IgG purification by negative chromatography in amine-based ligands: A comparison of l-lysine and poly-l-lysine

Agarose gels with immobilized amine-based ligands l-lysine (Lys) and poly-l-lysine (PLL) exhibited the ability to adsorb human serum proteins and to separate immunoglobulin G (IgG) in nonretained chromatographic fractions (negative chromatography). The effect of the buffer system and pH on IgG purification on Lys-agarose and PLL-agarose showed that PLL was the most selective ligand. PLL-agarose was able to purify IgG from human serum solution diluted in Bis-Tris buffer at pH 6.0 with 79% yield and 88.7% purity (based on total protein concentration and nephelometric analysis of albumin, transferrin, and immunoglobulins A, G, and M). Human serum albumin (HSA) and IgG adsorption data showed that the first followed the Langmuir model whereas the second followed the Langmuir-Freundlich model, due to the presence of a positive cooperativity effect (n = 1.60), with the maximum adsorption capacities of 76.4 mg mL−1 for HSA and 23.6 mg mL−1 for IgG. The ΔGmax values obtained by non-linear regression of HSA and IgG adsorption data of Temkin model were similar (−7.0 kcal mol−1), indicating that the process is spontaneous in nature. The joint analysis of these data shows that PLL-agarose can be considered an alternative adsorbent for the isolation of IgG from human serum with the potential to be integrated to a purification process on a large scale.