Blood fractionation system and method

A blood filtration system comprising:

• blood supply means for supplying a liquid suspension containing a cellular blood constituent;
• a permeable filter structure rotatable about an axis and including (a) an outer surface having a microporous filter membrane sized to selectively pass only a predetermined part of said suspension and (b) an inner passage for conducting the filtered said predetermined part out of said filter structure;
• a stationary housing disposed about the outside of said filter structure to define an annular gap therebetween having a radial dimension larger than about 0.0155 inch and less than about 0.037 inch;
• said stationary housing having (a) a liquid inlet port connectable to said blood supply means to admit said liquid suspension into said annular gap at a first location and (b) a liquid outlet port disposed to output liquid from said annular gap at a second location axially spaced apart from said first location;
• and
• drive means coupled to rotate said filter structure at a speed sufficient to create a shear rate, defined as the relative surface velocity of the filter membrane divided by the radial gap dimension, in excess of about 1,000 sec.sup.-1 but less than about 12,000 sec.sup.-1.

A blood filtration method for use in performing the separating function in a system operable (1) to extract blood from an individual (2) to separate the extracted blood into a plasma constituent and a remaining constituent and (3) to return the remaining constituent to the individual, said blood filtration method comprising the steps of:

• feeding whole blood a a feed rate of about 100 milliliters per minute or less into an annular gap of a gap size of between 0.0155 and 0.035 inch defined between the interior periphery of a stationary housing structure and the exterior periphery of a rotating structure, the exterior one of which peripheries is formed by filter membrane means having a pore size on the order of 0.6 .mu.m and an effective filter area of about 50 square centimeters are less,
• rotating said rotating structure at a rate sufficient to establish movements within the blood directed into the annular gap so as to cause a plasma constituent of the blood moving in contact with the filter membrane means to pass therethrough at a rate of about one millimeter per minute per square centimeter of effective filter membrane means area and the blood cells of remaining constituent to be substantially free of shear damage such as hemolysis,
• collecting the plasma constituent passing through the filter membrane means, and
• discharging from the annular gap a remaining constituent of the blood from which the plasma constituent has been removed by filtration through the filter membrane means.

A blood filtration method comprising:

• providing a liquid suspension including at least one predetermined blood constituent subject to potential deterioration by shear damage such as hemolysis if physically abused;
• passing said liquid suspension into a predetermined gap between a rotating filter membrane means and an inside wall of a stationary housing and passing liquid from said gap at an axially spaced apart location;
• said filter membrane having pore openings sized to pass only a predetermined part of said liquid suspension thus removing at least some of said predetermined part from said liquid suspension as it passes axially along said gap while leaving said predetermined blood constituent within said gap;
• and
• rotating said filter membrane at a predetermined surface velocity relative to said stationary housing;
• said predetermined annular gap and said predetermined surface velocity being effective to continuously replenish the supply of said predetermined part adjacent said filter membrane while simultaneously substantially preventing the accumulation of said predetermine blood constituent on the filter membrane and while also simultaneously preventing substantial shear damage such as hemolysis damage to said predetermined blood constituent.

A blood filtration method comprising:

• supplying a liquid suspension containing a cellular blood constituent;
• rotating a microporous filter structure about an axis within a stationary housing with an outer filter surface having a porous filter membrane sized to selectively pass only a predetermined part of said suspension spaced from said housing to define an annular gap having a rdial dimension larger than about 0.0155 inch and less than about 0.037 inch;
• passing said liquid suspension into said annular step at a first location and outputting liquid from said annular gap at a second location axially spaced apart from said first location;
• rotating said filter structure at a speed sufficient to create a shear rate, defined as the relative surface velocity of the filter membrane divided by the radial gap dimension, in excess of about 1,000 sec.sup.-1 but less than about 12,000 sec.sup.-1 ;
• and
• conducting the filtered said predetermined part out of an inner passage of said filter structure.

A system providing means for separating filtrate from a fluid suspension having at least one biological cellular component that is characterized by having a nonrigid cell membrane free of a rigid outer cell wall, the cellular component being thereby subject to trauma when stressed, the system comprising:

• a housing body having a hollow interior and an inner surface;
• rotor means rotatable within the interior of the housing body, the rotor means having an outer surface spaced from the inner housing surface to define a gap therebetween;
• means for supplying the fluid suspension into the gap;
• a microporous filter membrane attached to the rotor means for common rotation therewith, the filter membrane having pore openings sized to separate filtrate from the fluid suspension, leaving within the gap a concentrated suspension containing the at least one cellular component that is subject to trauma;
• and
• means rotating the rotor means at a selected surface velocity, taking into account the size of the gap, being operative to create movement of the fluid suspension within the gap without substantial trauma to the cellular component for inducing transport of the cellular component outwardly from the membrane while the fluid suspension is transported to the membrane.

