Protein contact printing for a surface plasmon resonance biosensor with on-chip referencing

Protein contact printing (pCP) has been applied to locally functionalize a novel wavelength-modulated single flow channel surface plasmon resonance (S PR) sensor with an on-chip reference. The SPR sensor has a high refractive index dielectric tantalum pentoxide (Ta2O5) overlayer covering part of the gold sensing surface to generate a SPR resonance (SPR-Ta) that is spectrall y-separated from the resonance of the Ta2O5-free Au resonance (SPR-Au). Thu s, an on-chip reference channel is provided [Electron. Lett. 35 (1999) 1105 ]. This communication demonstrates that pCP can be used for functionalizing such dual-channel SPR sensors. By using pCP bovine serum albumin (BSA) was shown to passivate the surfaces well enough to prevent non-specific protei n adsorption. In contrast, the printed 2,4-dinitrophenylated BSA (DNP-BSA) was recognized specifically by anti-dinitrophenyl antibodies (alpha -DNP) i n solution. By printing DNPBSA and BSA onto the Au and Ta2O5 surfaces, resp ectively, we demonstrate that the reversible bulk refractive index changes presented in both signals can be canceled out. Therefore, a more accurate b inding curve for the alpha -DNP/DNP interaction can be obtained by subtract ing the properly scaled SPR-Ta reference signal from the SPR-Au signal. We show that pCP is a simple, efficient, and versatile method for delivering m ultiple proteins with sufficient surface coverage and activity onto such se nsor surfaces without cross-interference to adjacent areas. (C) 2001 Elsevi er Science B.V. All rights reserved.