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

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.