Drug-eluting stents are also called drug-releasing stents. Like drug balloons, it is an interventional therapy technology. A "stent," as the name implies, is a device that has a supportive effect. In the biomedical industry, it can be used to dilate and recanalize narrowed, occluded vessels or lumens, which is a typical implantable device.
Among the early treatment for coronary artery disease, the main problems with interventional techniques included acute postoperative occlusion (incidence 3%) and postoperative restenosis (incidence 30-50%). Thus, in the 1980s, the coronary stent was invented, which effectively reduced the acute postoperative occlusion and restenosis, but the incidence of restenosis (20-30%) still affects the efficacy of coronary interventions. Restenosis occurs because after stent implantation, the body treats the stent as a foreign body, and the area where the stent contacts the arterial membrane is treated as a traumatic area, so scar tissue proliferation will occur around the stent, and in severe cases, it may even cause restenosis or even blockage of the dredged area. Therefore, we need to use drugs to inhibit the growth of scar tissue to keep the coronary artery open. Thus combine the drugs with stents, the drug-eluting stents appear.
Figure 1. Drug-eluting stents coated by ultrasonic stent coating system
A drug-eluting stent is a stent with a specific drug coating attached to its surface. When the stent is inserted into the diseased part of the vessel, the drug it carries is slowly released by elution and takes effect in the affected area, thus preventing in-stent restenosis. Just like the material selection and structure faced by the early generation of stents, the exploration of the drug-eluting stent coating process has become a challenge for scientists. There are various coating processes, and the main processes include: stent pretreatment - drug loading - post-treatment - sterilization. Drug loading is the key to the success of the whole coating process. We have tried both physical and chemical methods to coat the stents with drugs. Physical methods includes dip coating and ultrasonic stent coating, while chemical methods mainly include electro-redox reactions between the drug and the stent surface to form the coating. Among them, the coating by electrochemical method has strong adhesion and high uniformity, but it requires the stent to be a conductor or semiconductor material. At the same time, we also need to chemically modify the drug, the process is more complex, which is difficult to achieve mass production, so this method is not commonly used. The dip coating, or immersion method, has a relatively low accuracy for drug loading and is difficult to control the uniformity of the coating. Compared with the dip coating process, the ultrasonic stent coating process has more obvious advantages for controlling the thickness and uniformity. Currently, ultrasonic stent coating technology performs well in all types of coating or thin film coating operations based on its advantages. For drug-eluting stents, ultrasonic stent coating technology not only has obvious advantages in coating uniformity, but also has high load accuracy. We can control the surface properties and coating thickness of the coating through multiple and repeated spray coating.
Figure 2.Peripheral Stents
When it comes to ultrasonic stent coating technology, Siansonic has rich experience in ultrasonic atomization technology for more than 30 years and has been contributing to the biomedical industry, providing a variety of ultrasonic stent coating products and solutions for drug coating processes in implantable and interventional medical devices. For example, the ultrasonic stent coating system UC410 and the ultrasonic drug balloon catheter coating system UC510, together with its own intellectual property ultrasonic spray nozzles, provide a full range of solutions for drug stent coatings.
