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Artificial blood vessels made on a 3D printer may soon be used for transplants of lab-created organs.

Until now, the stumbling block in tissue engineering has been supplying artificial tissue with nutrients that have to arrive via capillary vessels.

A team at the Fraunhofer Institute in Germany has solved that problem using 3D printing and a technique called multiphoton polymerisation.

The findings will be shown at the Biotechnica Fair in Germany in October.

Out of thousands of patients in desperate need of an organ transplant there are inevitably some who do not get it in time.

In Germany, for instance, more than 11,000 people have been put on an organ transplant waiting list in 2011 alone.

To make sure more patients receive these life-saving surgeries, researchers in tissue engineering all over the globe have been working on creating artificial tissue and even entire organs in the lab.

But for a lab-made organ to function, it needs to be equipped with artificial blood vessels - tiny and extremely complex tubes that our organs naturally possess, used to carry nutrients.

Numerous attempts have been made to create synthetic capillaries, and the latest one by the German team seems to be especially promising.

"The individual techniques are already functioning and they are presently working in the test phase; the prototype for the combined system is being built," said Dr Gunter Tovar, who heads the BioRap project at Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart.

Elastic biomaterials

3D printing technology has been increasingly used in numerous industries, ranging from creating clothes, architectural models and even chocolate treats.

But this time, Dr Tovar's team had a much more challenging printing mission.

To print something as small and complex as a blood vessel, the scientists combined the 3D printing technology with two-photon polymerisation - shining intense laser beams onto the material to stimulate the molecules in a very small focus point.

The material then becomes an elastic solid, allowing the researchers to create highly precise and elastic structures that would be able to interact with a human body's natural tissue.

So that the synthetic tubes do not get rejected by the living organism, their walls are coated with modified biomolecules.

Such biomolecules are also present in the composition of the "inks" used for the blood vessel printer, combined with synthetic polymers.

"We are establishing a basis for applying rapid prototyping to elastic and organic biomaterials," said Dr Tovar.

"The vascular systems illustrate very dramatically what opportunities this technology has to offer, but that's definitely not the only thing possible."