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Regulating blood flow in vessels

Why someone develops an aneurysm is still mostly unclear. Doctoral researchers from the fields of Materials Science and Medicine are working together on new treatments to prevent cerebral haemorrhages.

Two researchers in a laboratory
© Julia Siekmann

Using 3D models, Mariya Pravdivtseva (UKSH, left) and Prasanth Velvaluri (CAU) simulate how their new stents influence blood flow in vessels with aneurysms.

If the walls of vessels such as brain arteries become weaker and more elastic, a kind of bulge can form in which blood collects. "Aneurysms can grow like a balloon. In the worst-case scenario, they rupture and this results in a life-threatening intracerebral haemorrhage," said Prasanth Velvaluri, doctoral researcher of Materials Science. "But they can also be fully reversed, so symptoms like headaches or eye problems do not occur at all." The 26 year old moved from India to Kiel in 2015 to do his Master’s degree. By now he has been researching new methods for treating aneurysms as a doctoral researcher in the Research Training Group "Materials for Brain". "As a child, I observed a lot at my father’s pharmacy and would really like to make a contribution to medical development." He is working on this in tandem with Mariya Pravdivtseva, a doctoral researcher at the University Medical Center Schleswig-Holstein (UKSH). Both are supervised in their doctoral degree programmes by Professors Jan-Bernd Hövener (Molecular Imaging North Competence Center, MOIN CC), Olav Jansen (UKSH) and Eckhard Quandt (CAU).

Aneurysms used to be sealed off from arteries with little clips to stop them filling with blood. The operating procedure itself was, however, not without risk. Minimally invasive interventions are an alternative in which tiny metal coils are inserted via catheters. They fill the empty space in the aneurysm and, by doing so, stop it from filling up with blood.

One of the main factors promoting aneurysm growth and rupture is the blood flow pushing an aneurysm wall.

Mariya Pravdivtseva

Now stents known as "flow diverters" are more and more used to seal aneurysms shut from the blood flow. While inserting these into the blood vessel, however, the flexible wire frameworks can get twisted. "This is what we want to prevent by using a different design of stents," said Mariya Pravdivtseva, who studied biological and chemical physics in Russia. The team plans to develop stents with tiny three-dimensional structures that allow for new functions. For example, the framework mesh could vary in thickness and have tiny features at certain points to securely anchor the stent in the blood vessel.

Working at a scale of just a few micrometres, however, makes implementation difficult. Together with a Kiel University start-up medical technology firm, Velvaluri is developing designs with ultra-thin material layers for the stents. For this, they are using shape memory alloys, which "remember" their original shape and return to it after being deformed. Stents made from these types of materials have the advantage to be easier to insert into blood vessels: they are compressed for the intervention and only when they are in the correct position in the artery do they unfold to their full size. Velvaluri researched other methods of folding the stents with Professor Richard James during his research stay at the University of Minnesota.

Velvaluri’s stent designs are being tested by his tandem colleague Pravdivtseva at the UKSH, where she develops models of blood vessels with aneurysms using a 3D printer. She places the new stents in the arteries and measures the blood flow using magnetic resonance imaging (MRI).

"One of the main factors promoting aneurysm growth and rupture is the blood flow pushing an aneurysm wall. The treatment has to prevent entering blood flow into an aneurysm. Therefore we want to test how good our stents divert the flow from an aneurysm", explained the 26 year old. MRI allows to measure the velocity of the blood at each point of the blood vessel, which we can compare before and after aneurysm treatment. She discusses her results with Velvaluri and the doctors at the UKSH to make further adaptations to the designs. During her research stay at the University of Wisconsin she was able to debate them in a big group. Pravdivtseva has not regretted her decision to move from Russia to Kiel: "I wanted to do research in the field of medicine – what I like about it is that you always keep in mind why you do this. Here I can combine this perfectly with my background in physics." Both plan to submit their doctoral theses at the end of the year.

Author: Julia Siekmann

Website of the graduate school: www.grk2154.uni-kiel.de


Research Training Group "Materials for Brain"

The aim of the international Research Training Group is to develop new materials for treating brain disorders such as epilepsy, aneurysms or tumours. At the moment 24 doctoral researchers from various disciplines are conducting research in tandem in the programme, which was set up in 2017. Workshops, coachings, stays abroad and regular conferences supplement the training, which is funded by the German Research Foundation (DFG). The second round with 11 doctoral researchers started on 1 April 2020. (jus)