Liquid purification or separation – Filter – Material
Reexamination Certificate
2000-04-10
2002-02-19
Szekely, Peter (Department: 1714)
Liquid purification or separation
Filter
Material
C210S500230, C210S500410, C523S122000, C524S041000, C525S181000, C525S189000, C525S453000, C525S535000, C525S540000, C528S171000, C528S174000, C528S401000
Reexamination Certificate
active
06348152
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a medical material containing fluorinated polysulfone having excellent in antithrombogenic properties. More particularly, the present invention relates to a medical material for use in contact with blood, suitable for a hollow fiber membrane for artificial kidneys or the like, the material containing a polysulfone having fluorine atom(s) and polyalkyl ether unit(s).
BACKGROUND ART
Synthetic polymer materials have been widely used for medical materials including artificial organs and catheters in recent years. Typical materials thereof include hydrophobic polymers such as polyesters, polyvinyl chloride, polystyrene, silicone resins, polymethacrylic esters and fluorine-containing resins and hydrophilic polymers such as polyvinyl alcohol, polyether urethanes (segmented polyurethanes, SPU), poly(2-hydroxyethyl methacrylate) and polyacrylamide as medical polymer materials. Most of the conventional materials have mainly attracted attention to physical and mechanical characteristics and have been used; however, SPU is known for its relatively excellent antithrombogenic properties.
Meanwhile, along with the progress of medical technologies, there have been more and more chances for materials to contact with biotissues or blood, and great problems about the bioaffinity of the materials have been caused. Particularly, the adsorption of biocomponents such as proteins and blood corpuscles on material surfaces and denaturation thereof not only cause normally unrecognized adverse effects such as thrombogenesis or inflammatory reactions on the side of living bodies but also are related to degradation of the materials. Therefore, these are important problems of medical materials which must be fundamentally and urgently solved. As for the prevention of blood coagulation on the material surfaces, blood anticoagulants represented by heparin have hitherto been continuously administered. Effects of long-term administration of the heparin (side effects such as hepatopathy, e.g. lipid dysbolism, prolonged bleeding time or allergic reactions), however, have become problems in recent years. Particularly, the development of blood contacting materials without requiring anticoagulants has been strongly desired for hemodialysis therapy for patients suffering from chronic renal failure and undergoing blood purification such as hemodialysis or hemofiltration.
At present, more than 100,000 patients undergo a blood purification in Japan. The principle of the blood purification is based on the contact of blood through a membrane with a dialyzing fluid, diffusion and removal of waste products or metabolites in the blood into the dialyzing fluid and further removal of excessive water by utilizing a pressure difference. A blood purifier is used when purifying the blood. The blood purifier comprises a blood circuit of bundled hollow fibers stored in a housing and has a structure for making the blood flow through the interior of the hollow fibers and the dialyzing fluid through the exterior thereof. Regenerated cellulose membranes, especially the regenerated cellulose membranes produced by a cuprammonium method have heretofore been widely used as a dialysis membrane material for the blood purifier and have played a great role in the prolongation of the life and rehabilitation of patients suffering from renal failure along with the progress in a dialysis apparatus or dialytic technologies. This is due to nothing but the fact that the regenerated cellulose membranes have excellent dialysis performances and mechanical strength and further high safety supported by the results of actual long-term use. On the other hand, in spite of progress made in hemodialysis therapy, various problems caused by the dialysis remain yet unsolved in fact. One of the main problems is temporary leukopenia due to the activation of complements contained in blood by a cellulose polymer. Another is various side effects regarded as being caused by long-term administration of a large dose of anticoagulants. As described above, blood anticoagulants typified by heparin have been continuously administered in order to suppress a blood coagulation reaction in a blood purifier when carrying out the hemodialysis. However, under the current circumstances where the solute removal performances of the blood purifier have been improved and the prolongation of life even to 20 years is now possible, problems caused by the use of the heparin have successively been pointed out. Particularly, it is revealed that the long-term administration of the heparin causes complication of side effects such as hepatopathy, e.g. lipid dysbolism, prolonged bleeding time or allergic reactions. From the point of view, the development of a blood purifier which-reduces the amount of anticoagulants used or which does not cause blood coagulation even without the use thereof at all during the blood purification therapy, i.e. the blood purifier having antithrombogenic properties has been ardently desired. Furthermore, the antithrombogenic blood purifier enables the portable use of the whole apparatus, promotes the rehabilitation of a patient confined to the hospital for about 5 hours, 2 to 3 days a week and is connected with an enhancement of his or her quality of life.
Several methods have been proposed for suppressing the activation of complements or improving the antithrombogenic properties without impairing other excellent performances of the regenerated cellulose membrane. For example, as for the suppression of the activation of complements, reports have been made of methods for fixing a polymer having a tertiary amino group onto the surface of the membrane, a method for grafting a hydrophilic polymer such as a polyethylene oxide chain onto the surface thereof by covalent bonding or the like, and effects on the suppression of the activation of complements to some extent have been confirmed. The methods, however, are still insufficient in terms of the suppression of blood coagulation (antithrombogenic properties), and there are many problems in aspects of an increase in cost due to complicatedness of methods for fixing and difficulties in obtaining of homogeneous fixed surface layers. The methods have not yet been put to practical use (for example, Japanese Laid-Open Patent Application No. 51-194/1976 and Japanese Laid-Open Patent Application No. 54-77497/1979).
All the above hydrophobic polymer materials such as polyvinyl chloride or polymethacrylic esters and hydrophilic polymer materials such as polyvinyl alcohol or poly(2-hydroxyethyl methacrylate) are not satisfactory in terms of mechanical strength, bioaffinity or the like.
Although the segmented polyurethanes suppress the adhesion of platelets by a micro-phase separation structure between a hard aromatic urethane bonding site and a soft polyether bonding site, the effects are not always sufficient. Particularly, since a partial structure of hydrogen bonding such as urethane bonding or urea bonding has strong interaction between polar groups of the main chain though it contributes to an improvement in rigidity of a molecular chain, the hydration of water molecules capable of reducing the hydrophobic interaction is inhibited. Therefore, it has been reported that the denaturation of proteins is induced and the adhesion of platelets is promoted when the proteins contained in blood are adsorbed. Generally speaking, polar sites such as hydroxyl groups or amino groups naturally induce the activation of complements (the second route) in contact with blood and provide a factor in thrombogenesis due to the promotion of fibrin ation.
Furthermore, it has recently been reported that a membrane comprising synthetic polymers such as a polysulfone or a polyether sulfone are more improved in blood compatibility such as suppression of the activation of complements than that of regenerated cellulose membranes. The antithrombogenic properties, however, are insufficient, and a reduction in the use of anticoagulants does not result.
A cellulose triacetate membrane which is a semisynthetic polyme
Kawaguhi Takeyuki
Kawahara Hiroaki
Ohmori Satoru
Sughrue Mion Zinn Macpeak & Seas, PLLC
Szekely Peter
Teijin Limited
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