317l

Selectivity of Affinity Membranes for Immunoglobulin Capture

Cristiana Boi, Lisa Lamberti, and Giulio C. Sarti. Chemical Engineering, Mining and Environmental Technology, University of Bologna, viale Risorgimento 2, Bologna, Italy

Affinity membrane have been prepared with mimetic ligands that exhibit affinity for the Fc portion of immunoglobulins. The immobilisation of ligand was optimised with respect to time and temperature of reaction and ligand density was characterized. The affinity membranes obtained showed good stability and ligand leakage was not observed even after membrane regeneration. These new affinity membranes were experimentally characterised and tested with pure polyclonal human IgG, murine IgG, human IgM and human serum. Equilibrium and kinetic parameters have been obtained with pure protein solution, while membrane selectivity and immunoglobulins recovery were evaluated with complex mixtures. A good static binding capacity for murine IgG and human IgM was observed, with good selectivity and low non-specific binding. Results obtained with the same ligand showed that the separation behaviour depends on the membrane matrix, on the activation chemistry used for ligand coupling and on the operating conditions used for separation. Binding kinetics has a significant effect on selectivity indicating that the affinity membrane process maybe rate limited. However, this could be turned as an advantage of membranes with respect to resin chromatography, since different proteins can be isolated on the basis of different sorption kinetics and not only on the basis of different equilibrium behavior.