Differential Affinity of Lymphocyte Subpopulations toward PHEMA Surface Derivatized with a Small Amount of Amino Groups—Evaluation under the Regulated Shear Stress

Abstract

The interaction of rat lymphocyte subpopulations with the surface of poly[ N-methyl- N-(4-vinylphenethyl)ethylenediamine- co-2-hydroxyethyl methacrylate] (HAV copolymer) was evaluated under controlled shear stress by using a flat ribbon-like chamber with a plane-parallel type channel equipped with a polymer-coated bottom wall (hybrid field-flow fractionation/adsorption chromatography (FFF/AC) technique). Due to this simple geometry, it was able to control the hydrodynamic shear stress at the channel wall resulting from the parabolic flow in the channel. The cells in the channel were able to be detached from the polymer surface by increasing shear stress to exceed the strength of cell/materials interaction. Judging from the value of critical shear stress for lymphocyte take-off, the interaction force of lymph node lymphocytes was concluded to be minimized on the HAV copolymer containing 3 mol% of N-methyl- N-(4-vinylphenethyl)ethylenediamine (HAV3). This anomalous minimum of lymphocyte attachment by the introduction of a small amount of cationic sites on the surface is considered to be due to the drastic increase in free water content of polymers triggered by incorporated amino groups, which was demonstrated through DSC measurement. Further, by varying the settling time of lymphocytes in the chamber as well as by changing shear stress through the different profiles of applied flow, differential take-off of two major subpopulations of lymphocytes, B cells and T cells, was achieved on the HAV3 surface due to the differential contribution of the electrostatic interaction with HAV3 between B cells and T cells. This result indicated that the separation of B cells from T cells can be done by FFF/AC technique with a HAV3-coated chamber.