ABSTRACT
In principle, it is difficult for SPR sensors to clearly distinguish the signal component of target molecules from the background noise
factors associated with nonspecific absorption. First, the capture agent must have the capability for specific recognition of the target molecules. Proteins such as immunoglobulin G (IgG), which are known as immune antibodies, are frequently used as capture agents on account of their high specificity toward their target antigens (Table 3.1; Besselink et al., 2004; Yang et al., 2005). Second, the selection of capture agents with high affinity (equilibrium dissociation constant, in units of molar concentration; KD < 10-9) is necessary to achieve high sensitivity. Recently, nucleic acid aptamers and synthetic peptides have been developed as artificial antibodies with high specificity, high affinity, and ease of size control, using the molecular evolutionary systematic evolution of ligands by exponential enrichment (SELEX) process and phage display method. The obtained artificial antibodies have often been used as capture agents in SPR (Katz et al., 1995; Polonschii et al., 2010).
