Effects of environmental parameters and composition of poly(2-hydroxyethyl methacrylate)-graft-polyamine copolymers on the retention of rat lymphocyte subpopulations (B- and T-cells)

Abstract

Retention behavior of rat lymphocyte subpopulations (B- and T-cells) was investigated on poly(2-hydroxyethyl methacrylate)-graft-polyamine (HA) copolymers with various copolymer compositions. Separation mechanism of B- and T-cells was then evaluated by focusing on several parameters, such as pH, temperature, and ionic strength. The interaction of lymphocytes with HA surfaces was mainly through the electrostatic force from their retention profile at varying ionic strengths of the medium. Temperature also has a crucial effect on the response of lymphocytes toward pH-induced phase transition of polyamine grafts at the polymer interface with aqueous milieu. At 4 degrees C, both B- and T-cells showed minimal retention on HA surfaces at pH 8. At this pH, polyamine grafts existed in a compact conformation with a low degree of protonation. However, at pHs below 8, at which polyamine grafts existed in extended conformation, the resolution of B- and T-cells was achieved. In contrast, at 23 degrees C, the phase transition of polyamine grafts significantly influenced T-cell retention, resulting in a decrease in the retention of T-cells on HA with polyamine in a compact conformation. Consequently, preferential retention of B-cells was achieved under this condition. The polyamine content was found to be another important factor affecting the retention behavior of lymphocyte subpopulations. On HA copolymers with low polyamine content (HA7, HA10), conformational transition of polyamine grafts showed a significant influence for B-cell retention, although the influence decreased with increasing polyamine content. From the study estimating the effect of neuraminidase treatment of lymphocytes on their retention to HA surfaces, sialic acid residues on the plasma membrane surface of lymphocytes are suggested as feasible anionic sites showing electrostatic interaction with polyamine grafts.