Note: Descriptions are shown in the official language in which they were submitted.
DEVICE ~ND METHOD FOR SEPi~TING PLASII~ FROl~
A BIOLOGIC~ FLIJID
Technical Field
The present invention concerns a device and
method for separating plasma from a biological fluid
such as blood.
Backqround of th~ Invention
An adult human contains about 5 liters of
blood, of which red blood cells account for about
45~ of the volume, white cells about 1%, and the
balance being li~uid blood plasma. Blood also
contains large numbers of platelets. In view of the
suhstantial therapeutic and monetary value of blood
components such as red blood cells, platelets, and
plasma, a variety of techniques have been ~eveloped
to separate blood into its component fractions while
ensuring maximum purity and recovery of each of the
- components.
A non-c~ntrifugal technique for separating a
biological fluid into one or more components is by
passing the biological fluid through a separation
device. Typically the separation device includ~s a
porous membrane or thP like which allows at least
one component of the biological fluid to pass
~hrough the membrane while the remaining components
of the fluid pass over or tangentially to the
~embrane. For example, whole blood or platelet-rich
plasma may be directed into a separation device
which allows a non~cellular component such plasma to
~ass through the membrane.
As wlth many biological fluid proc2ssing or
separation system~, attaining a high separation
efficiency is sometimes ~ompromised by membrane
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fouling. Some processes address this problem by
stopping or reducing the flow of plasma through the
membrane, and allowing the remainder of the hlood
components to wash the upstream surface o~ tha
membrane. Other procasses address this problem by
backPlushing the ~embrane, i.e., clearing the pores
o~ the membrane by passing plasma or another fluid
back through the membrane for a relatively extended
period, for example two minutes or more.
However, these techniques app~ar to allow some
degree of fouling be~ore the membrane is cleared.
It would therefore beedesirable to provide a system
and process whereby the membrane is substantially
continually washed, or whereby fouling is prevented
or reduced to a minimum.
Disclosure of Invention
In describing the present invention, the
following terms are used as defined ~elow.
~ A3 Biological Fluid: Biological fluids
include any treated or untreated fluid associated
with li~ing organisms, particularly blood, including
whole blood, wann or cold blood, and stored or fresh
blood; treated blood, such as blood diluted with at
least one physiological solution, including but not
limited to saline, nutrient, and/or anticoagulant
solutions; blood components, such as pl~telet
concentrate (PC), platelet-rich plasma (PRP3,
platelet-poor plasma ~PPP), platelet-freR plasma,
plasma, fresh froæen plasma (FFP3, compon~nts
ob~ained ~rom plasma, packed red cells (PRC), or
buffy coat (BC); analogous blood products derived
from blood or a blood component or derived Prom bone
marrow; red cells separated from plasma and
resuspended in phy~iological fluid; and platelets
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separated from plasma and resuspended in
physiological ~luid. The biological fiuid may
include leukocytes, ox may be treated to remove,
isolate, or obtain leukocytes or other components o~
the biological fluid. As used hereill, blood product
or biological fluid refers to the co~ponents
described above, and to similar bloocl products or
biological fluids obtai~ed by other means and with
similar prop~rties.
A "unit" is the quantity of biological fluid
from a donor or derived from one unit: of whole
blood. It may also refer to the quarltity drawn
during a single donation. Typically, the volume of
a unit variesl the amount differing from patient to
patient and from donation to donation. Multiple
~mits of some blood components, particularly
pla~elets and buffy coat, may be pool~d or co~bineld,
typically by combining four or more uni~s.
B) Pla~ma-Depleted Fluid: A plasma-depleted
~luid ref~rs to a biological fluid which has had
some quantity o~ plasma-rich fluid (defined below)
removed therefrom, e.g., the platelet-rich fluid or
platelet component obtained when plasma is separated
~rom PRP, or ~he *luid which remain~ after plasma is
removed *rom whole hlood. The separation o~ ~he
plasma-rich fluid ~rom the biological fluid produces
a plasma depleted fluid havin~ an increased
concentration of platelets and/or red cells on a
volume basis. Typically, the plasma-depleted fluid
is a plateletrcontaining fluid.
C) Plasma-Rich Fluid: A plasma-rich fluid
refers to ~he plas~a portion ox plasma ~.omponent
removed ~r~ a biological fluid, e.g~, the plasma-
rich 1uid when plasma is separated ~rom P.RP, or ~he
plasma which is removed from whole blood. The
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plasma-rich f luid separated from a biol~gical ~luid
is typically cell-free and has an increased
concentrati~n of plasma on a volume basis~
Typically, the plasma-rich fluid is the plasma-
containing fluid that passes through a separationmedium. Exemplary plasma-rich fluids include
platelet-poor plasma or platelet-~ree plasma.
