SPR biosensors: simultaneously removing thermal and bulk-composition effects

Surface plasmon resonance (SPR) is an established method for sensing analyt es by monitoring changes in the plasmon dispersion relation (PDR) at the in ter-face of a thin metal film and a fluid. When SPR is used in sensors for specific analytes, the changes in the plasmon dispersion relation of intere st are generated by the binding of analytes to receptors immobilized to the metal film. However, changes in the PDR can also be generated by changes i n the index of refraction of the bulk solution containing the analytes via changes in composition or temperature. Thus, there exist inherent systemati c errors in SPR based chemical sensing when temperature and/or concentratio n conditions are not carefully controlled. We have demonstrated the efficac y of a single, simple, and inexpensive method for simultaneously discrimina ting both effects from those of binding and/or debinding of analytes with a two-element SPR sensor array. Although two-element SPR arrays have been us ed before, their ability to simultaneously discriminate out both thermal an d bulk-composition (TAB) effects (in both SPR spectroscopic and spectrophot ometric schemes) has not been previously addressed. We show an example of a relatively inexpensive SPR biosensor instrument using a compensator elemen t and its stability over a period of days. This demonstration has implicati ons for the development of reliable SPR based chemical sensors for environm ental and remote sensing applications. (C) 1999 Published by Elsevier Scien ce S.A. All rights reserved.