2-Mercapto-5-benzimidazolesulfonic acid: an effective multimodal ligand for the separation of antibodies.

The report describes the use of 2-mercapto-5-benzimidazolesulfonic acid (MBISA) as a ligand for the separation of antibodies by chromatography. The ligand shows a relatively specific adsorption property for antibodies from very crude biologicals at pH 5.0-5.5. At this pH range most of other proteins do not interact with the resin especially when the ionic strength is similar to physiological conditions. Several characterization studies are described such as antibody adsorption in different conditions of ionic strength, pH and temperature. These properties are advantageously used to selectively capture antibodies from very crude feed stocks without dilution or addition of lyotropic salts. Demonstration was made that the adsorption mechanism is neither based on ion exchange nor on hydrophobic associations, but rather as an assembly of a variety of properties of the ligand itself. Binding capacity in the described conditions ranges between 25 and 30 mg/mL of resin. The sorbent does not co-adsorb albumin (Alb) and seems compatible with a large variety of feedstocks. Quantitative antibody desorption occurs when the pH is raised above 8.5. The final purity of the antibody depends on the nature of the feedstock, and can reach levels of purity as high as 98%. Even with very crude biological liquids such as ascites fluids, cell culture supernatants and Chon fraction II + III from human plasma fractionation where the number of protein impurities is particularly large, immunoglobumins G (IgG) were separated at high purity level in a single step.