PLA coating technologies for next-generation coronary stents: dip coating, spray coating, and electrospinning

Abstract

Currently, various diseases are caused by the occlusion of ducts in the body. One of the most common and recurring solutions is the implantation of stents. This surgical intervention, called angioplasty, involves placing a stent in a blocked vessel to restore blood flow. Although early-generation stents made of metallic alloys, such as stainless steel (SS), demonstrated excellent mechanical properties, they are not biodegradable and often lead to long-term complications, including neointimal proliferation and chronic inflammation. As a result, polymeric coatings have been introduced to improve biocompatibility and serve as drug reservoirs. However, challenges remain in achieving optimal surface properties, such as uniformity, low roughness, and controlled thickness, which are critical for stent performance and hemocompatibility. This thesis examines three polymer coating techniques—dip coating, spray coating, and electrospinning—and assesses their effectiveness in meeting these requirements. The first article investigates dip coating using stainless steel (SS) substrates and evaluates the impact of process parameters on coating uniformity, roughness, and thickness. The second article introduces electrospinning as a method to create nanofibrous PLA coatings on SS stents, highlighting those process parameters involved in the impact of fiber diameter and surface coverage. The third article extends this approach to magnesium-based stents (WE43 alloy), addressing the additional requirement of controlling degradation rates for biodegradable applications. The last article focuses on spray coating, examining how variations in flow rate, spraying time, spraying distance, rotational speed, and inlet air pressure influence coating morphology. Altogether, this research provides a comprehensive evaluation of coating technologies for next-generation coronary stents, aiming to optimize surface characteristics to improve biocompatibility, mechanical performance, and degradation control.