APPLICATION OF IMMUNOGLOBULIN-BINDING PROTEINS A, G, L IN THE AFFINITY CHROMATOGRAPHY

Seeking Innovative Affinity Approaches: A Performance Comparison between Magnetic Nanoparticle Agglomerates and Chromatography Resins for Antibody Recovery

Monoclonal antibodies are key molecules in medicine and pharmaceuticals. A potentially crucial drawback for faster advances in research here is their high price due to the extremely expensive antibody purification process, particularly the affinity capture step. Affinity chromatography materials have to demonstrate the high binding capacity and recovery efficiency as well as superior chemical and mechanical stability. Low-cost materials and robust, faster processes would reduce costs and enhance industrial immunoglobulin purification. Therefore, exploring the use of alternative materials is necessary. In this context, we conduct the first comparison of the performance of magnetic nanoparticles with commercially available chromatography resins and magnetic microparticles with regard to immobilizing Protein G ligands and recovering immunoglobulin G (IgG). Simultaneously, we demonstrate the suitability of bare as well as silica-coated and epoxy-functionalized magnetite nanoparticles for this purpose. All materials applied have a similar specific surface area but differ in the nature of their matrix and surface accessibility. The nanoparticles are present as micrometer agglomerates in solution. The highest Protein G density can be observed on the nanoparticles. IgG adsorbs as a multilayer on all materials investigated. However, the recovery of IgG after washing indicates a remaining monolayer, which points to the specificity of the IgG binding to the immobilized Protein G. One important finding is the impact of the ligand-binding stoichiometry (Protein G surface coverage) on IgG recovery, reusability, and the ability to withstand long-term sanitization. Differences in the materials' performances are attributed to mass transfer limitations and steric hindrance. These results demonstrate that nanoparticles represent a promising material for the economical and efficient immobilization of proteins and the affinity purification of antibodies, promoting innovation in downstream processing.

Mobile Affinity Sorbent Chromatography

The objective in routine analyses is generally to determine a small number of analytes. With samples containing ∼103 or more components there will be insufficient peak capacity to resolve analytes from nonanalytes. This issue was addressed herein through a new type of separation mechanism in which small groups of targeted analytes are bound with high affinity to a soluble analyte-sequestering transport phase (ASTP) composed of a ∼25 nm Stokes radius hydrophilic polymer core (HPC). When introduced into a 30 nm pore diameter size-exclusion chromatography (SEC) column, ASTP/analyte complexes elute within minutes, together, unretained, and relatively pure in the first chromatographic peak. Nonanalytes, in contrast, enter pore matrices of the packing material, are retarded in elution velocity, and are eluted later, separated from analytes. Fabrication of ASTPs was achieved by covalently coupling an antibody or some other affinity selector to a high molecular weight HPC. Beyond sequestering analytes, the function of ASTPs is to act as a molecular weight shifting agent, conveying an effective molecular weight to analytes that is much larger than that of nonanalytes and causing them to elute in the SEC void volume. This mode of separation is referred to as mobile affinity sorbent chromatography (MASC). Subsequent to their purification, ASTP/analyte complexes were detected by fluorescence spectrometry.

Production of pure fractions of immunoglobulin G subclass autoantibodies against tumor necrosis factor

Autoantibodies directed against cytokines are important effector molecules regulating the biological activity of cytokines. There is experimental evidence indicating that autoantibodies belonging to different immunoglobulin G (IgG) subclasses may have different functional activity. The purpose of this work was to develop a protocol for the purification of fractions of IgG subclass antibodies directed against tumor necrosis factor (TNF). We developed a series of steps, including gel filtration, positive and negative affinity chromatography, and ultrafiltration, to achieve this goal. Our protocol purified IgG subclass autoantibodies directed against TNF from a human immunoglobulin preparation. The isolation of these anti-TNF autoantibodies will enable evaluation of the effect of TNF-specific antibodies on TNF biological activity. Our newly developed technique for purifying subclasses of anti-TNF autoantibodies may be important for both basic research on the functional activity of these autoantibodies and for clinical immunology.