D) Separation medium: A separatio.n medium
refers to at least ~ne porous struct~e through
which one or more biologi~al fluids pass and which
separates one component o~ the biologic~l fluid from
another component by passing the biological fluid in
a cross flow or tangential flow manner with respect
ko the porous medium. As noted in more detail
below, the porous medium for use with a biological
fluid may be formed from any natural or synthetic
fi~er or ~rom a porous or permeable membrane (or
~rom other materials of similar sur~ace area and
pore size) compatible with a biological fluid,
typically a biological fluid containing platelets,
e.g, whole blood or PRP. The surface of the fibers
or membrane may be unmodifie~ or may ~e modified to
a~hieve a desired property.
Although the separation medium may remain
untreated, the fibers or membrane are preferably
treated to make them even more effective for
separating one component ffl a biological fluid,
e.g., plasma, ~rom other components of a biological
fluid, e.g., platelets or red cells. The separation
medium is preferably treated in order to reduce or
eliminate platelet adherence to thP medium. Any
treatment which reduces or eliminates platelet
~dhesion is included within the scope of the present
invention. Fur~hermore, the meclium may be surface
modified in order to achieve a desired critical
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wetting surface tension (CWST~ and to be less
adherent. of platelets, e.g., as disclosed in U.S.
Patent Nos. 4,880,548 and 5,100,564, and
International Publication No. W0 92/07656. Defined
in terms of CWST, a pre~erred range of CWST for a
separation medium as provided by the present
invention is above a~out 53 dynes~cm, typically
above about 70 dynes/cm. The CWST of the separation
medium may ~e dictated by its intended use.
Further, the medium may be subjected to gas plasma
treatment, an exemplary purpose for which is to
reduce platelet adhesion.
The porous medium may be pre-formed, single or
m~lti-layered, and/or may be treated to modify the
surface of the medium. If a fibrous medium is used,
the fibers may be treated either before or after
forming the fibrous lay-up. It is preferred to
modify the fiber surfaces before ~orming the ~i~rous
lay-up because a more cohesive, stronger product is
obtained after hot compression to form an integral
element.
The separation medium may be configured in any
suitable fashion~ such as a flat sheet, a composite
of two or more layexs, a coxrugated sheet, a web,
hollow fibers. A preferred separ~tion medium is
Gsnfigured as a mem~rane.
Exemplary separation media include but are not
limited to those disclosed in International
Publication Nos. W0 92/07656 and W0 93/U8904, and
30 U.S. ~akents 4,886,836; 4,906,374; 4/964~989;
4,968,533; and 5,019,260, which may include
separation media having a water pexmeability of up
o about 0.023 L/minlPa/m2 ~about 15.0
L/min/psid/ft~ .
F~ Tangential flow filtration: As used
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herein, tangential flow filtration re~ers to passing
or circulating a biological fluid in a generally
parallel or tangential manner to the surface af the
separation medium.
. _ _ _ _ .... _ _ . .. _
- The present invention provides a method for
treating biological fluid comprising passiny
biological fluid through a separation m~dium so that
a component of the biological fluid f :low5
tangentially to the separation medium and another
component flows through the porous medium, and
directing a pulsating r~verse pressure differential
through the separation medium. In a preferrad
embodiment, at least one component of the biological
~luid flows along a first fluid flow path through
khe separation medium and the pulsating reverse
pressure differential is directed opposite to the
first fluid flow path.
The present invention provides a system for
separating at least one component, e.g., plasma,
from a biological fluid comprising a separation
~edium having a fluid ~low path through the
separation medium, and a pulsating reverse pressure
di~ferential generator.
The present invention provides a system for
treating a biological fluid comprising a separation
mQdium having first and second external surfaces ancl
being suitable for passing plasma therethrough; a
housing defining firsk and second glow paths, the
separation medium being disposed within the housing
wherein the first flow path extends from the first
external surface through the separation medium to
~he second exkernal sur~ace and the second flow path
extends tangentially to the first external sur~ace
of the ~eparakion medium; and a pulsating reverse
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pressure differential generator for directing a
pulsating pressure differential against the second
external surface.
This invention also provides for a device and
method for separating platelet-poor plaslna cr
platelet-free plasma from a biological fluid, such
as PRP or from whole blood, without requiring
rotation, spinning, or centrifugatioll to ef~ect the
separation. For example, the instant invention
provides for the separation of plasma from whole
blood or PRP without centrifugationO
In a prefexred embodiment, the invention
involves the treatment of a biological fluid to non-
centri~ugally separate at least ona component fr~m
the biological fluid, e.g., treating PRP to obtain
plasma and PC, or separating plasma from whole
blood. Processes and devices provided ~y the
invention utilize a separation medium that allows
the passage of p~asma through the medium while
2 0 sub; ecting the medium to a pulsating reverse
pressure dif~ere~tial. Tangential flow of a
biological fluid parallel to the upstream surface of
the separating medium permits the passage of plas~a
through the medium, while reducing the tendency for
cellular compo~ents or platelets to adhere to the
surface of ~he medium, thus assis~ing in preventing
or reducing clogging or fouling of the separation
medium~
The device and method of the present invention
thus protect components of the biological fluid,
e~g., platelets and red blood cells, from
p~ysiological damage, and dir~ctly and effectively
minimi~e or eliminate loss or damage caused by the
currently used centrifugal separatisn processes~ by
reducing or eliminating the exposure to harmful
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centrifugation. Furthermore, the platelets and/or
red blood cells are not required to pass through yet
ano~her filtration device in order to be separated
from PRP. An advantage of the present invention may
include the increased yield of clinically and
therapeutically superior platelet concentrate and/or
platelet~free (or platelet-poor) plasma.
