immunosorbent

An immunosorbent is a solid support, such as beads or a matrix, to which an antibody, antigen, or other binding ligand has been covalently attached. The immobilized ligand acts as a capture agent that binds a specific target from a mixture through antigen–antibody or receptor–ligand interactions. Immunosorbents are a key component of immunoaffinity chromatography and immunosorbent assays used in diagnostic and research settings.

Common solid supports include porous beads and matrices made from agarose, sepharose, polyacrylamide, or magnetic particles. Ligands are attached by covalent coupling to activated surfaces (for example, NHS esters or cyanogen bromide-activated resins) to create stable, reusable columns or traps. The resulting immunosorbent can selectively bind the desired molecule while allowing non-specific components to be washed away.

In use, a sample is passed over the immunosorbent so the target binds to the immobilized ligand. After washing to remove unbound material, the target is eluted under conditions that disrupt the interaction, with the aim of preserving biological activity. The column or plate can often be regenerated for subsequent use by removing bound material and re-equilibrating the binding conditions.

Applications include purification of proteins (such as antibody-based or receptor-based enrichment), removal of undesired components from complex mixtures, and diagnostic assays where immobilized ligands capture specific analytes. Limitations include finite binding capacity, potential ligand leaching, nonspecific binding, and the need to optimize elution conditions to maintain functionality.