|Fraunhofer scientists are developing a coating to enable tracheal stents to remain in position.|
A constricted trachea could require surgery to insert a stent. However, the stent can slip out of position, leading to complete closure of the windpipe. To prevent this dangerous condition, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB (Stuttgart, Germany) are developing a surface coating to keep the stent in place.
A variety of complications can affect tracheal stent placement. First, they can shift, partially or completely obstructing the respiratory tract. Second, bacteria can colonize the stent and trigger pneumonia. “The windpipe has an important barrier function, with goblet and cilia cells purifying the inhaled air," explains Martina Hampel, a scientist at IGB. "It is very important that cells like these can adhere to the stents so as to maintain the air-purifying effect of the damaged section of the windpipe and to promote incorporation of the stents in the surrounding tracheal tissue.
Together with Thorsten Walles, head of the department of thoracic surgery at the University Hospital of Würzburg and a visiting scientist at the IGB, Hampel and her team took part in a project to develop surface coatings that enable the stents to be incorporated into the surrounding tissue, reducing the risk that they will move. They used stents lined with a polyurethane (PU) film.
In the ensuing tests, a variety of different coatings were applied to the PU film. In addition to synthetic polymers composed of organic acids, the researchers experimented with biological proteins such as fibronectin and type-I collagen. The coating was then modified using plasma technology with vacuum-ionized gas. For control purposes, the experts used an untreated PU film.
“In order to find out which of the surface coatings was the most suitable, we brought both lab-cultivated cell lines and human primary tracheal epithelial cells into contact with the films in cell culture vessels," Hampel says. "What we wanted, of course, was for the primary respiratory cells from human tissue to attach themselves to the film. The researchers achieved their best results with the protein-coated film, on which the primary tracheal epithelial cells grew particularly well. “The respiratory cells proved to be more vital on bioactive films rather than on ones treated with plasma. By contrast, polymer-coated film turned out to be completely useless,” Hampel adds.
The laboratory tests have been completed, and animal tests are in preparation. If the good lab results are confirmed in these tests, the next step will be to conduct clinical trials of the modified stents. “We hope that within just a few years, our well-tolerated, cell-compatible surface coatings will be used for other biomedical prostheses such as pacemaker leads, tooth implants, and replacement joints,” Hampel comments.