Advantageous features of the devices and
methods of the pre~ent invention include the
separation of at least one component o~ a biological
fluid fro~ the rest of the ~luid with minimal loss
or activation of platelets and with minimal loss of
separation medium efficiency. Further, a device as
provided by this invention can ~eliver a higher
proportion of tha platelets, particularly the
younger platelets, or plasma originally present in
the sample. The present invention Purther provides
for maximu~ recovery of plasma from whole hlood or
from PRP.
Brief Description of Drawings
Figure 1 is a schematic representation of an
embodiment of the present invention.
Figure 2 i5 a sche~atic representation of
another embodiment of the present invention.
Figure 3 is a schematic representation of
another embodiment of the present invention.
Figure 4 is schematic representation of an
exemplary device ~or generating a pulsating reverse
pressure differential.
Mod~s for Carryinq Out the Invention
The present invention involv2s the separation
af one or more components from a biological ~luid.
As provided by the present invention, a biological
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fluid, particularly blood, is exposed to a
separation medium suitable ~or passing plasma
therethrough. Clogging of the separation medium may
be minimized or prevented by treating the separation
medium to reduce platelet adhesion and/or by
directing a pulsating reverse pressure ~ifferential
through the separation medium.
Exemplary biological fluid processing systems,
which may be closed and/or sterile syste~s, are
shown in Figures 1-3. Biological fluid processi~g
system 100 may include a first contalner such as a
collection bag or syringe 19; a separation device
200 including a separation medium 16; a seconl
container ~first satellite bag) 18; and a third
container (second sat~llite bag) 17. A device for
directing a pulsating reverse prPssure differential
through the separation medium is positioned betw~en
the separation devic~ 200 and the second or third
container. In a pre~erred embodiment, the pulsating
reverse pressure differential ~enerator is a pump
400, preferably a modified peristaltic pump. The
processing system 100 may also include at least one
functional biomedical device, for example, a pump
90, and/or o~her functional biomedical devices,
including ~iltration and/or separation devices ~not
shown)O
The components of the biological fluid
processing system may be in fluid communication
through conduits. For example, as illustrated in
30 Figure 1, conduits 50A, 50B, and 50C may be used to
provide fluid communication between the components
of the sys~em. The biologiral fluid processing
system may also includ~ a seal, valve, check valve,
clamp, transf~r leg closure, stopcock, or the like
located within or on at least one of the conduits
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and!or the containers.
As illustrated in Figure 2, a separation device
as provided by the invention generally comprises a
housing 10 which includes an inlet 11 and first and
second outlets 12 and 13, respectively; a first
fluid flow path 14 between the inlat 11 and the
second.outlet 13; and a second fluid flow path 15
between ~he inlet 11 and the firs~ outlet 12. A
separation medium 16 having first and second
surfaces 16a, 16~ is positioned inside the housing
10, the separation medium being po~itioned across
the firs~ fluid flow path 14 and parallel to the
second fluid flow path 15. In this embodiment of
the invention, second container 18 may be squeezed
to yenerate a pulsating reverse pressure .
differential.
In a separation device 200, the housing 10
preferably includes ~irst and second portions lOa
and lOb, and the separation medium 16 is positioned
inside the housing 10 between the first and second
housing portions lOa, lOb. The first and second
housing portions lOa, lOb may be joined in any
convenien~ manner, for example, by ultrasonic or
heat weldi~g, an adhesive, a solv2nt, or one or more
~onnectors.
Figure 3 illustrates an exemplary system for
processing whole ~lood into each of its components.
The system includ~s a collection bag or first
container 30, second contain r 31, third container
30 32, separation devic3 33, fourth container 34, and
pumps 300 and 400. The system may also include: a
red cell barrier medium 35 and/or a leuXocyte
depletion ~ilter (not shown) between the first
container 30 and the second container 31; a
leukocyte depletion filter 36 between the first
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container 30 and the third container 32; and a
leukocyte depletion filter 37 ~etween first
container 31 and the inlet 11 of the separation
device 33.
Figure 4 illustrates an exemplary device ~or
producing a pulsating reverse pressure differential.
The exemplary device, preferably a peristaltic pump
~00, includes a housing ~01, a channel or guide 402
suitabl~ for properly positioning a conduit 403, and
a roller 404 connected to a rotor 4~5. The rotation
of the xotor 405 engages the roller 4~ with the
conduit 403, preferably at a predetermined interval
and for a predetermined period.
Each of the components of the invention will
lS now be described in ~ore detail below.
In accordance with the invention, any device or
assembly which creates a pulsating reverse pressure
differenSial is suitable for use in the invention.
