Method for separating cells, especially platelets, and bag assembly therefor

A method for batchwise separation of cells in a bag assembly arranged in a centrifuge rotor, said rotor comprising a central rotor compartment and an annular rotor compartment concentric to the axis of rotation of the rotor and means for reducing a volume of said annular rotor compartment during rotation of the rotor, said bag assembly comprising an essentially annular processing bag, a storage bag, and an outlet tube connecting said processing bag with said storage bag, said method comprising the steps of:

• introducing a cell suspension to be separated into said processing bag as a batch and then sealing the bag assembly;
• arranging said processing bag in said annular rotor compartment and said storage bag in said central rotor compartment;
• arranging said outlet tube in a loop extending radially outwards in the rotor from an outlet in the radially inner portion of said processing bag to a position adjacent a periphery of said rotor, and then radially inwards to said storage bag;
• separating, by centrifugation, said cell suspension in said cell processing bag into a light-weight fraction enriched on specific cells and a fraction containing cells of higher specific gravity, said fractions piled adjacent one another as annular layers, said light-weight fraction located closest to the axis of rotation of the rotor;
• transferring, upon completion of the centrifugation but while the rotor is still rotating, said light-weight fraction from said processing bag to said storage bag by activating said means for reducing the volume of said annular rotor compartment so as to expel said light-weight fraction via said outlet tube, the loop in said outlet tube acting to further separate and purify said light-weight fraction from accompanying cells of higher specific gravity.