A kinetic study of analyte-receptor binding and dissociation for surface plasmon resonance biosensor applications

A fractal analysis which takes into account the effect of surface heterogeneity brought about by ligand immobilization on the reaction kinetics is presented. The binding and dissociation of estrogen receptors ERα and ERβ to different ligands is analyzed within the fractal framework. The heterogeneity on the biosensor surface is made quantitative by using a single number, the fractal dimension, D_f. The analysis provides physical insights into the binding of these receptors to different ligands and compounds, particularly the EDCs (endocrine disrupting compounds), which can have deleterious affects on humans and wildlife. Single- and dual-fractal models were employed to fit the ER binding data obtained from literature. Values of the binding and dissociation rate coefficient and fractal dimensions were obtained from a regression analysis provided by Corel Quattro Pro 8.0 (1997). In some cases both a single- and dual-fractal model was required to completely and adequately describe the kinetics involved. Values for the affinity, K_D (=k_d/k_a) were also calculated. This provides us with some extra flexibility in designing biomolecular assays.