Typical devices include, but are not limited to a
pump such as a peristaltic pump, a check valve, a
float valve and the like.
The number, type and location of the devices as
well as ~he manner of creating the pulsating reverse
pressure differential may be varied ac~ording to its
intended use. In one e~bodiment of the invention,
as exempli~ied in Figure 3, at least one reverse
~ressure differential creating device 400, such as a
peristaltic pump, may be located between the
separation assembly 33 and container 34, to provide
backflow across the separation med.ium. Anoth2r
embodiment of th~ invention includes a pressur~
differential generator 300, such ~s peristaltic
~ump, but ~ay not require pump 400. In this
embodiment, a reverse pressure differential through
the separation m~dium may be g~neratPd by
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restricting the flow upstream of pressure
differential generator 300 and stopping back~low
through outlet 13. For example, the system may
inciude a variable restriction flow cont:rol device
301 positioned upstream of ~he pressure dif~erential
generator 300, and a check valve 302, or the like,
positioned in the conduit communicating with outlet
13.
In a preferred embodiment, the pulsating
reverse pressure dif~erential generator provides
pulsed backflow across the separation medium in the
separation device 33 while there is continuous
transvexse or cross ~low across the separation
medium. As used hereinafter, the ter~s pulsed and
pulsating refer to any non-continuous, periodic, or
intermittent backflow across the separation medium.
For example, a typical pulsating reverse pressure
differential generator provides a reverse pressure
differential of relatively short duration, for
example, ~rom about .01 seconds to about S seconds.
In the embodiment illustrated in Figure ~,
pulsed b~ckflow may be provided by a reverse
pr~ssure di~erential creating device 400, while
transverse flow may be provided by a pressurP
di~ferential creating device 300.
Embodiments o~ the present invention may also
be configurPd in a variety of ways to expose the
separation medium 16 to back pressure or backflow to
prevent or re~uce fouling of surface 16a, while
minimi~ing hold-up volume.
With respect to the pulsating reverse pressure
dif~erential generator 400, a peri~taltic pump
providing less than a 100% duty cycle may be
u~iliz~d ~o provide for pulsed backflow. Typically,
a duty cycle of less than about 75%, more
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21 10 `.~9
preferably, less than about 50%, may be utilized.
As shown in Figure 4, a peristaltic pump 400
utilizing a single roller may be used. Multi roller
peristaltic pumps may also be used, preferably after
removing a~ least one roll~r. Thus, while devices
300 and 400 may both comprise peristaltic pumps, in
a preferred embodiment, device 300 may be a multi-
roller peristaltic pump, while device 400 may be a
single roll~r peristaltic pump as described above.
In accordance with the invention, any
~eparation device ~ay be used which clirects a
portion of a biological fluid tangent:ially or in a
crossflow manner across a separation medium, while
a~ the same time directing another portion of the
biological fluid through the separation medium.
Exemplary separation devices include ~ut are not
limited to the devices and assemblies disclosed in
International Application No. PCT/US92/09542 and
International Application No. PCT/US91/08316.
In a preferred embodiment, the separation
medium includes channels which separate the inlet
flow of biological fluid into separate ~low paths
tangential to the first sllrface l~a of the
separation medium 16 and across separation medium
16.
The plasma depleted ~luid passing tangentially
across the separation medium may be repeatedly
recirculated through the separation device.
Typically, recirculation is repeated until the
30 plasma depleted fluid in the satellite bag 31
~ontains a pre-determined ~mount or concentration of
the desired component, e.g.~ platelets.
The separation device may include an
arrangement of ribs or may comprise one or more
channels, grooves, conduits, passages, or the like
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which may be serpentine, parallel, curved, spiral,
or have a varie~y of other con~igurations ~ac~ng the
second surface 16b o~ the separation medium.
The housing and the separation medium of th~
present inventive device may be of any suitable
configuration and material. For example, the
housing, including the channels, ribs, walls, and/or
projections may be ~ormed ~rom a material that is
substantially impermeable to the biological ~luid
l~ and substantially unreactive with the biological
fluid. Alternatively, the channels m;ay be defined
by two substantially impermeable and substantially
unreactive sides and two permeable sides. For
example, in one configuration, the opposing sides of
a channel may each face a 6aparation medium,
allowing plasma-rich ~luid to flow through each
separation medium, and plasma-depleted fluid to flow
tangentially to each separation medium. In another
variation~ e.g.~ involving a half-round
configuration, at least one side of the channel is
substantially impermeable to and substantially
unr~active with the biological fluid.
While the preferred device has one inlet and
two outlets, other configurations can be employed
without adversely affecting the proper functioning
of the devica. For example, multiple inlets for a
biological fluid may be used so long as the
biological fluid flows tangentially to the ~ace of
the separation medium. Alternatively, a single
inlet ~nd a single outlet may be used. For example,
a separation device may be configured to pro~ide ~or
two liquid flow paths such that both liquid ~low
~aths comm~nicate with the inlet, but only one
liquid flow path communioates with both the inlet
and the outlet.