A system providing means for separating filtrate from a fluid suspension having at least one cellular blood component that is subject to trauma when stressed, the system comprising:

• a housing body having a hollow interior and an inner surface;
• rotor means rotatable within the interior of the housing body, the rotor means having an outer surface spaced from the inner housing surface to define a gap therebetween;
• means for supplying the fluid suspension into the gap;
• a microporous filter membrane attached to the rotor means for common rotation therewith, the filter membrane having pore openings sized to separate filtrate from the fluid suspension, leaving within the gap a concentrated suspension containing the at least one cellular blood component that is subject to trauma;
• and
• means rotating the rotor means at a selected surface velocity, taking into account the size of the gap, being operative to create movement of the fluid suspension within the gap without substantial trauma to the cellular blood component for inducing transport of the cellular component outwardly from the membrane while the fluid suspension is transported to the membrane.

A system providing means for filtering from a liquid suspension a biological cellular component characterized by having a nonrigid cell membrane free of a rigid outer cell wall, the cellular component being thereby subject to trauma when stressed, the system comprising

• a housing body having a hollow interior and an inner surface;
• rotor means rotatable within the interior of the housing body, the rotor means having an outer surface spaced from the inner housing surface to define a gap therebetween in the range of approximately 0.0155 inch to 0.037 inch;
• means for supplying the fluid suspension into the gap;
• a microporous filter membrane attached to the rotor means for common rotation therewith, the filter membrane having pore openings sized to separate filtrate from the fluid suspension, leaving within the gap a concentrated suspension of the cellular component;
• means rotating the rotor means at a selected surface velocity, taking into account the size of the gap, that is approximately that provided by rotating a one inch diameter body about its axis at 3600 rpm (3600.times.1.0.times..pi./60=188.5 inches per second), or higher, for inducing transport of the cellular component outwardly from the membrane while the fluid suspension is transported to the membrane without causing substantial trauma to the cellular component;
• component outlet means for conveying the concentrated suspension from the gap;
• and
• filtrate outlet means for conveying the filtrate from the housing.

A device providing means for filtering a desired cellular blood component from a liquid suspension comprising

• a housing body having a hollow interior and an inner surface;
• rotor means rotatable within the interior of the housing body, the rotor means having an outer surface spaced from the inner housing surface to define a gap therebetween in the range of approximately 0.0155 inch to 0.037 inch;
• means for supplying the fluid suspension into the gap;
• a filter membrane attached to the rotor means for common rotation therewith, the filter membrane having pore openings sized to separate filtrate from the fluid suspension in response, leaving within the gap a concentrated suspension of the desired cellular blood component that is subject to trauma;
• magnetic drive means on the rotor means operable in response to a magnetic field external to the housing for rotating the rotor means at a selected surface velocity of at least in the order of that provided by rotating a one inch diameter body about its axis at 3600 rpm (3600.times.1.0.times..pi./60=188.5 inches per second), while exerting a shear rate less than about 15,000 sec.sup.-1 ;
• component outlet means for conveying the concentrated suspension from the gap;
• and
• filtrate outlet means for conveying the filtrate from the housing.

A system providing means for washing foreign matter from a biological cellular component characterized by having a nonrigid cell membrane free of a rigid outer cell wall, the cellular component being thereby subject to trauma when stressed, the system comprising:

• a housing body having a hollow interior and an inner surface;
• rotor means rotatable within the interior of the housing body, the rotor means having an outer surface spaced from the inner housing surface to define a gap therebetween;
• means for supplying the cellular component into the gap;
• means for supplying a washing solution into the gap;
• a microporous filter membrane attached to the rotor means for common rotation therewith, the filter membrane having pore openings sized to pass the washing solution and the foreign matter suspended therein, leaving within the gap the cellular component essentially free of the foreign matter;
• and
• means rotating the rotor means at a selected surface velocity, taking into account the size of the gap, being operative to create movement of washing solution within the gap for inducing transport of the cellular component outwardly from the membrane while the fluid suspension is transported to the membrane without causing substantial trauma to the cellular component.