Washing the blood

Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology in Germany are working on developing a new method to fight blood poisoning.

In the US, over 200,000 people die from blood poisoning annually. So finding more efficient ways to fight blood poisoning is vitally important.

Present methods that are used for blood cleansing – or apheresis – involve the filtering of bacterial toxins – endotoxins – from the blood. The procedure involves drawing the blood from the patient with a hypodermic needle, and using a plasma filter to separate the blood cells and plasma.

In a second step, the plasma is percolated through microbead columns where specific absorbers remove the toxins. The plasma, now clean, is remixed with the blood cells and injected back into the patient. To prevent clotting, contact between the blood cells and the absorber surface must be avoided.

Although the approach works, it has the disadvantage that it requires costly equipment and specially trained personnel.

Now, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) in Stuttgart, are looking to change this situation.

In a project funded by the German research ministry, the IGB scientists are collaborating with colleagues from Stuttgart and Gambro Dialysatoren to develop a novel hollow fibre membrane for blood cleansing.

The ingeniously designed hollow fibre membrane in the new system is made from a blood compatible polymer that does not react with the blood cells and therefore does not cause coagulation. The absorption sites that bind the toxins are located in the extremely fine pores of the membrane and its outer surface.

As the blood is forced through the hollow fibres under pressure, only the plasma is able to penetrate into and through the fine pores – the sensitive blood cells are too large and remain in the central cavity. In this way, the blood is automatically separated.

Special binding molecules grafted in the fine pores and the outside surface remove the toxins from the liquid. The toxin free plasma is then remixed with the blood cells.

“The unique aspect of our process is that the separation of the blood cells and the cleaning of the plasma occur in one step,” explained Dr. Michael Muller of the IGB, “simplifying the apheresis procedure”.