An ETH research team is using a 3D printing process to produce a new type of bioresorbable airway stent. This could greatly simplify the treatment of constrictions in the upper airways in the future.
In order to correct such constrictions, surgeons insert tubular implants, known as stents, made of medically usable silicone or metal. These implants have disadvantages: Metal stents have to be surgically removed with some effort. Silicone stents, on the other hand, migrate away from the site of insertion.
An ETH research team made up of members of the Complex Materials and Drug Formulation & Delivery groups, together with researchers from the University Hospital and the University of Zurich, has now developed an airway stent that is tailored to a patient and bioresorbable, i.e. it gradually degrades after implantation. These stents are produced using a 3D printing process from resin, which is later cured with UV light.
First, the researchers create a computer tomography of a specific section of the airways. Based on this, they develop a digital 3D model of the stent.
Until now, only stiff and brittle objects could be produced using DLP technology and biodegradable materials. The ETH researchers therefore developed a special resin that becomes elastic after exposure to light.
This resin is based on two different macro-monomers. The material properties of the object produced can be controlled by the length (molecular weight) of the monomers used and their mixing ratio, as the researchers show in their latest study in "Science Advances".
As soon as UV light hits the resin, the monomers link together and form a polymer network. As the newly developed resin is too viscous at room temperature, the researchers had to process it at temperatures of 70 to 90 degrees.
Inserting the stents required a special instrument, as the 3D-printed objects have to be inserted in a folded position. This requires that the implants cannot be bent or crushed and that they unfold perfectly at their place of insertion.
Successful tests, good prospects
The tests on rabbits carried out by the research group led by Daniel Franzen, Head Physician at the Department of Pneumology at the University Hospital Zurich, together with veterinarians, were successful. The researchers were able to show that the implants are biocompatible and that they are resorbed by the body after six to seven weeks. In addition, the inserted stents generally did not move from the site where they were implanted.
Furthermore, the processes are to be designed in such a way that production is possible at the place of use, or at least involves short supply chains. The process is still on a laboratory scale. "However, producing such stents on a large scale is a complex undertaking that we need to investigate further," says André Studart. However, the technology can be transferred relatively easily to similar medical applications. "It is hopefully only a matter of time before our solution finds its way into the clinic," says the ETH professor.
Source ETH Zurich (Peter Rüegg)
