Biodegradable Airway Stents Research Articles

Microinjection Molded Biopolymeric Airway Stent with Antibacterial and Anti-hyperplastic Properties.

Central airway stenosis is a condition that the diameter of trachea or main bronchus shrinkage caused by external compression or internal tissue hyperplasia, which can cause difficulty breathing, asphyxia, and even death. Airway stenting is an easy way to restore the patency of central airway, but airway stents commonly used in clinical practice can lead to complications such as mucus plugging, bacterial infection and granulation tissue hyperplasia. Moreover, the non-degradable characteristic makes it require a second operation to remove, which have the potential to cause tissue damage. In this study, a biodegradable airway stent fabricated by microinjection molding using the bioelastomer of poly (L-lactide-co-ε-caprolactone) (PLCL) as the matrix material. The airway stent has excellent mechanical properties and an appropriate degradation rate. The hydrophilic surface of the airway stent can inhibit mucus plugging. The loading of silver nanoparticles (AgNPs) and cisplatin endows the stent with antibacterial and anti-hyperplastic functions. In vitro and in vivo experiments demonstrate that this study provides an antibacterial and anti-hyperplastic biodegradable airway stent with elastic properties to avoid secondary removal operation and reduce complications associated with mucus plugging, bacterial infection and granulation tissue hyperplasia. This article is protected by copyright. All rights reserved.

In-vivo efficacy of biodegradable ultrahigh ductility Mg-Li-Zn alloy tracheal stents for pediatric airway obstruction

Pediatric laryngotracheal stenosis is a complex congenital or acquired airway injury that may manifest into a potentially life-threatening airway emergency condition. Depending on the severity of obstruction, treatment often requires a combination of endoscopic techniques, open surgical repair, intraluminal stenting, or tracheostomy. A balloon expandable biodegradable airway stent maintaining patency while safely degrading over time may address the complications and morbidity issues of existing treatments providing a less invasive and more effective management technique. Previous studies have focused on implementation of degradable polymeric scaffolds associated with potentially life-threatening pitfalls. The feasibility of an ultra-high ductility magnesium-alloy based biodegradable airway stents was demonstrated for the first time. The stents were highly corrosion resistant under in vitro flow environments, while safely degrading in vivo without affecting growth of the rabbit airway. The metallic matrix and degradation products were well tolerated by the airway tissue without exhibiting any noticeable local or systemic toxicity.

A feasibility study of biodegradable magnesium-aluminum-zinc-calcium-manganese (AZXM) alloys for tracheal stent application.

Airway obstruction conditions are relatively rarely observed in clinical settings but nevertheless, extremely challenging to handle, especially when observed in pediatric patients. Several surgical procedures, including tracheal resection, end-to-end tracheal anastomosis, and tracheoplasty, have been developed and practised of late, to treat airway obstruction. However, the clinical outcome is typically not satisfactory due to airway restenosis conditions that develop following surgery. Various types of stents are currently available for airway stenting ranging from non-degradable silicone tubes and bio-inert metallic stents (bare or coated with polymer matrix) to hybrid silicone tubes strengthened by metallic cores, but none of the stents provides the satisfactory long-term effectiveness. Therefore, there is a significant clinical need for a biodegradable airway stent that would maintain airway patency and totally degrade over time after meeting the desired objectives. The present study aims to investigate biodegradable magnesium-aluminum-zinc-calcium-manganese (AZXM) alloy as a potential tracheal stent. The new AZXM alloy was fabricated by partially replacing aliminum in commercial AZ31 alloy with calcium. The present study demonstrates that calcium preferentially segregates along the grain boundaries as intermetallic phases (Mg2Ca) and is homogeneously distributed in the magnesium matrix. The extruded AZXM alloy showed less pitting, higher corrosion resistance in Hank's Balanced Salt Solution (HBSS) compared to the as-cast and solution-treated AZXM alloys and exhibited optimized mechanical properties. In vitro cytotoxicity evaluation using human trachea epithelial cells demonstrated excellent cyto-compatibility of AZXM alloys compared to pure Mg and commercial AZ31 validated by a very preliminary rabbit in vivo tracheal model study. Preliminary results show that the approach to use biodegradable AZXM alloys as a tracheal stent is indeed promising, although further alloy processing is required to improve the ductility needed followed by a more exhaustive in vivo study to demonstrate full viability for stent applications.

Abstract P-612: BIODEGRADABLE AIRWAY STENTING – IS IT A TEMPORISING OR A LIFE-SAVING STRATEGY?

