Dual SPR-impedance measurement system for detection of bioaffinity interactions

Abstract

The capabilities of differential impedance spectroscopy to assess bioaffinity sensors (with the surface modified with high specificity compounds) for both direct and competitive determinations were investigated using a novel Dual Surface Plasmon Resonance (SPR) - Differential Electrical Impedance (DEI) measurement set-up, aiming for development of an effective assay for detection of target analytes. The surface changes due to the specific recognition events are simultaneously monitored, on the surface of the same chip, using this custom designed system that comprises: a 3 channel SPR module, a multi-channel, differential impedance analyzer, a fully automated injection system (with capabilities for manual injecting and programmed protocols) and a 3 micro channels flow through measurement chamber. In this format, the variations of impedance of the sensor/specimen interface in response to fast specific recognition events (Ag-Ab) are revealed, while eliminating the nonspecific influences; simultaneous SPR & DEI measurements provide inner validation and expand the analyte detection range. The system was successfully tested for concentration appraise of a wide range of target analytes. Results on dual detection of low molecular analytes (gentamicin, kappa-casein) and preliminary results on whole cells will be presented. © Springer-Verlag 2007.