Methods and apparatus for isolating platelets from blood

A platelet collection device comprising

• a centrifugal spin-separator container having a cavity with a longitudinal inner surface;
• a float positioned within the cavity, the float having a base and a platelet collection surface above the base, the float having an outer surface;
• the float having a density less than the density of erythrocytes and greater than the density of plasma;
• the platelet collection surface positioned on the float at a level which places it immediately below the level of platelets after centrifugation;
• wherein a top surface of the float constitutes the platelet collection surface, and the device includes a plunger positioned above the float and substantially axially concentric with the float and the cavity, the plunger having a cylindrical outer surface which is spaced from the inner surface of the cavity;
• the bottom of the plunger defining a plasma expressing surface opposed to the platelet collection surface;
• and
• a fluid removal passageway extending through the plunger to the plasma expressing surface.

A process for separating platelets from whole blood with a centrifugal spin-separator container having a cavity with a longitudinal inner surface, a proximal end and a distal end, including a float positioned within the cavity, the float having a base and a platelet collection surface above the base, the float having an outer surface, the distance between the outer surface of the float and the inner surface of the tube being less than 0.5 mm, the float having a density less than the density of erythrocytes and greater than the density of plasma, the platelet collection surface has a position on the float which places it immediately below the level of platelets when the float is suspended in fully separated blood, the float having a channel communicating with the platelet receptor cavity for removing separated platelets after centrifugation, the process comprising the steps of

• a) introducing an amount of whole blood into the cavity, the amount of whole blood being sufficient to position the platelet collection surface immediately below the level of platelets following centrifugation at the position of the platelet collection surface,
• b) subjecting the centrifugal spin-separator container to centrifugation forces in the axial direction toward the distal end, whereby erythrocytes are caused to concentrate at the distal end, plasma to collect toward the proximal end, and platelets to collect closely adjacent the platelet collection surface, and
• c) removing platelets from the platelet collection surface through the channel wherein the float has a density greater than whole blood, and under the centrifugal forces, the float moves toward the proximal end through the sedimenting erythrocytes, releasing entrapped platelets to allow them to collect closely adjacent the platelet collection surface, whereby the amount of platelets available for removal is increased.

A process for separating platelets from whole blood with a centrifugal spin-separator container having a cavity with a longitudinal inner surface, a proximal end and a distal end, including a float positioned within the cavity, the float having a base and a platelet collection surface above the base, the float having an outer surface, the distance between the outer surface of the float and the inner surface of the tube being less than 0.5 mm, the float having a density less than the density of erythrocytes and greater than the density of plasma, the platelet collection surface having a position on the float which places it immediately below the level of platelets when the float is suspended in fully separated blood:

• wherein the device includes a plunger positioned above the float and substantially axially concentric with the float and the cavity, the plunger having a cylindrical outer surface which is spaced from the inner surface of the cavity;
• the bottom of the plunger defining a plasma expressing surface opposed to the platelet collection surface;
• and a fluid removal passageway extending through the plunger through the plasma expressing surface, wherein the process includes the steps of
• a) introducing an amount of whole blood into the cavity, the amount of whole blood being sufficient to position the level of platelets following centrifugation at the position of the platelet collection surface;
• b) subjecting the centrifugal spin-separator container to centrifugation forces in the axial direction toward the distal end, whereby blood cells are caused to concentrate at the distal end, plasma to collect toward the proximal end, and platelets to collect on the platelet collection surface;
• c) advancing the plunger in an axial direction against the top of the plasma until the plasma expressing surface is positioned near the platelet collection surface and spaced apart therefrom;
• d) extending a platelet extraction tube through the fluid removal passageway until the end thereof contacts the platelet layer;
• and
• e) removing platelet concentrate through the platelet extraction tube.

A blood platelet collection device comprising

• a flexible tube having an inner surface;
• a float positioned within the flexible tube;
• the float having an outer surface in sealing engagement with the inner surface of the flexible tube in a neutral pressure condition, the sealing engagement preventing movement of fluid between the outer surface of the float and the inner surface of the flexible tube in a neutral pressure condition;
• the outer surface of the float disengaging from contact with the inner surface of the flexible tube in an elevated pressure condition, thus enabling movement of fluid between the outer surface of the float and the inner surface of the flexible tube in the elevated pressure condition and movement of the float within the flexible tube;
• the float having a density less than the density of erythrocytes and greater than the density of plasma;
• the float having a platelet receptor cavity with a platelet collection surface positioned immediately below the level of the platelet layer in separated blood after centrifugation;
• and
• the float having a channel communicating with the platelet receptor cavity for removing separated platelets after centrifugation.

A process for separating platelets from whole blood with a flexible tube having an inner surface;

• a float having a base and a platelet collection surface above the base, the float having an outer surface, the distance between the outer surface of the float and the inner surface of the tube being less than 0.5 mm, the float having a density less than the density of erythrocytes and greater than the density of plasma, the platelet collection surface has a position on the float which places it immediately below the level of platelets when the float is suspended in fully separated blood, the float having a channel communicating with the platelet receptor cavity for removing separated platelets after centrifugation,
• the process comprising the steps of
• a) introducing an amount of whole blood into the cavity, the amount of whole blood being sufficient to position the platelet collection surface immediately below the level of platelets following centrifugation at the position of the platelet collection surface,
• b) subjecting the flexible tube to centrifugation forces in the axial direction toward the distal end, whereby erythrocytes are caused to concentrate at the distal end, plasma to collect toward the proximal end, and platelets to collect closely adjacent the platelet collection surface, and
• c) removing platelets from the platelet collection surface through the channel wherein the float has a density greater than whole blood, and under the centrifugal forces, the float moves toward the proximal end through the sedimenting erythrocytes, releasing entrapped platelets to allow them to collect closely adjacent the platelet collection surface, whereby the amount of platelets available for removal is increased.