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The separation medium may be arranged in the
separation device in any suitable manner so long as
the biological fluid flow tangen~ial or parallel to
the separation medium is maintained to a sufficient
extent to avoid or minimize substantial platalet
and/or red cell adhesion to the separation medium.
~ne skilled in the art will recogniæe. that platelet
adh~sion may be controlled or affect~d by
manipulating any of a number o~ factors. v~locity
of the fluid flow, configuration o~ the channel,
depth and/or width of the channel, varying the depth
and/or varying the width of the channel, ~he surface
charact~ristics of the separation medium, the
smoothness of the medium's surface, and/or the ang:Le
at which the fluid flow crosses the face of the
separation medium, among other factors. Also,
platelets may not adhere as readily to a separation
m~dium having a smooth surface as compared to a
medium having a rougher sur~ace. One skilled in the
art will recognize that a desired velocity may ~e
achieved by manipulating these and other elements.
A ~eparation medium, as provided by the present
invention/ comprises a porous medium suitable for
passing a component of a biological fluid, such as a
plasma-rich ~luid, tharethrough. For example,
separation media in accordance with the invention
separate plasma from a biological fluid containing
platelets, typically whol~ blood or PRPn The
separation medium, as used herein, may include but
is not limited $o pol~meric fibers (includin~ hollow
fibers~, polymeric fiber matrices, polymeric
membranes, and solid porous media.
A separation medium according to the invention
pre~erably exhibits an average pore rating generally
or intrinsically smaller than the average size of
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platelets. For the separation of about one unit of
whole blood~ a typical separation device as provided
by the invention includes an e~fective pore size
smaller than platelets on the average, typically
S less than about 4 micrometers, preferably less than
about 2 micrometers. Preferably, platelets do not
a~lere to the surface of the separation medium, thus
reducing pore blockage. The separation medium
should also have a low af~inity or proteinaceous
components in the biological fluid, and preferably
is of sufficient size to prevent the passage of
viruses, bacteria, or the like. This enhances the
likelihood that the plasma-rich fluid, e.g.,
platelet-free plasma, will exhibit a normal
concentration of proteinaceous clotting factors,
growth factors, and other needed components. The
separation ~edium and device also enhances the
likelihood that complement activation will b~
avoided.
2~ In accordance with the invention, a separation
medium formed of fibers may be continuous, staple,
or melt-blown. The fibers may be made from any
material compatible with a biological fluid
containing platelets, and may be treated in a
variety of ways to make the medium more effective.
Also~ the fibers may be bonded, fused, or otherwise
fixed to one another, or they may simply be
mechanically entwined. A separation medium, as the
term is used herein, may refer to one or more porous
polymeric sheets, such as a woven or non-woven web
of fibers, with or without a flexible porous
substra~e, or may refer to a membrane formed, for
example, from a poly~er solution in a solvent by
precipitation of a polymer when th~ polymer solution
is contacted by a solvent in which the polymar is
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not soluble. The porous, polymeric sheet will
typically be microporous, e.g., having a
substantially uniform, continuous matrix structure
containing a myriad of small largely interconnected
pores.
A preferred separation medium of this invention
may be ~ormed, for example, from any synthetic
polymer capable of forming fibers or a membrane.
Pre~erred polymers include, but are not limited to
polyolefins, polyesters, and polyamides, e.g.,
polybutylene terephthalate (PBT) and nylon. A
polymeric membrane may also be formed from a
fluorinated polymer such as polyvinylidene
difluoride (PVDF). The most preferred separation
media are a microporous polyamide membrane or a
polycarbonate membranes.
In accordance with the invention, the
separation medium may be surface modified, typically
by radiation grafting or gas plasma treatment, in
order to achieve the desired performance
characteristics, whereby platelets are concentrated
with a minimum of medium blocking. It may a~so be
desirable to surface modify the separation medium
such that the resulting plasma solution contains
as~entia~ly all of its native proteinaceous
constituents. Exemplary membranes having a low
a~finity for proteinaceous substances are disclosecl
in U.SO Patents 4,886~836; 4,906,374; 4,964,989;
4,968,533; and S,019,260.
A typical ~eparation device as provided by the
invention includes a separation medium having an
effective surface area in the range of a~out l. 94 cm2
to about 194 cm2 (about 0.3 in2-to about 30 in~). As
used herein, the term effective surface area refers
to the surfa e area contacted by th~ biological
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fluid.
A preferable ratio of the wetted surface area
of th~ fluid ~low channel to the ~olume of the
channel ~A/V) is in the range of about 6.3 cm~ to
about 866 c~~~ (about 16 inl to about 2,200 in~).
The permeability and size of a typical
separation deYice as provided by the present
inYention is preferably sufficient to produce about
160 cc to about 240 cc of plasma at reasonable
pressures ~e.g., less than about 6.9 x 105 Pa (100
psi~, more preferably, less than about 1.38 x 105 (20
psi~ in a reasonable amount of time (e.g., less than
about one hour).
