We are proposing use of biologically derived
material to overcome this issue with the aim of enhancing the biocompatibility and the capability of this
type of stents to support endothelialilzation. The aim of this article is to give a comprehensive overview
of the manufacturing and applications of Tissue or Bio Stents as well as the different strategies followed
for their development from the perspective of the material selection, fabrication approaches, and logical
validation of the different concepts into animal and clinical trials.