Preparation, In Vitro Degradation And Application Of Decomposable Esophageal Stent

Esophageal stenosis or obstruction is a common digestive tract disease, which was divided into benign and malignant according to the patient’s conditions. At present, the coated nickel-titanium alloy stents are widely used as palliative treatment of malignant digestive tract diseases. However, this permanent stent could cause chronic esophageal injury as a foreign body in the body for a long time, which easily causes intimal hyperplasia, the inner muscular atrophy and aneurysm formation. It even leads to esophageal restenosis, endangering lives and health of the patients. Due to the insufficiency of permanent stents, its application scope is strictly limited. It is reported that patients has a relatively short life with this type of stent placement, about 3 to 10 months clinical stent placement period. For patients with benign esophageal stenosis or long life ecpeactancy, such as reflux esophagitis after esophageal chemical burns or postoperative anastomotic stenosis, getting the permanent stents is inappropriate. Balloon dilatation is widely used at present. But this method, which maintaining time is too short, needs to expand treatment repeatedly for many times. The treatment cycle lasts for 1-2 months, giving a lot of pain and without good therapeutic effect.Based on the problems existing in the permanent stents and combining with the characteristics of the treatment of benign esophageal stenosis, we designed a kind of decomposable stent which is suitable for the treatment of benign esophageal stenosis. Decomposable esophageal stent is composed of nickel-titanium memory alloy, silicone rubber, biodegradable polyester materials. Depends on the good mechanical performance of nickel-titanium memory alloy, high elasticity of silicone rubber and biodegradability of polymer, stents have the effect of expansion and support in the esophageal stenosis. After a period of time scaffolding of the degradation of material degradation, stent collapses into 3-5 pieces which are out of the body along with eating food through the digestive tract. The defect of permanent stents can be overcome and esophageal stents can be used more widely. According to clinical experts estimate, benign esophageal stenosis patients accounted for about 70%. Research and development of decomposable esophageal stent will bring the Gospel to many patients and relieve patients suffering. This work has good social benefit and broad market prospects.This article has carried on the study of synthesis, extrusion, stretching into silk technology research of polyL-lactic acid (PLLA) and its copolymer (PLGA). Material preparation process are derived, and the obtained material were characterized by FT-IR、1H-NMR and DSC. The degradation experiments of PLLA and PLGA lines was taken out in phosphate buffer solution under 37℃, which lasted for 8 weeks. Test items include:the exterior morphology (SEM), degradation liquid pH, mass loss, tensile strength, viscosity, wide Angle X-ray diffraction (XRD) and orientation degree. During eight weeks period, PLLA line did not change significantly and significant degradation of PLGA line. The properties of PLGA line were consistent with the design requirements, and it could be used to make the decomposable esophageal stent.Next, we studied the weaving, coating, connection process of the decomposable esophageal stent and tested its physical properties. Test items include:expansion point, softening point, flexibility, radial compression ratio, radial support. We completed the degradation experiments of two types of stents in phosphate buffer and artificial gastric juice. The study indicated that the physical and chemical properties of decomposable esophageal stents meet the requirement of clinical use. In two kinds of medium, PLGA scaffolds structure lost time was 6 weeks and 9 weeks respectively, consistent with 1 to 2 months treatment period of the typical benign esophageal stenosis. This provides a basis to the research of animal experiments.Finally, we established the rabbit model of esophageal stricture, and then observed the therapeutical effect and decomposition of decomposable esophageal stents in animals.All the experimental results showed that the developed decomposable esophageal stents, both retained the characteristics of metal stent radial supporting force, and also had the biodegradation. We could control the time of decomposition by adjusting the PLGA degradation rate which had already reached the clinical purpose. This provided a new method for the treatment of benign esophageal stenosis.