Despite advances in stent design, expansion techniques and anti-thrombotic agents to improve pharmacological control of subacute thrombosis (SAT) and to reduce to 2 the occlusive thrombosis rates, a significant risk of mortality associated with thrombotic vascular occlusion due to the adhesion of blood constituents remains a problem for patients with more complex lesions. The adhesion process is greatly governed by the surface characteristics, mainly the surface chemical composition, surface morphology, presence of charge, surface wettability and surface roughness. Surface chemical inertness (reduced interaction with chemicals and biological components) subsequently became the primary criteria which guided the development of non thrombotic stents as well as other blood-contacting materials. A number of strategies have been adopted in an effort to coat the stent with or without the use of a drug delivery system, to overcome the thrombus formation, to minimize the stent occlusion and to improve the overall hemocompatibility of the device. This paper aims at reviewing the clinical outcomes of main nonpharmaceutical stent coating procedures and their clinical outcomes. New stents which combine the anti-thrombotic coating with the drug delivery ability, such as radioactive stents, degradable stents and some new challenging trends which are mostly at research and development stage for stent surface coatings are also introduced.

Membrane-covered Express2TM Monorail® stents composed of chitosan (CH) blended with polyethylene oxide (PEO) in 70:30% wt (CH-PEO) were coated with a monolayer of hyaluronic acid (HA). This significantly improved the resistance to platelet adhesion and demonstrated excellent mechanical properties, resisting the harsh conditions during stent crimping and subsequent inflation. CH-PEO/HA membrane was then combined with a paclitaxel (Pac) delivery system via three different approaches for comparison of release profiles of Pac. The activity of Pac in these systems was confirmed since its presence in the membrane significantly decreased cell viability of U937 macrophages. Presented results are promising for applications requiring different release patterns of hydrophobic drugs.