Vienna: Blocked blood vessels can quickly become dangerous. It is often
necessary to replace a blood vessel – either by another vessel taken
from the body or even by artificial vascular prostheses. Together,
Vienna University of Technology and Vienna Medical University have
developed artificial blood vessels made from a special elastomer
material, which has excellent mechanical properties. Over time, these
artificial blood vessels are replaced by endogenous material. At the end
of this restorative process, a natural, fully functional vessel is once
again in place. The method has already been used successfully in rats.
Arteriosclerotic
vascular disorders are one of the most common causes of death in
industrialized countries. In this situation a bypass operation is often
the only solution. Normally, blood vessels are taken from another part
of the patient's body and used to replace the damaged vessel. Thanks to a
joint project undertaken by TU Wien and the Medical University of
Vienna, artificially manufactured vessels should be used more frequently
in future.
The most important thing is to find a suitable material.
The artificial materials that have been used so far are not ideally
compatible with body tissue. The blood vessel can easily become blocked,
especially if it is only small in diameter.
TUW has therefore
developed new polymers. "These are so-called thermoplastic
polyurethanes," explains Robert Liska from the Institute of Applied
Synthetic Chemistry of Vienna University of Technology. "By selecting
very specific molecular building blocks we have succeeded in
synthesizing a polymer with the desired properties."
A thin polymer thread spun into tubes
To
produce the vascular prostheses, polymer solutions were spun in an
electrical field to form very fine threads and wound onto a spool. "The
wall of these artificial blood vessels is very similar to that of
natural ones," says Heinz Schima of the Medical University of Vienna.
The polymer fabric is slightly porous and so, initially, allows a small
amount of blood to permeate through and this enriches the wall with
growth factors. This encourages the migration of endogenous cells. The
interaction between material and blood was studied by Martina
Marchetti-Deschmann at TU Wien using spatially resolved mass
spectrometry.
The new method has already proved very successful
in experiments with rats. "The rats' blood vessels were examined six
months after insertion of the vascular prostheses," says Helga
Bergmeister of MedUni Vienna. “We did not find any aneurysms, thromboses
or inflammation. Endogenous cells had colonized the vascular prostheses
and turned the artificial constructs into natural body tissue." In
fact, natural body tissue re-grew much faster than expected so that the
degradation period of the plastic tubes can be even shorter. Further
adaptations are currently being made to the material.