Blood components separator disk

DESCRIPTION

<td rowspan="2">TITLE:</td><td>BLOOD COMPONENT SEPARATOR DISC</td>

<td></td>

This invention relates to methods and apparatus for use in separating fluids into components having different specific gravities. The invention finds special utility in centrifugal separation of blood components.

Centrifugal separation of blood into components with different specific gravities, such as red blood cells, white blood cells, platelets, and plasma, is known from U.S. Pat. 5, 707,331 (Wells). The apparatus shown in that patent utilizes a two-chamber recyclable processing tube, and the blood to be separated into its components is placed in one of the chambers. The processing tube is placed in a centrifuge, which submits the blood to centrifugal forces to separate the components. The supernatant is then automatically decanted in the second chamber.

To retain mainly red blood cells during decanting of the supernatant, the apparatus disclosed in Wells Patent includes a shelf placed in the first chamber at the predicted level of the interface between red blood cells and less dense components, including plasma. One problem with the arrangement represented in Wells' Patent 331, however, is that the interface varies with the particular proportions of the components (eg, the hematocrit) of the blood to be processed. Thus, if the shelf is placed at the expected interface position for the medium hematocrit blood, and the particular blood hematocrit to be processed is low, the shelf will be above the interface after separation. Such a shelf position will prevent the flow of components near the interface during settling, thereby retaining significant amounts of these components in the first chamber and reducing the separation efficiency of the system.

In US-A-5632905, a blood sample is gravimetrically separated at its lightest and heaviest stages by centrifugation in a tube. The phases are separated by a disk that has a buoyancy center and a center of mass that are spaced from each other along the axis of symmetry of the disk. The disc diameter is slightly larger than the diameter of the tube hole. 0 The disc is initially positioned in the tube with its axis of symmetry perpendicular to the tube axis, so that blood drawn into the tube can easily pass through the disc. When centrifuging, the disc will incline at an angle of 90 ° so that the axis of symmetry of the disc coincides with the axis of the tube. Once the disc has been tilted in the sample, continuous centrifugal forces will cause the disc to stretch along its axis of symmetry, thereby decreasing the disc diameter. Stretching forces exerted on the disc will temporarily decrease the effective specific gravity of the disc so that the disc remains in the upper portion of the lighter phase of the sample during the initial centrifugation portion. As centrifugation decreases, the disc plunges through the lighter phase of the sample and rests on the interface between the lighter phase and the heavier phase of the sample, thereby separating the two phases of the sample. One of the phases can then be removed from the tube without contamination of the other phase.

US-A-3972812 discloses an impregnated porous disc made of a void inert material adapted for insertion into a collection tube containing coagulated blood, which disc, after centrifugation of the tube, will allow fibrin and cellular material to be separated, from the serum by centrifugal forces during its controlled descent through the serum and will terminate when it strikes the serum-clot interface to isolate the serum from the clot.

The present invention is for an apparatus for use in separating components of different specific gravities of a fluid, comprising a container having an inner surface defining a chamber adapted to contain such a fluid to be centrifuged and a separating disc adapted for float in the fluid at an interface between these components when the fluid is centrifuged in the container, the separating disc being made of a material having a specific gravity only less than the specific gravity of the lower component, characterized in that the shape and specific gravity of the separating disc is such that it has an upper surface which, when the fluid is centrifuged in the container, meets just below the interface to allow a small layer of the lower component to form on the upper surface.

The present invention extends to a method of separating red blood plasma, comprising the steps of:

(i) supply of an appliance as set forth in the following paragraph:

(ii) introducing blood into the chamber; and (iii) chamber centrifugation.

According to the invention, a movable separating disk, which automatically positions itself at the interface between the separate components, is placed in the first chamber. In the preferred embodiment, the disc is capable of vertical movement and is designed to automatically position itself at the interface between the red blood cells and the other components in the centrifugal blood separation.

Decantation of the supernatant may be by either gravity drainage or centrifugal transfer, and a major function of the disc is to limit the flow of components below it, for example red blood cells, during decantation. This ensures that the supernatant is uncontaminated and increases process efficiency.

The invention contemplates two embodiments for the disc. In one embodiment, the disc is supported on a central axis such that a ring is formed between the perimeter of the disc and the inner surface of the first chamber. The size of the ring is such that the flow of red blood cells through it during decantation is limited such that it does not contaminate the decanted supernatant to a significant degree.

In another embodiment, the disk is arranged on the axis such that when the chamber is used for gravity settling, the disk rotates such that one end of the disk engages the chamber wall to block the flow of red blood cells.

In such an embodiment, the specific gravity of the disc and its shape may be chosen such that a major portion of the upper surface is just below the interface, thereby facilitating the release of the supernatant from the disc during decantation. This upper surface is also preferably curved to match the cylindrical shape the interface assumes during centrifugation.

