Total internal reflection ellipsometry based SPR sensor for studying biomolecular interaction

Abstract

We report a label-free, highly sensitive plasmonic sensor integrated with a self-fabricated micro-fluidic flow cell, based on surface plasmon resonance (SPR) generated from the evanescent field by total internal reflection (TIR) of the incident light. Surface plasmon excitation on the sensor chip was studied with spectroscopic ellipsometry parameters ΨandΔ. Incident light was made to fall on sensor chip through Dove prism via total internal reflection, and it also helped to interact with the sample indirectly, which led to noise-free measurements. Ellipsometry parameterΔ gives the relative phase change of reflected polarized light and has a greater response to any interaction between sensor-chip and chemical/biomolecule as compared to other conventional parameters (absorbance, reflectance, etc.). Bulk refractive index sensitivity for ΨandΔ was calculated using an aqueous solution of glycerol at different concentrations (refractive indices from 1.338 to 1.364). Furthermore, we also report label-free dynamic measurements at a fixed wavelength to study specific interactions between Rabbit-IgG and Anti Rabbit-IgG proteins at a concentration of 10 µM and 300 nM, respectively. The proposed technique is self-referencing and allows us to detect the biomolecules at ultra-low concentration. Hence it could be a promising biosensing tool.