Effects of shape and structure of a new 3D-printed personalized bioresorbable tracheal stent on fit and biocompatibility in a rabbit model

Abstract

To date, several types of airway stents are available to treat central airway obstructions. However, the ideal stent that can overcome anatomical, mechanical and microbiological issues is still awaited. In addition, therapeutic effect and self-elimination of these stents are desirable properties, which pose an additional challenge for development and manufacturing. We aimed to create a prototype bioresorbable tracheal stent with acceptable clinical tolerance, fit and biocompatibility, that could be tested in a rabbit model and in the future be further optimized to enable drug-elution and ensure local therapeutic effect. Twenty-one New Zealand White Rabbits received five different types of bioresorbable tracheal stents, 3D-printed from poly(D,L-lactide-co-ε-caprolactone) metacrylates. Various configurations were tested for their functionality and improved until the best performing prototype could undergo detailed in vivo assessment, regarding clinical tolerance, migration and biocompatibility. Previously tested types of 3D printed stents in our preliminary study required improvement due to several problems, mainly related to breakage, unreliable stability and/or migration within the trachea. Abandoned or refined pre-prototypes were not analyzed in a comparative way. The final best performing prototype stent (GSP2 (Group Stent Prototype 2), n = 8) allowed a transoral application mode and showed good clinical tolerance, minimal migration and acceptable biocompatibility. The good performance of stent type GSP2 was attributed to the helix-shaped surface structure, which was therefore regarded as a key-feature. This prototype stent offers the possibility for further research in a large animal model to confirm the promising data and assess other properties such as bioresorption.

Fig 1. 3D printing files and characteristics of five different tracheal stent groups.

Reprinted under a CC BY license, with permission from Dr. Fergal Coulter, original copyright 2021.

Fig 2. Mechanical properties of the stents with surface helix.

Compression test curves of personalized stents printed for the same rabbit with and without the surface helices. Mean + SD (n = 3).

Fig 3. Standardized measurement in CT images to quantify stent migration.

Migration was measured on lateral and dorsal views. Red Arrow indicates the rostral end of the stent.

Fig 4. A sample showing mucosal indentations formed by the helix surface structure, revealing partial loss of the epithelial layer.

Parts in between the indentations remained intact providing normal healing/remodeling of the tracheal mucosa (sample of rabbit 107.31, that was excluded from the study because of unstandardized personalization process).