(160d) Binding of Different Analytes On Biosensor Surfaces

A fractal analysis is presented for the binding and dissociation (if required) of different analytes on different biosensor surfaces. Both, a single- and a dual-fractal analysis were used. A dual-fractal analysis was used only if the single-fractal analysis did not provide an adequate fit. This was judged using Corel Quattro Pro 8.0. A wide variety of examples available in the literature were analyzed. The systems analyzed were selected at random. The analyte-receptor systems analyzed include: (a) the binding of perfectly matched ODN (ODN-P) and non-complementary ODN during the hybridization assay with EST2-A34 reporter (Wang et al., 2007), (b) binding during the primer elongation reaction of DNA coupled directly to PAC and DNA coupled via biotin-streptavidin (Krieg et al., 2006), (c) binding and dissociation of trace amounts of trinitrotoluene (TNT) in microgram/L to anti-TNT antibody immobilized on a prototype fluorescence-based detector system (KinExA Inline Biosensor) (Bromage et al., 2007), (d) binding of EBP (estrogen binding protein) to Saccharomyces cerevisiae (Baronian and Guruzada, 2007), and the binding of different units of endonuclease activity using a molecular beacon (Ma et al,. 2007). Predictive relations are developed for the binding and dissociation rate coefficients and for the fractal dimension in the binding phase. For example, for the binding of TNT in solution to the anti-TNT antibody immobilized on a KInExA biosensor (Bromage et al., 2007) the binding rate coefficient, k for a single-fractal analysis exhibits close to a one-half (equal to 0.492) order of dependence on the fractal dimension, Df, and the dissociation rate coefficient, kd exhibits a 4.65 order of dependence on the degree of heterogenity or the fractal dimension on the sensing surface. In this case, the dissociation rate coefficient is much more sensitive to the degree of heterogeneity that exists on the sensing surface than the binding rate coefficient. The predictive relationships developed for the different analyte-receptor reactions occurring on the different biosensor surfaces are of use since they may be used to manipulate the different biosensor parameters (such as the binding and the dissociation rate coefficients) in required or desired directions. Since the biosensor systems were selected at random, the fractal analysis technique may be applied to other biosensor systems. A particular advantage of the fractal analysis method is that it provides a quantitative measure of the degree of heterogenity that exists on the biosensor surface.