Aims & Objectives: Vondrys et al have reported their first experience with the biodegradable airway stents (BAS) in children in the United Kingdom (1). They concluded that BAS offers avoidance of both permanent stenting and short-term, expensive ventilator support. Our aim is to report our experience of airway stenting with the BAS (Ella-CS) at Alder Hey Children’s Hospital, Liverpool, UK. Methods We report the use and value of BAS (Ella-CS) in 4 ventilator dependent children with tracheo-bronchomalacia or extrinsic airway compression, aged between 3 months to 3 years admitted to a tertiary paediatric intensive care unit (PICU) in 2016 and 2017. Results After careful evaluation and work-up by a multi-disciplinary airway team, 4 patients underwent endo-bronchial stenting. Table 1 illustrates the diagnosis, procedure details and the outcome of all the 4 patients. 3 of the 4 patients were extubated and discharged out of PICU shortly after the intervention and the 4th patient had significant reduction in the ventilatory pressures. 2 of the 4 patients have been discharged home and are doing well. Figure 1 illustrates the Ella biodegradable airway stent. Figure 2 illustrates the imaging of the patient no.1 - Pre-stenting on the left and with BAS in situ on the right.Conclusions BAS are not just a temporising strategy to avoid ventilator-dependency and save expensive PICU resources, but could also be life-saving. More experience with BAS and long-term follow-up studies are essential.

Stents for airway strictures: selection and results.

Airway stents can provide effective and timely relief in patients with central airway obstruction. Silicone based stents are the most commonly used airway stents worldwide with a long track record of safety. Metallic stents continue to evolve from the earliest uncovered versions to a variety of newly designed covered stents. Despite the availability of a variety of stent materials and designs, minimal advances have been made towards innovation in stent technology and an ideal stent has unfortunately not yet been developed. Nevertheless, the first generation of biodegradable airway stents are available, work on drug-eluted stents is in the pipeline and three-dimensional printing of a customized airway stent may be the future. In this review, we discuss selection and results for most commonly utilized airway stents.

Beyond dilation: current concepts in endoscopic airway stenting and reconstruction.

To discuss current modalities of endoscopic airway management beyond balloon dilation therapy. Advances continue to be made through technology and bioengineering with exciting potential in the pediatric airway. Smaller robots and instrumentation allow increased endoscopic surgical success. Biodegradable stents and bioengineered grafts are on the horizon for use in airway surgery. Dysphonia following airway reconstruction is of increasing recognition with new endoscopic treatments being performed. Supraglottoplasty is further recognized as a treatment for obstructive sleep apnea for laryngomalacia diagnosed on sleep endoscopy. Interarytenoid injection may be beneficial in the normal larynx for aspiration and dysphagia as well as diagnosing and treating type I laryngeal clefts. Endoscopic airway surgery continues to be a popular and effective method of treating the pediatric airway. Technological advances such as in robotics may have an increasing role in the future of endoscopic airway surgery in children. Bioengineered airway adjuncts including biodegradable airway stents look to be promising in the future treatment of airway stenosis.

Effect of Mucin and Bicarbonate Ion on Corrosion Behavior of AZ31 Magnesium Alloy for Airway Stents.

The biodegradable ability of magnesium alloys is an attractive feature for tracheal stents since they can be absorbed by the body through gradual degradation after healing of the airway structure, which can reduce the risk of inflammation caused by long-term implantation and prevent the repetitive surgery for removal of existing stent. In this study, the effects of bicarbonate ion (HCO3−) and mucin in Gamble’s solution on the corrosion behavior of AZ31 magnesium alloy were investigated, using immersion and electrochemical tests to systematically identify the biodegradation kinetics of magnesium alloy under in vitro environment, mimicking the epithelial mucus surfaces in a trachea for development of biodegradable airway stents. Analysis of corrosion products after immersion test was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) was used to identify the effects of bicarbonate ions and mucin on the corrosion behavior of AZ31 magnesium alloys with the temporal change of corrosion resistance. The results show that the increase of the bicarbonate ions in Gamble’s solution accelerates the dissolution of AZ31 magnesium alloy, while the addition of mucin retards the corrosion. The experimental data in this work is intended to be used as foundational knowledge to predict the corrosion behavior of AZ31 magnesium alloy in the airway environment while providing degradation information for future in vivo studies.

Fully Biodegradable Airway Stents Using Amino Alcohol‐Based Poly(ester amide) Elastomers

Airway stents are often used to maintain patency of the tracheal and bronchial passages in patients suffering from central airway obstruction caused by malignant tumors, scarring, and injury. Like most conventional medical implants, they are designed to perform their functions for a limited period of time, after which surgical removal is often required. Two primary types of airway stents are in general use, metal mesh devices and elastomeric tubes; both are constructed using permanent materials, and must be removed when no longer needed, leading to potential complications. This paper describes the development of process technologies for bioresorbable prototype elastomeric airway stents that would dissolve completely after a predetermined period of time or by an enzymatic triggering mechanism. These airway stents are constructed from biodegradable elastomers with high mechanical strength, flexibility and optical transparency. This work combines microfabrication technology with bioresorbable polymers, with the ultimate goal of a fully biodegradable airway stent ultimately capable of improving patient safety and treatment outcomes.