A Review of Recent Patents on Structures Related to Tracheal Stents

Background: The trachea is an important part of the respiratory system. Long-term airway diseases and the effects of human physiological conditions can cause trachea stenosis. This will seriously affect patients’ physical health. Tracheal stents can provide durable support by means of dilating the narrowed area; they can effectively relieve the patient's breathing difficulties, which is of value that is more practical. Objective: To meet the vital requirements for better adaptation to the human airway environment and prevent complications associated with stent placement, the construction and materials of tracheal stents have been improved constantly. Methods: This paper investigates various representative patents related to the tracheal stent. The structure type, placement method and applications situation of these tracheal stents are discussed. Results: The characteristics of different types of tracheal stents are analyzed. This paper analyzes the main problems in its development. The solutions to the issues and the current and future research on tracheal stents are discussed. Conclusion: The tracheal stents are classified into metal stent, silicone stent, biodegradable stent and hybrid material stent. Further improvements are needed in the aspects of structural design, safety, applicability, biocompatibility, algorithm of drive model of tracheal stent. More related patents about tracheal stents need to be developed.

Telmisartan Loaded Nanofibers Enhance Re-Endothelialization and Inhibit Neointimal Hyperplasia

Stent implantation impairs local endothelial function and may be associated with subsequent adverse cardiovascular events. Telmisartan, an angiotensin II receptor blocker that has unique peroxisome proliferator-activated-receptor-gamma-mediated effects on cardiovascular disease, has been shown to enhance endothelial function and limit neointimal hyperplasia. This study utilized hybrid biodegradable/stent nanofibers to facilitate sustained and local delivery of telmisartan to injured arterial vessels. Telmisartan and poly(d,l)-lactide-co-glycolide (PLGA) (75:25) were dissolved in hexafluoroisopropyl alcohol and electrospun into biodegradable nanofibrous tubes which were coated onto metal stents. By releasing 20% of the loaded telmisartan in 30 days, these hybrid biodegradable/stent telmisartan-loaded nanofibers increased the migration of endothelial progenitor cells in vitro, promoted endothelialization, and reduced intimal hyperplasia. As such, this work provides insights into the use of PLGA nanofibers for treating patients with an increased risk of stent restenosis.

Biodegradable Stent with mTOR Inhibitor-Eluting Reduces Progression of Ureteral Stricture

In this study, we investigated the effect of mTOR inhibitor (mTORi) drug-eluting biodegradable stent (DE stent), a putative restenosis-inhibiting device for coronary artery, on thermal-injury-related ureteral stricture in rabbits. In vitro evaluation confirmed the dose-dependent effect of mTORi, i.e., rapamycin, on fibrotic markers in ureteral component cell lines. Upper ureteral fibrosis was induced by ureteral thermal injury in open surgery, which was followed by insertion of biodegradable stents, with or without rapamycin drug-eluting. Immunohistochemistry and Western blotting were performed 4 weeks after the operation to determine gross anatomy changes, collagen deposition, expression of epithelial–mesenchymal transition markers, including Smad, α-SMA, and SNAI 1. Ureteral thermal injury resulted in severe ipsilateral hydronephrosis. The levels of type III collagen, Smad, α-SMA, and SNAI 1 were increased 28 days after ureteral thermal injury. Treatment with mTORi-eluting biodegradable stents significantly attenuated thermal injury-induced urinary tract obstruction and reduced the level of fibrosis proteins, i.e., type III collagen. TGF-β and EMT signaling pathway markers, Smad and SNAI 1, were significantly modified in DE stent-treated thermal-injury-related ureteral stricture rabbits. These results suggested that intra-ureteral administration of rapamycin by DE stent provides modification of fibrosis signaling pathway, and inhibiting mTOR may result in fibrotic process change.

