Analysis of mass transport-limited binding kinetics in evanescent wave biosensors

It is shown that currently used methods for analyzing surface plasmon resonance or resonant mirror biosensor data do not adequately take into account the effects of mass transport on the kinetics of ligand association and dissociation. Conventional analyses may yield arbitrary apparent reaction rate constants lying between the mass transport rate constant and the true intrinsic chemical binding rate constants, depending on the choice of ligand concentrations used in the experiments. A new kinetic analysis of biosensor data, based upon a phenomenological two-compartment approximate description of transport, is presented and tested on experimental data and on simulated data generated with a computer model for combined mass transport and reversible binding to a single class of immobilized sites. Results of the analysis indicate the extent to which the experimental binding progress curve is transport controlled and whether or not values of chemical rate constants may be validly extracted from the data. The new analysis is independent of the details of the transport process, simple in its application, and in favorable cases permits determination of the correct values of chemical rate constants that are 10- to 100-fold greater than those that can be correctly evaluated by previous analyses.