Surface plasmon resonance ellipsometry based sensor for studying biomolecular interaction.

A simple surface plasmon resonance (SPR) ellipsometry equipped with a dove prism and micro-fluidic flow cell is adopted to investigate and study basic properties of biomolecular interaction. Using a dove prism greatly simplifies the optical alignment and the use of micro-fluidic cell helps reduce significantly the volume of the biological sample required in the experiment. By recording the ellipsometry data in terms of relative changes in the ellipsometric parameters, Psi and Delta as sensor signals we can understand the biomolecular interaction. Spectroscopic measurements were performed to check the bulk sensitivity, which further helps determine the corresponding wavelength for maximum sensitivity. Furthermore, dynamic measurements at a fixed wavelength were also done and allow the observation of real-time response to the changes in surface properties on a metallic film. Such a simple technique gives an index resolution around 1.64x10(-6) which is better than the conventional SPR method based on the resonance angular detection. This technique yields sensitivity sufficient enough to detect changes in the effective thickness of biomolecular layer. Biological processes such as adsorption of protein to metal and protein-protein interaction can be understood from the optical response of the sample surface. Such technique is a promising candidate in developing profitable and user-friendly biosensors. Furthermore, this kind of characterization technique is non-destructive, label free, and sensitive with a sub-nanometer resolution in thickness.