Filter medium having a limited surface negative charge for treating a blood material

An apparatus for selectively separating leukocytes from a leukocyte-containing suspension, comprising:

• a casing having an inlet side and an outlet side, said inlet side having an inlet for a leukocyte-containing suspension selected from the group consisting of whole blood, a leukocyte-containing red cell product, a leukocyte-containing platelet and a leukocyte-containing plasma product, and said outlet side having an outlet for a filtrate;
• and a main filter medium packed in said casing at a packing density of from 0.05 to 0.5 g/cm.sup.3,
• said main filter medium comprising a polymeric, porous element having, in a surface portion thereof, a negative charge and having a surface electric charge of not smaller than -30 .mu.eq/g of said polymeric, porous element, wherein said polymeric, porous element has an average pore diameter of from 1 to 100 .mu.m and a total pore volume of from 0.4 to 0.95 ml/ml of said polymeric, porous element, and wherein a sum of respective pore volumes of pores of said polymeric, porous element which have a pore diameter of from 1 to 100 .mu.m is 75% or more, based on said total pore volume.

An apparatus for separating whole blood into a blood cell product and plasma or for separating whole blood or plasma, each containing at least one preselected substance, into said at least one preselected substance and a remaining whole blood or plasma substantially free of said at least one preselected substance, comprising:

• a casing having an inlet for whole blood or plasma and an outlet for a filtrate;
• and a filter medium packed in said casing,
• said filter medium comprising a polymeric, porous element having, in a surface portion thereof, a negative charge and a surface electric charge of not smaller than -30 .mu.eq/g of said polymeric, porous element, and wherein said polymeric, porous element is a porous membrane having an average pore diameter of from 10 .ANG. to 1.0 .mu.m and having a water permeability of from 3.4 to 8,000 ml/hr/m.sup.2 /mmHg.

A method for treating a blood selected from the consisting of a leukocyte-containing suspension and plasma, which comprises contacting a blood material with a filter medium comprising a polymeric, porous element having, in a surface portion thereof, a negative charge and having a surface electric charge of not smaller than -30 .mu.eq/g of said polymeric, porous element, thereby controlling a bradykinin concentration of a contacted blood to a level not exceeding 4,000 pg/ml.