Classical and Quantum Surface Plasmon Resonance Biosensing

Figure 8

In the Krestchmann configuration setting, three phases of contact kinetics are generated from the angle shift. In the figure, after a buffer is passed through the biosensor, a resonance dip is observed at a particular angle, and the position of this dip shifts as the analyte is pushed through the biosensor. The SPR dip shift corresponds to a change in the index of refraction on the surface of the biosensor as binding reactions occur and can be plotted as a function of time. The change in the angle-dip position can be plotted as a function of time, resulting in the sensorgram below the intensity versus angle plots. If no analyte is passed through the biosensor, then there will be no change in the dip position, and hence the baseline remains constant. The change in the signal in the angle change versus time curve is due to binding reactions that occur as the analyte is introduced to the biosensor (this can be interpreted as a change in the concentration of the dielectric above the biosensor or a change in the index of refraction of the dielectric above the biosensor, both of which cause a signal change). The concentration of the complex and the response of the biosensor are linked by the index of refraction of the analyte of the region above the gold surface, whose change is induced by the sequence of analytes passing through the flow cell: (i) buffer and ligands (association and steady state) and (ii) buffer only (dissociation). Figures were drawn from [33].