The permeability of the separation medium is
sufficient to allow the passage of a desirable
amount of a fluid therethrough at a reasonable
pressure in a reasonable amount of time. With
resp~ct to biological fluid, a preferred
permeability is in the range of from about 0.00078
L/min/Pa/m2 to about 0.023 L/min/Pa/m2 (about 0.5 to
about 15.0 L/min/psid/ft2). With respect to plasma,
a preferred per~eability is in the range of ~rom
about 0.00078 L/min/Pa/m2 to about 0.0078 L/~in/Pa/m2
~about 0~5 to about 5.0 L/min/psid/ft2), more :~
pre~erably in the range of about 0.0011 L/min/Pa/m2
to about 0.0047 L/~in/Pa/m2 (about 0.7 to about 3.0
L3min/psidlft2) 0
As provided by the present invention, all of
these typica~ para~ters may be varied to achieYe a
desi.red result, e.g., varied preferably to minimize
platelet loss, to maximize plasma-rich fluid
production, and/or to establish a certain flow ra~e.
The separation device may be positioned in the
system of the instant invention in a variety of
locAtions, as illustrated by Figures 1-3. It is
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intended that the invention is not to be limited ~y
the location or position o~ the separation device.
A system as provided by the present invention
may be used in conjunction with other functional
biomedical devices, including filtration and/or
separation devices, e.g., a device for removing
leukocytes ~rom a platelet-containing fluid or
platelet concentrate. An example of a system is
shown in Figure 3. Exemplary func~ional biomedical
devices are disclosed in U.S. Patent No. 5,100/564
and International Application Nos. :PCT/VS92/0954~
and PCT/US91/08316. A functional biomedical device,
as used herein, ref ers to any of a number of
devices, assemblies, or systems used in the
collection and/or processing of biological fluids,
such as whole blood or a blood component. Exemplary
functional biomedical devices include biological
fluid containers, such as collection or source and
satellite bags, such as first container (30),
transfer (31, 32), and storage bags (not shown);
conduits a~d connectors interposed between the
containers; clamps, closures, and ~he like; vents
and gas manipulation devices, such as air or gas
inlet or outlet devices; a debubbler; one or more
pumps (300, 400~; and a red c~ll barrier medium or
assembly r35). The functional biomedical device ~ay
also in~lude a device ~or destroying ~iological
contamina~ts, such as a high intensity light wave
chamb~rt or a device ~or sampling a biological
fluid~
The present inventiYe device may similarly be
part of an apheresis sys~e~ The biological fluid
~o be processed, the platelet-rich solution, and/or
the platele~-poor solution may be handled in either
a batch or continuous manner. The sizes, nature,
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and configuration of the present inventive device
can be adjusted to vary the capacity of the device
to suit its intended environment.
The pr~cessing of biological fluid in the
S context of the present invention may take plac2 at
any suitable time, which may be soon after donation.
For example, when the biological flu.id is donated
whole blood, it is typically processed as soon as
practicable in order to maximize the number o~
components derived and to maximi2e b:Lood component
viability and physiological activity,. Early
processing may more effectively redu~e or eliminate
conta~inating factors, including, but not limited
to, leukocytes and microaggregates.
Methods according to the invention include
passing a biological fluid through a separation
device, and subjecting the portion of the biological
fluid which passes through the separation medium to
a pulsating reverse pressure differential. For
example, the ~ethod may include directing a portion
of the biological Pluid across a separation medium,
and directing a pulsating reverse pressure
di~ferential against a downstream surface of ~he
~eparation medi~m~
Exemplary ~thods as provided by the invention
may be descri~ed in more detail by referring to
Figures 1-3.
Movement of the biological fluid through the
device and/or through the system may be effected by
maintaininq a pressure differential between a
container such as a collection bag or a syringe
containing the biological fluid, and the destination
nf the biological fluid (~.g., a container such as a
satellite bag~, to cause the fluid to ~low in a
3S desir~d direction. ~xemplary means for creating
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this pressure differential may be by gravity head,
applying pressure to the container (e.g., by hand or
with a pressure cuff)~ by placing the satellite bag
in a chamber which establishes a pressure
differential between the satellite bag and the
collection bag, e.g., a vacuum chamber or by a pump.
It is intended th~t the present in~ention is not to
be limited by the means of crPating ~he pressure
dif~erential.
In Figure 1, a unit of a biological fluid,
(e.g., donor's whole blood, or PRP) m,ay be receivad
into a first container ~9 such as a collection bag
or syringe for processiny.
With reference to Figures 1 and 2, the
biological fluid is processed by directing it from
the container 19 to separation medium 16 so that the
hiological fluid flows tangentially to the surface
of the separation mediumO Directing the biological
fluid to the separation medium may include
channelling the biological fluid tangentially t~ the
surface of the separation medium such that a plasma-
depleted ~luid passes tangentially across the
separation medium and a plasma-rich fluid passes
through the separation medium.
In Figura 2, the fluid e~ters the separation
device 200 and a portion of the biological fluid
pass s tangentially or parallel to the first surfac~e
16a of the separation medium 16 on the way to the
first outlet 12 ~ia the second fluid flow path 15.
