| Surface plasmon resonance (SPR) has been used extensively to monitor the kinetics of the adsorption of molecules at surfaces. We have quantitatively evaluated the accuracy of three different methods for measuring the kinetics of the adsorption of molecules using SPR by modeling the SPR response for an isotropic optical multilayer system. The SPR kinetic methods included the tracking of the minimum of the SPR reflected intensity and the tracking of the SPR reflected intensity at a fixed angle of incidence theta i, as well as a third novel method, the tracking of the inflection point of the SPR reflected intensity. SPR minimum tracking and SPR inflection point tracking were found to yield quantitatively accurate measures of the time constant tau of the kinetics, whereas the accuracy of the tau values determined using SPR fixed angle reflectivity tracking was found to vary significantly with the choice of fixed thetai. A method was developed to deconvolute the SPR curve shape from the SPR fixed angle reflectivity data resulting in a dramatic increase in the accuracy of the tau values.;The SPR kinetic method modeling results were validated by designing and constructing an automated angle scanning SPR imaging instrument. The instrument incorporated a novel method to remove two imaging artifacts, beam walking and image compression, that severely impact the ability to track regions of interest (ROIs) within the image as thetai is varied. By using this novel method, we are able to define multiple ROIs for an arbitrary thetai and correctly track these ROIs at all other values of thetai. In agreement with our modeling results, we show experimentally that the accuracy of the tau values obtained from the SPR fixed angle reflectivity tracking method depends significantly on the choice of fixed theta i, and that the accuracy of the tau values improves dramatically by deconvoluting the SPR curve shape from the SPR fixed angle reflectivity data. We have also used our SPR imaging instrument to study the enzymatic degradation of cellulose fibers that have been heterogeneously distributed on a gold film coated with a thin layer of thioglucose. |
