Column-based separation of erythrocytes using aqueous polymeric two-phase systems.

Cell separation using aqueous polymeric two-phase systems is well established. For separations of cells having similar partition coefficients a multi-step counter-current distribution procedure has been used. As an alternative strategy, we have developed a column-based technique in which the dextran-rich phase of a dextran-polyethylene glycol (PEG) phase system is immobilized onto derivatized chromatography beads. The PEG-rich phase is used as the eluent. A separation of erythrocytes from different species utilizing an affinity ligand was performed. The following behaviour was observed: (i) no elution occurs below a critical affinity ligand concentration; (ii) cell recovery is proportional to affinity ligand concentration; (iii) elution volume is independent of affinity ligand concentration. The above suggest that no multi-step partitioning occurs. However, the separation achieved is considerably better than in a corresponding single-tube separation. A 1:1 mixture of dog and human erythrocytes was separated to a purity of greater than 98% using the column-based technique. The corresponding optimized single-tube separation gave a maximum purity of 84%.