Comparison of reflectometric interference spectroscopy with other instruments for label-free optical detection.

On the basis of kinetic measurements of biomolecular interactions, a reflectometric interference spectroscopy (RIfS) setup is compared with two commercial instruments. These instruments are based on evanescent wave techniques, surface plasmon resonance (SPR) (represented by BIAcore 2000) and resonant mirror (RM) technique (using IAsys plus). All methods allow a label-free and time-resolved optical detection of biomolecular interaction. These methods are mainly used in biomolecular interaction analysis (BIA). They provide practical techniques for quantifying equilibrium constants and rate constants over several orders of magnitude. The general parameters of the three detectors, namely baseline noise and drift as well as overall sensitivity and limits of detection were compared. The fluid handling and the related implications on the measurements have also been considered. The interaction between thrombine and thrombine inhibitor (TI) was investigated as a test system with the three different methods and the kinetic rate constants were determined and compared. For this TI was immobilized on the surface and binding of thrombine was monitored time-resolved. Determination of the kinetic rate constants could prove that the RIfS set-up is comparable with SPR using BIAcore 2000 and RM technique represented by IAsys plus.