A flexible porous chiral auxetic tracheal stent with ciliated epithelium

Tracheal stent placement is a principal treatment for tracheobronchial stenosis, but complications such as mucus plugging, secondary stenosis, migration, and strong foreign body sensation remain unavoid-able challenges. In this study, we designed a flexible porous chiral tracheal stent intended to reduce or overcome these complications. The stent was innovatively designed with a flexible tetrachiral and anti-tetrachiral hybrid structure as the frame and hollows filled with porous silicone sponge. Detailed finite element analysis (FEA) showed that the designed frame can maintain a Poisson's ratio that is negative or close to zero at up to 50% tensile strain. This contributes to improved airway ventilation and better resis-tance to migration during physiological activities such as respiration and neck movement. The preparation process combined indirect 3D printing with gas foaming and particulate leaching methods to efficiently fabricate the stent. The stent was then subjected to uniaxial tension and local radial compression tests, which indicated that it not only has the same desirable auxetic performance but also has flexibility sim-ilar to the native trachea. The porous sponge facilitated the adhesion of cells, allowed nutrient diffusion, and would prevent the ingrowth of granulation tissue. Furthermore, a ciliated tracheal epithelium similar to that of the native trachea was differentiated from normal human bronchial primary epithelial cells on the internal wall of the stent under air-liquid interface conditions. These results suggest that the designed stent has the potential for application in the treatment of tracheobronchial stenosis. Statement of significance In this study, a new flexible porous chiral auxetic tracheal stent with ciliated epithelium was developed. Its auxetic properties provide a larger ventilation cross-sectional area and greater anti-migration force. It is also compatible with the tracheal growth of pediatric patients. It is flexible enough to reduce foreign body sensation and can be compressed for stent delivery. The stent can be optimized for each patient using indirect 3D printing. The porous sponge filler prevents granulation tissue ingrowth and provides a suitable environment for epithelial cells. The ciliated epithelium on the inner wall of the stent is expected to have a clearing function similar to the native trachea. This flexible auxetic tracheal stent provides new opportunities and insights into the treatment of tracheobronchial stenosis. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

A flexible porous chiral tracheal stent was developed to address complications in tracheobronchial stenosis treatment. The innovative design showed improved ventilation, resistance to migration, and compatibility with pediatric patients. The stent's auxetic properties and porous sponge filler provide a promising environment for epithelial cell growth and potential for enhanced treatment outcomes.