1a is a longitudinal cross-section of a portion of a processing tube chamber and a separating disc not embodying the present invention;

Figure 1b is a cross section taken along line 1b-1b of Figure 1a;

Figure 2a is a longitudinal cross-section of the construction of Figures 1a and 1b, when the separating disc is inserted during settling;

Figure 2b is a cross section taken along line 2b-2b of Figure 2a;

Figure 3a is a longitudinal cross-section of another construction not incorporating the present invention;

Figure 3b is a cross section taken along line 3b-3b of Figure 3a;

Figure 4 is a longitudinal section of a processing tube chamber and a separating disc not incorporating the present invention.

Referring to Figures 1 and 2, a processing tube chamber 2, such as that shown in Wells Patent '331 has a separating disc 4 supported therein by a central axis 6. The axis 6 is designed to direct the fluid introduced into the tube. camera, to the bottom of the camera. This prevents the formation of an air bubble at the bottom of the chamber, especially when the bottom of the chamber is tapered. Thus, fluid is introduced into the chamber by inserting a cannula attached to a blood-containing syringe into axis 6 and discharging blood from the syringe to the chamber. A central opening 8 in the disc receives the axis 6 such that the disc slides easily along the axis.

axis 6 may not be necessary in all cases, for example when the bottom of the processing tube is flat. In this case, the disc does not have a center hole.

The disc is preferably made of material of specific gravity that allows the disc to float at the interface with the red blood cells. Preferably, this specific gravity is about 1.04 (eg polystyrene), which is only less than the specific gravity of red blood cells at 70% hematocrit.

Thus, when the blood is centrifuged, the disc moves to the interface between the red blood cells and the other components.

The interface will naturally assume a cylindrical shape with a cylindrical radius equal to the distance to the center of rotation of the centrifuge. The disc may be cylindrical to fit the shape of the interface.

1a, 1b, 2a and 2b, the diameters of hole 8 and shaft 6 are such that an annular spacing 10 is formed between the outer surface of the shaft and the inner surface of hole 8. Similarly, a spacing is provided. ring between the circumference of the disc and the inner surface of the tube 2.

Figures 1a and 1b illustrate the position of the disc during centrifugation, and it will be appreciated that spacings 10 and 12 are large enough to allow passage of heavier downward components, for example red blood cells and lighter upward components, for example. , plasma. However, the diameter of the central opening 8 is large enough that during decanting the disc 4 rotates as shown in the Figures. Thus, when the processing tube is rotated to the settling position, the denser red blood cells, illustrated by 14, that have accumulated under the disc, exert a force against the bottom of the disc as they attempt to flow through spacing 12. This causes the disk 4 to rotate as shown in Figures 2a and 2b until a portion of the lower outer end 16 of the disk, and also the upper outer end 18, engages the inner surface of the chamber 2. This engagement between the end 16 of the disc and the interior of the chamber ethically forms a valve that prevents the flow of red blood cells, allowing the supernatant to decant from the plasma without contamination by red blood cells. It will be appreciated that this construction requires that the transverse dimension of the disc between the ends 16 and 18 be greater than the inside diameter of the pipe such that the ends fit into the interior of the pipe when marked.

A second construct is shown in Figures 3a and 3b. According to this construction, spacing 10 is made to be small, so that the disc does not rotate appreciably during decanting, in contrast to the construction of Figures 1 and 2. It will be appreciated that an annular channel is formed by spacing 12 having This channel is an extension equal to the radial dimension of the spacing and a length equal to the thickness of the disc at the end. The flow rate of a fluid through this channel is a function of the channel dimensions, and the disc dimensions of this construction are such that the red blood cells will not appreciably flow through the 1 G channel. Preferably, the spacing extension is about from 0.005 poles to about 0.020 poles, and the length is about 0.1 poles to about 0.3 poles.

Thus, the rattan components flow through the channel during centrifugation (i.e. 1000 G), but do not appreciably flow through the channel during 1 G decantation. This allows the supernatant to be decanted without significant red cell contamination.

Figure 4 illustrates a preferred form of disc 4 which, in combination with the other parts shown in Figures 1 to 3, constitutes one embodiment of the present invention. In this embodiment, the upper surface 20 of the disc is concave, preferably cylindrical, and the disc is provided with a centered portion 22. The specific gravity of the disc material is selected such that the concave surface 20 is located just below the interface. That is, the thickness of the outer end, the length of the portion 22, and the specific gravity of the material are chosen such that the fluctuation center of the disc is just above the concave surface, and that surface is just below the interface 26. with red blood cells. This arrangement allows a small layer 24 of red blood cells to form on the upper surface.

The red blood cell layer 24 reduces the surface tension between the platelets at the interface 26 and the disk surface 20, and facilitates the release of the platelets from the disk. This is important to ensure that all platelets are decanted, and the small amount of red blood cells that can be decanted together with the supernatant does not generally represent significant contamination of the supernatant.

Modifications within the scope of the appended claims will be apparent to those skilled in the art.