For patients with an injured or compromised trachea, the insertion of a stent is often required in order to keep their airway open. A new type of airway stent should remain in place better than others, and will biodegrade when no longer needed.
Ordinarily, airway stents are made of either silicone or metal, the latter of which can be difficult to remove once the trachea has healed. Silicone models are easier to take out, but they may gradually migrate away from the insertion site. This is because they are not specially made for each patient, so they don’t fit perfectly.
With these limitations in mind, scientists at ETH Zurich – working with colleagues from the University Hospital Zurich and the University of Zurich – have created a custom-fit biodegradable airway stent made of biocompatible silicone. The process begins with a CT (computer tomography) scan being performed on the patient’s trachea.
The resulting imagery is used to create a 3D digital model of a stent that will fit specifically into that individual patient’s throat. That model is then utilized to 3D-print the actual stent, via a process known as digital light processing (DLP). This technique involves shining a pattern of ultraviolet light into a transparent-sided vat of photosensitive resin, causing specific parts of that resin to polymerize into a solid.
In the past, biodegradable DLP-printed objects have tended to be hard and brittle. In order to make the stent soft and elastic, a special type of resin had to be created. Because that resin is too viscous at room temperature, the printing process has to take place at temperatures of 70 to 90º C (158 to 194 ºF).
The finished airway stent is flexible enough to be folded down while being inserted, subsequently popping into shape once it’s within the trachea. Particles of gold within the polymer allow the stent to be visually tracked using conventional medical imaging technology, guiding the insertion process.
In lab tests performed on rabbits, X-rays revealed that the stents generally stayed in place over a six to seven-week period, after which they were harmlessly absorbed by the body.
The scientists are now investigating methods of scaling the process up for clinical use on human patients. A paper on the research was recently published in the journal Science Advances.