Figure 4. Schematic representation of various immobilization methods.

(A). Typical Ab structure. (B) Non-covalent immobilization of an Ab on to a solid sensor surface represented by entrapment and electrostatic interactions. (C) Covalent binding of an Ab to functionalized solid surface via amine, thiol and aldehyde groups. (D). Coupling of a biomolecule by affinity interactions with the solid surface represented by the Protein A/G and the biotin–avidin affinity-based systems.