Hollow fiber membranes for blood purification

A specially developed plasma process enables the production of hollow fiber membranes that permit single-stage dialysis. The hollow fibers are functionalized in such a way that the sensitive blood cells are washed unhindered through the unmodified lumens of the hollow fibers. The blood plasma, on the other hand, is filtered through the pores of the membrane. Their surface is functionalized in such a way that inflammatory endotoxins such as lipopolysaccharides (LPS) adhere to it. The new process puts considerably less strain on the patient because a substantially smaller part of the blood volume is located outside the body than in the conventional two-stage blood purification process.

Central feature of the new blood purfication process is a novel separating membrane module which is composed of a bundle of hollow fiber membranes. In the main channels, blood is separated size-selectively into plasma and platelets: the sensitive blood cells remain in the blood-tolerant lumen, while the blood plasma is flowing through narrow pores into the highly porous, nanoscale part of the hollow fibers. While flowing through the pores, the blood passes over 500 m2 of bioactive surface on which selective receptor molecules specifically and rapidly extract the toxins from the blood plasma. After this membrane passage, the toxin-free plasma is recombined with the blood cells.

For achieving such a selective membrane structure the nanopores have been provided with functional groups by a dry chemical plasma procedure and lined with the bioactive molecules in a subsequent wet chemical treatment. These molecules are fixed only in the pores and outside not inside of hollow fiber. The spatial separation protects the blood cells to be activated and thus ensures an unchanged blood-cell count.

With this new membrane, the blood cell separation and plasma cleansing are carried out in a single step. This would make it easier to handle the apheresis and the smaller amount of equipment required would allows costs to be reduced dramatically.