Another portion of the biologiral fluid passes
through the separation medium 16 and is directed
toward the second outlet 13 via the first fluid flow
path 14~
As the biological fluid continues along the
3S second ~low path 1 tangentially or parallel to the
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first surface 16a of the separation medium 16, more
and more plasma-rich fluid crosses the separation
medium 16. A plasma-depleted ~luid, e.g., a
plat~let-containing fluid, then exits the housing 10
at the first outlet 1~ while plasma~rich fluid exits
the housing 10 at the second outlet 13. ~ypioally,
the plasma-rich fluid may be stored in a region
separated from the separation medium.
The plasma-rich fluid ex.iting at the second
outlet 13, and/or the plasma~deplatecl fluid exiting
at the first outlet 12, may be further processed.
For example, as shown in ~igure 2, additional
processing may includa collecting the fluids in
separate containexs, such as first satellite bag 18
and second satellite bag 17.
As sho~n in Figure 1, additional processing m;ay
include re-directing the plasma-depleted fluid to
the separation medium to deplete additional amounts
of plasma. The plasma-depleted fluid may be
repeatedly recirculated through the separation
device, e.g., until the plasma-depleted fluid
contains a pre-determined amount ar concentration of
the desired component, e.g., platelets.
In Figure 3, a biological fluid such as whole
blood is collected in girst container 30. The
biological fluid may then be separated into a
supern~tant layer and ~ sediment layer, typically by
sub3ecting the biological fluid to centrifugation.
The supernatant layer is then passed into second
container 3~, preferably making sure to pr~vent any
of the sediment layer from passing into the second
container 31, either by clamping the conduit at the
appropriate time~ or by including in the system a
red cell barrier medium.
Once the flow of ~upernatant into the second
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container 31 is halted, the sediment layer is then
passed into third container 32. A~ter the ~ransfer
of the sediment layer into third container 32 is
completed, third container 32 may b& separated from
the system and removed for further processing.
Contemporaneously with, or af~er the sediment
layer transfer, the supernatan~ lay~r present in
second container 31 i5 ~urther proce~ss~ad ~y passing
it through the separation device 33~ Pump 300 draws
the supernatant from second contain~ar 31 and
delivers it to the separation device at inlet 11. A
portion of the supernatant layer passes tangentially
to a ~eparation medium and passes out of the
separation device 33 through outlet 12. This
portion of the supernatant layer may ba recirculated
throuyh ~he ~eparati~n assambly, as shown.
Another portion of the supernatant layer passes
through ~he separation medium and passes out of the
separation device 33 through outlet 13. The
differential pressure created by pump 300 will
direct most of this fluid into ~ourth container 34,
but, in accordance with the invention, some of this
fluid will be pulsated back, preferably using pump
400, in ~he direction of the separation medium.
~5 ~s ~oted above, establishing a tangential ~low of the biological fluid being processed parallel
with or t~ngential to the face of the separation
medium minimizes platelet collaction on or in the
separatio~ ~edlum. It is believed that maintaining
a uniformly high velocity of th~ fluid across the
entire surface of the separation medium reduces or
eliminates eddies or stagnant areas of the
biological fluid develop wher~ platelets, red cells,
or other ~aterial may settle upon, stick to, and
foul the separation medium. Fluid flow channels may
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also be utilized on the side of the separation
medium opposite the biological fluid tangential flow
to control the flow rate and pressure drop of a
platelet-poor fluid, such as plasma.
In a pre~erred embodiment, passing hiological
fluid through the separation device 33 includes
providing a reverse pressure differential across the
separation medium, e.g., by creating a backflow
across the medium or against surface 16b. Without
intending to be limited to any explanation of the
mecha~ism, it is pres~ntly believed that a reverse
pressure differential may provide for minimizing
platelet adhesion to, or contact with, the
separation medium. The reverse pressure
differsntial may also.provide for minimizing
clogging of the separation medium by blood
components such as platelets and/or red cells.
The biological fluid may be supplied in any
suitable quantity consistent with the capacity of
the overall device and by any suitable means, e~g.,
in a batch operation by, for example, a blood bag
connected to an expressor or a syringe, or in a
continuous operation as part of, ~or exampl~, an
apheresis system.
In order that the inventi.on herein descri~ad
may be more fully understood, the following examples
are set out x~garding use of the present invention.
These exampl~s are ~or illustrative purposes only
and are not to be construed as limiting the present
invention in any manner.
XAMPLE 1.
WhG1~ blood was collected into an AdsolTM donor
set and was processed under ~tandard conditions to
yield a unit of PRP. The PRP was then filtered to
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rPmovP leukocytes using a filter device dascrlbed in
U.S. Patent 4,880,548. The removal efficiency was
>99 . 9~ .
