Ureteral stent technology:Drug-eluting stents and stent coatings

Ureteral stents are commonly used following urological procedures to maintain ureteral patency.However,alongside the benefits of the device,indwelling stents frequently cause significant patient discomfort(pain,urgency,frequency)and can become encrusted and infected.The importance of these sequelae is that they are not only bothersome to the patient but can lead to significant morbidity,urinary retention,ureteral damage,recurrent infections,pyelonephritis and sepsis.When these problems occur,stent removal or replacement alongside antibiotic,analgesic and/or other symptom-modifying therapies are essential to successfully treat the patient.In an attempt to prevent such morbidity,numerous approaches have been investigated over the past several decades to modify the stent itself,thereby affecting changes locally within the urinary tract without significant systemic therapy.These strategies include changes to device design,polymeric composition,drug-elution and surface coatings.Of these,drug-elution and surface coatings are the most studied and display the most promise for advancing ureteral stent use and efficacy.This article reviews these two strategies in detail to determine their clinical potential and guide future research in the area.

Development of nano t-PA gene coating stent and its preventive effect on dog coronary artery stent thrombosis

Background The regulation of t-PA gene is the essence and core of thrombosis. Therefore, the present study aimed to prepare nano t-PA gene coated stent and to observe its effect on coronary stent thrombosis in dogs.Methods Highly expressed t-PA gene plasmid was constructed and albumin nano t-PA gene coating stent was prepared. The major branch vessels of dog coronary artery were pre-expanded with a 3.0 mm×20 balloon with 8-10 atmospheric pressure. 10 dogs of the control group were implanted with bare metal stent; while 12 dogs of the experimental group were implanted with nano t-PA gene coating stent. Both groups were not given anti-coagulation treatments. Blood samples were taken for t-PA and D-dimer before the operation, at 1,2,4 and 8 weeks after operation. Pathological analysis found thrombosis in the cavity and the hyperplasia of the intima. t-PA expression was detected by immunohistochemical indirectly, and the thickness of the intima of the section cross was directly measured by morphometry. Liver, heart, kidneys and lung were taken for pathological observation. Results All experimental animals survived at postoperative 8 weeks. Vascular stent thrombosis was seen in 10 cases of the control group with the thrombosis rate of 100%; while was seen in 2 cases among 12 cases of the experimental group with the thrombosis rate was 16.67%（P=0.00087）. Immunohistochemical staining showed that the positive t-PA gene transfection of the experimental group was mainly distributed on the surface of hyperplasia intima, and vascular wall t-PA expression of the control group was negative. Positive t-PA signal was not found in the liver,heart, kidneys and lung. Conclusion Nano t-PA gene vector coating stent can effectively express t-PA in vascular wall and effectively prevents stent thrombosis.