Piezoelectric Crystal Impedance Analysis for Investigating the Changes of Interfacial Properties due to Interaction of Cobalt Salt with DNA Immobilized on Biosensor

Abstract

The interaction of a cobalt compound, tris(2,2′-bipyridyl)cobalt(III) perchlorate (Co(bpy)3(ClO4)3·3H2O), with DNA immobilized on a biosensor has been investigated by using a piezoelectric impedance technique. The changes of equivalent circuit parameters were used to characterize the changes of the interfacial properties of the piezoelectric biosensor in the reaction system. It was found that the interaction of cobalt compound with double-strained DNA (dsDNA) could be described by a sum of two exponential functions, suggesting two corresponding kinetic steps. As for dsDNA, the change of static capacitance showed a linear correlation with time. Comparative experiments indicated that dsDNA with double-helical structure is more easily bound with cobalt compound than single-strained DNA (ssDNA). From the frequency curve, some parameters related to this interaction, such as cross-linking ratio, binding ratio, and the maximum initial rate were roughly estimated to be 2%, 1.15, 0.72 Hz/s (or 0.12 Hz/s for ssDNA), respectively. The linear relationship between the frequency change and the motional resistance was verified to reflect the changes of the density-viscosity in the biological reaction.