The filtered PRP unit was then placed .in ~
pressure cuff to which a pressure of 300 mm Hg was
applied. The tubing exiting the bag (clamped closed
at this poi~t) was connected to the inlet port of a
separation device as shown in Fi~ures 3-6.
microporous polyamide membrane having a pore rating
of 0.65 ~icrons was used as the separation medium in
the device. The area of the membrane was about 17.4
square centimeters. The depth of the first fluid
flow path channels d~creased from about 0.03 cm near
the inlet to about 0.01 cm near the outlet. The
depth of the second fluid flow path channels was
about 0.025 cm. The width of the channels was 0.084
cm. The outlet po~ts of the device were connected
to tubing which allowed the volume of fluid exiting
the device to be measured and saved for analysis.
The test of the pres~nt invention was started
by opening the clamp and allowing PRP to enter the
de~ice. Clear fluid tplasma) was observed to exit
one port, and turbid fluid ~platelet concentrate)
exited the other port. The clear ~luid passed ~rom
the ~eparation device through a conduit to a
receiving bag. Interposed bPtween the exit port of
the separation de~ice and the receiving bag was a
peri~taltic pump which periodically pulsed a portio:n
of the clear fluid back into the separation devi~.e.
The duration of the test was 42 minutes, during
which 154 ml of plasma ~nd 32 ml of platelet
concentrate was collected~ The concentration of
~latelets in the plasma was found to b~ 1.2 x 104/~l,
while the concentration o~ platelets in the platelet
conoentration was found to be 1.43 x 105/~l~
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The above results indicate that PRP can be
concentrated to a useful level, and platelet-poor
plasma recovered, in a reasonabl~ time by a device
provided by the invention.
EXAMPLE 2.
A sample o~ 450 ml of whole blood was collected
~nder standard conditions from a human donor and
placed in a typical flexible plastic blood bag. An
analysis of the whole blood sample indicates that it
~0 contained about 203 ml plasma. A 2 cc whole blood
sample was withdrawn from the bag in a 5 cc syringe
and attached to the inlet port of a device as
provided by the invention as shown in Figure 2.
The present inventive device included a
serpentine fluid flow path with a channel length of
32.5 cm, a constant width of 0.081 cm, and a
Qnstant depth of 0.013 cm. The fluid flow path was
o~ a "C" cross-section and, on its open side,
contacted a microporous polycarbonate membrane
having a pore rating of 0.4 microns which served as
the separation medium. About 26.4 cm2 of the
microporous mem~r~ne were thereby part of the fluid
1OW path and were capable of being ~o~tacted by the
whole blood sample or processed fluid as it passed
through the device in the fluid flow path. Fluid
flowe~ ~hrough the separation medium at a ra~e of
0.2 ml/min. Satellite bag 18 was rep~atedly lightly
squeezed to induce clear fluid in the conduit to
briefly flow back into the separation medium. The
entire whole blood sample was processed in about 2
minutes. Air in the syringe was used to drive any
hold-up through the device.
At the conclusion of the processing~ a total of
about 1.6 cc of turbid fluid Sred cell containing
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fraction) and .4 cc of clear fluid was collected
from the processing of the whole blood sample. An
analysis of the clear fluid indicated that it was
plasma.
The above results indicate that plasma can be
removed from whole blood in a reasonable time
through the use of the present invention.
EXAMPLE 3.
A source bag and a satellite bag were connected
to a separation device and a peristaltic pump in a
configuration similar to that of Figure 1. The
source bag contained a unit of leukocyte depleted
PRP (approximately 200 ml). Tubing connected the
source bag to the inlet port of the separation
device, and, to provide for recirculation, tubing
connected the first cutlet port of the separation
device to the source hag. Additionally, tubing
conn~cted the second outlet port of the separation
device to the satellite bag.
A first peristaltic pump was associated with
the tubing between the source bag and the inlet port
of the separation device to provide for fluid flow.
A second peristaltic pump was associated with the
tubing between th~ outlet port of the separation
devicQ and a satellit~ bag (for recPiving plasma) to
~rovide a pulsatiny reverse prass~re differential.
The sat~llite bag was placed on a scale so that
the amount of plasma entering the bag could be
~onitored. The first peristaltic pump was activa-ted
at a flow rate of 25 cc/min and PRP was drawn fxom
the source ba~ into the device. Clear fluid
~plasma) exited the second port and entered th~
satellite bag. Turbid fluid (containing platelets3
exited the first port and was rPcirculated into the
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source bag. The source bag was periodically
squeezed to increase the mixlng of ~he platelets in
the fluid.
After approximately 35 miinutes, about 150 ml of
plasma was collected in the satellite bag and about
50 ml of platelet cbncentrate was collected in the
source bag.
The above results indicate that platelet
concentrate and platelet-poor plasma can be
r2covered in a re~sonable time, using r~circulation
of fluid by a ~evice provided by the invention.
While the invention has ~een described in some
detail by way of illustration and example, it should
be understood that the invention is susceptible to
various modifications and alternative forms, and iis
not restricted to the specific embodiments set
forth~ It should be understood that these specific
embodiments are not intended to limit the invention
but, on the contrary, the iLntention is to cover all
mo~ifications~ equivalents, and alternatives falling
within the spirit and scope of the invention.
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