Real-time, label-free monitoring offers a wide range of applications to the biotech field. We developed an integrated bio-sensing platform which adapts a circular polarization interferometry configuration and a phase modulated ellipsometer to improve the performance of biomolecular measurements. An bithiophene-based conductive linker-5′-(mercapto)-[2, 2′-bithiophene]-5-carboxylic acid was developed for detecting antibody–antigen interactions. In this study, the biomarker interferon-gamma (IFN-γ), one of the most important indicators of tuberculosis, was chosen to test and verify the sensitivity of our measurement system. Our experimental results showed that an increase in the concentration of the IFN-γ (64 pM to 1 μM) was usually accompanied by a phase increase. This result is good evidence that our biosensing system can be useful for analyzing biomolecular interactions.