Compact surface plasmon resonance-transducers with spectral readout for biosensing applications

Surface plasmon resonance (SPR) has become an important tool in sensing app lications. The most abundant set-up records surface plasmon excitation for monochromatic light as a function of the angle of incidence. This requires imaging systems and makes the overall set-up bulky. An alternative is spect rally resolved SPR, which allows to separate sensor and signal analysis. On e approach is based on the excitation of surface plasmon waves on the surfa ce of a declad optical fibre. This allows an elegant probe-type geometry, b ut is less desirable under manufacturing and liquid handling aspects. We ha ve investigated the possibility to develop compact SPR-probes combining spe ctral SPR and a planar sensor geometry. Two miniaturised set-ups were compa red to a classical optical-bench device. Performance was assessed by use of the devices as a refractometer. Results were confirmed by two bioassays: ( i) by a protein multilayer system consisting of a biotin-albumin-conjugate and polystreptavidin; and (ii) by monitoring the interaction of thrombin an d an immobilised thrombin-inhibitor. All set-ups showed good long term stab ility. Noise values from refractometry were in good agreement with bioassay s, for the classical set-up, but increased noise levels were observed for t he miniaturised set-ups indicating a requirement for improved mechanical de vice stability. (C) 1999 Elsevier Science S.A. All rights reserved.