USEFULNESS OF BIODEGRADABLE STENT IN THE PREVENTION OF PANCREATIC FISTULA AFTER PANCREATIC SURGERY

INTRODUCTION Postoperative pancreatic fistula (POPF) remains the most important cause of morbidity after cephalic pancreaticoduodenectomy (PD), affecting up to one third of cases. The aim of this paper is to present a prospective single-center study with 16 patients undergoing PD in whom a biodegradable stent was placed, analyzing morbidity and mortality, the presence of POPF and the correct position and degradation time of the stent. MATERIAL Y METHODS A duct-to-mucosa end-to-side anastomosis was performed for the pancreaticojejunal anastomosis and the biodegradable stent (“Archimedes”, amg International GmbH, Germany) was placed from the pancreatic duct to the jejunum (Figure 1). The stent has a helical shape that facilitates the flow of pancreatic juice. POPF was defined as drainage fluid amylase value of > 5000 U/L on the first day after surgery. RESULTS Only one patient developed POPF in the postoperative period and it was successfully treated with interventional radiology drainage and somatostatin analogues. There was no mortality at 30 days after PD. An abdominal radiograph was performed to asses well-positioning of the stent on postoperative day 7. To evaluate the degradation after three months we used the CT scan. A complete degradation was defined as < 25% of stent length or stent fragments visible at CT. Completed degradation occurred after 3 months in all cases. CONCLUSION The use of resorbable internal pancreatic stent could be a valid alternative to prevent the development of pancreatic fistula after a pancreaticoduodenectomy.

HEPARIN AS AN ANTIBACTERIAL COATING ON BIODEGRADABLE URETERAL STENTS: EXPERIMENTAL STUDY OF BRAIDSTENT®-H

INTRODUCTION The aim of this study is to assess the effectiveness of heparin to inhibit the development of early bacteriuria as a coating for biodegradable ureteral stents. MATERIAL AND METHODS The BraidStent®-H biodegradable stent, whose heparin coating is incorporated by dip coating, was chosen for this study. Twenty-four swine were randomly divided into two groups: 12 animals underwent unilateral placement of the BraidStent®-H and 12 were fitted with a standard double-j stent (DJS). Bacteriuria is comparatively analyzed over time by consecutive urine sampling at 0, 1, 3, 6, 12, 24 and 48 hours. In addition, the concentration of heparin released in vitro in artificial urine at 0, 3, 6, 12, 24, 48, 72, 92 and 120 hours is determined via ELISA. RESULTS BraidStent®-H generates a significantly lower bacteriuria rate than a DJS at 6 and 12 hours. Heparin coating shows a significant delaying effect on the onset of bacteriuria, reaching 100% of the animals at 48 hours, compared to the DJS, which takes place at 6 hours. ELISA results reveal the presence of heparin in urine for a total of 72 hours. The coating does not affect the degradation of the device, which is completed at 6 weeks. CONCLUSIONS Heparin evidences an effective inhibition of early bacteriuria, showing its potential as an antibacterial coating for biodegradable ureteral stents. Future studies should focus on the development of long-term heparin coatings for biodegradable materials.

Initial Experience with Biodegradable Pancreatic Stents in the Prevention of Postoperative Pancreatic Fistula after Cephalic Pancreaticoduodenectomy

Background: Postoperative Pancreatic Fistula (POPF) remains the most important morbidity after pancreaticoduodenectomy. There is no consensual technique for pancreatic reconstruction and many surgeons use a transanastomotic drain. Currently, the stents used are not degradable and they can cause obstruction, stricture and pancreatitis. The use of biodegradable stents that disappear a few months after the intervention could have a role in the prevention of pancreaticojejunostomy complications. The aim of the study was to evaluate technical success of implantation and safety of newly available biodegradable stents in 16 patients undergoing cephalic duodenopancreatectomy. Materials and Methods: A single-center prospective non-randomized study was conducted with patients undergoing PD. A total of 16 patients were included. A duct-to-mucosa end-to-side anastomosis was performed for the pancreaticojejunal anastomosis and the biodegradable stent (Archimedes) was placed from the pancreatic duct to the jejunum. Results: One of the patients developed POPF, which was successfully treated with interventional radiology drainage and somatostatin analogues. Completed degradation occurred after 3 months in all cases. There was no mortality at 30 days after PD. Conclusion: Based on our experience, the use of resorbable internal pancreatic prostheses could be a valid alternative to prevent POPF after a pancreaticoduodenectomy, also avoiding the main complications related to the use of non-absorbable prostheses.