Novel metal-chelate affinity adsorbent for purification of immunoglobulin-G from human plasma

Metal-chelating ligand and/or comonomer 2-methacrylolyamidohistidine (MAH) was synthesized by using methacryloyl chloride and l-histidine methyl ester. MAH was characterized by NMR and FTIR. Spherical beads with an average diameter of 75–125 μm were produced by suspension polymerization of methylmethacrylate (MMA) and MAH carried out in an aqueous dispersion medium. Poly(MMA-MAH) beads had a specific surface area of 37.5 m2/g. Poly(MMA-MAH) beads were characterized by water uptake studies, FTIR, SEM and elemental analysis. Elemental analysis of MAH for nitrogen was estimated as 34.7 μmol/g of polymer. Then, Cu2+ ions were chelated on the beads. Cu2+-chelated beads with a swelling ratio of 38% were used in the adsorption of human-immunoglobulin G (HIgG) from both aqueous solutions and human plasma. The maximum adsorption capacities of the Cu2+-chelated beads were found to be 12.2 mg/g at pH 6.5 in phosphate buffer and 15.7 mg/g at pH 7.0 in MOPS. Higher adsorption value was obtained from human plasma (up to 54.3 mg/g) with a purity of 90.7%. The metal-chelate affinity beads allowed one-step separation of HIgG from human plasma. The adsorption–desorption cycle was repeated 10 times using the same beads without noticeable loss in their HIgG adsorption capacity.