Surface plasmon resonance (SPR) detection using the BIAcore biosensing system was employed for the detection of blood group-associated antigens (BGAA) on whole erythrocytes. The quantitative detection of erythrocytes was accomplished by covalently immobilising blood group-specific antibodies (IgM) to a dextran matrix and monitoring the cell binding response. Non-specific binding of erythrocytes to the IgM coated surface was not detected. Relatively mild regeneration conditions (20 mM NaOH) were employed to elute bound erythrocytes in order to preserve the activity of the immobilised antibody and allow the surface to be used repeatedly. Regeneration of the surface was particularly difficult when a high IgM immobilisation level was used and when the number of bound cells was high. Despite these considerations, a quantitative relationship between the cell binding response and erythrocyte concentration was confirmed. Erythrocyte preparations, diluted by a factor of ten as compared to physiological concentrations, were detectable. The occurrence of non-specific false positives appears to be minimal and allows the system to be used for blood typing. As a model study, the lectin concanavalin A (ConA) was covalently immobilised onto a hydrophilic dextran matrix and successfully used to support the capture of erythrocytes from suspension.
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