Liquid purification or separation – Filter – Material
Reexamination Certificate
1999-12-30
2001-06-26
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Filter
Material
C210S500350, C210S490000, C264S048000, C264S049000, C427S244000
Reexamination Certificate
active
06251276
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a leukocyte eliminating filter and a method for manufacturing the same. More particularly, this invention relates to a cationized and hydrophilized leukocyte eliminating filter which is made from a porous film, and to the manufacturing method of such a leukocyte eliminating filter, wherein the surface of the porous film is rendered to retain (through coating, for instance) a hydrophilic polymer comprising an alkylsulfate or alkylsulfonate of primary, secondary, tertiary or quaternary amine, thereby modifying the surface of the porous film so as to cationize and hydrophilize the leukocyte eliminating filter.
It is usually conducted, on the occasion of blood transfusion, to eliminate of inactivate leukocyte through a centrifugal separation, a radiation exposure or filtration for the purpose of preventing the generation of various side reactions that may be caused as a result of blood transfusion, such as the induction of GVHD (Graft Versus Host Disease) which may be brought about—mainly due to the presence of leukocyte, or for the purpose of preventing an infectious disease that may be caused by a virus-infected leukocyte. Among them, the elimination of leukocyte by means of filtration is widely adopted as it can be executed at patient's bedside because of the reasons that the method is simple and low in cost.
It is desired in the operation of eliminating leukocyte at patient's bedside to employ a leukocyte eliminating filter which is not only excellent in leukocyte eliminating capability but also capable of performing a smooth filtration. Such a leukocyte eliminating filter can be obtained by modifying the surface of the porous film constituting the leukocyte eliminating filter. This surface modification involves, in meaning, not only to render the surface to become easily adherable by leukocyte in addition to the adjustment of pore size of the porous film for the physical elimination of leukocyte, but also to render the surface to become hydrophilic.
To render the surface of the leukocyte eliminating filter to become easily adherable by leukocyte can be achieved by cationizing the surface thereof. Because, since the surface of cell such as leukocyte is electronegatively charged, it is known that, in order to eliminate the electronegative charge, the surface of the leukocyte eliminating filter is required to have positive electric charge (U.S. Pat. No. 3,242,073; and No. 3,352,424).
Further, when the surface of the leukocyte eliminating filter is rendered to be hydrophilic, blood is allowed to pass through the filter with little resistance at the moment when blood or blood preparation is contacted with the leukocyte eliminating filter, thereby making it possible to realize a smooth filtration thereof. As one of the indexes representing the hyrophilicity of the surface of filter, there is known a method of employing the critical wet surface tension thereof (hereinafter referred simply to as CWST, which will be explained below in detail).
BRIEF SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a leukocyte eliminating filter which can be easily manufactured and a method for manufacturing the filter, which can be realized through the cationization and hydrophilization of the surface of a substrate constituting the leukocyte eliminating filter for the purpose of improving the elimination of leukocyte.
It has been found as a result of intensive studies by the present inventors that the aforementioned objects can be realized by coating a leukocyte eliminating filter with a polymer having a chemical structure represented by any one of the following formulas (I) and (II), which are conventionally known as an antistatic agent, the coated polymer being subsequently heated to dry, thereby accomplishing this invention.
wherein R
1
, R
3
, R
4
, R
5
, R
6
and R
7
may be the same or different and are individually hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R
2
is CONH
2
or COOH; R
8
is an alkyl group having 1 to 12 carbon atoms; and x is an integer of 3 or 4.
DETAILED DESCRIPTION OF THE INVENTION
This invention will be further explained as follows.
The porous substrate for the leukocyte eliminating filter may be a porous body, a plane film, a hollow fiber, an unwoven fabric, a woven fabric, or a composite thereof. The porosity of the substrate should preferably be in the range of 75% to 95%, more preferably in the range of 80% to 95%, and the pore diameter thereof as measured by means of the mercury injecting method should preferably be in the range of 0.1 to 30 &mgr;m, more preferably in the range of 2 to 20 maikuro &mgr;m. The reasons for limiting features of the substrate in these ranges are as follows. Namely, if the porosity of the substrate is 75% or more, it becomes possible to minimize the filtration time, while if the porosity of the substrate is 95% or less, it becomes possible to ensure the strength of the filter. On the other hand, if the pore diameter of the substrate is less than 0.1 &mgr;m, the clogging of the filter may be easily caused during the operation of eliminating leukocyte, thus making the filter useless, while if the pore diameter of the substrate is more than 30 &mgr;m, the frequency of contact between the blood or the leukocyte in blood preparation and the filter is deteriorated, thus reducing the trapping ratio of leukocyte.
In this description, &mgr;m means micro meter.
The leukocyte eliminating filter should preferably be constructed such that the substrate itself is cationic or the surface thereof is cationized. Because, since the cell surface of leukocyte is electronegatively charged, it would become easy to trap the leukocyte, if the surface of the leukocyte eliminating filter is made cationic.
As for the substrate constituting the leukocyte eliminating filter to be employed in this invention, it is possible to employ a fibrous body or a spongy body made from a natural polymer such as cotton and hemp; a synthetic polymer such as polyester (such as PET), polyacrylonitrile, polyolefin, polyolefin halide, polyurethane, polysulfone, polyether sulfone, poly(metha)acrylate, ethylene-polyvinyl alcohol copolymer, butadiene-acrylonitrile copolymer, etc.; or a mixture thereof. In view of the workability and the compatibility with blood however, a spongy polyurethane porous body is most preferable.
However, since these substrates for the blood filter, which are represented by polyurethane for instance, are generally highly hydrophobic in nature as they are, though they can be provided with an excellent leukocyte eliminating property due to their excellent workability and blood compatibility as mentioned above, it is rather difficult for blood to smoothly pass through the pores of the fibrous or spongy body thereof, so that some sort of hydrophilization treatment of these substrates is required to be performed.
If, in this case, the hydrophilization treatment thereof can be conducted simultaneous with the cationization treatment thereof, these treatments can be accomplished once for all, thus making it possible to simplify the working process and to improve the production efficiency. According to this invention, it is now possible, through a simple operation, to improve the hydrophilicity of the substrate, and at the same time, to promote the leukocyte eliminating performance of the substrate, thus increasing the production capacity of the filter.
Followings are specific examples of coating agent to be suitably employed in this invention.
Discussing more specifically, the coating agents to be suitably employed in this invention are high molecular compounds which can be represented by the following general formulas (I) and (II).
wherein R
1
, R
3
, R
4
, R
5
, R
6
and R
7
may be the same or different and are individually hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R
2
is CONH
2
or COOH; R
8
is an alkyl group having 1 to 12 carbon atoms; and x is an integer of 3 or 4.
By the way, polymers represented by the aforementioned general f
Burns Doane , Swecker, Mathis LLP
Fortuna Ana
Terumo Kabushiki Kaisha
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