Surface Plasmon Resonance Intensity in Ex Situ Analysis of Protein Arrays Using a Wavelength Interrogation-Based Surface Plasmon Resonance Sensor

We have investigated the properties of the surface plasmon resonance (SPR) spectra obtained by scanning each spot of protein arrays using a wavelength interrogation-based SPR sensor (custom-made). The surface structure of each protein array consists of glass/metal/proteins/air (ex situ). The analysis of serial spectra showed marked increases in SPR intensity and wavelength at the boundary area of protein array spots, which were mainly caused by the background signal from the glass substrate. However, at the central area, protein interaction caused an increase in SPR wavelength, and a decrease in SPR intensity. There was no significant difference between the central and boundary areas in terms of the roughness and thickness of the gold film. These results suggest that SPR intensity is a good indicator for distinguishing psuedosignals from real signals of biospecific interactions in the analysis of protein arrays using wavelength interrogation-based SPR sensors.