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 (SPR) 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 spectrally-separated from the resonance of the Ta2O5-free Au resonance (SPR-Au). Thus, 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 protein adsorption. In contrast, the printed 2,4-dinitrophenylated BSA (DNP-BSA) was recognized specifically by anti-dinitrophenyl antibodies (α-DNP) in solution. By printing DNP-BSA and BSA onto the Au and Ta2O5 surfaces, respectively, we demonstrate that the reversible bulk refractive index changes presented in both signals can be canceled out. Therefore, a more accurate binding curve for the α-DNP/DNP interaction can be obtained by subtracting 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 multiple proteins with sufficient surface coverage and activity onto such sensor surfaces without cross-interference to adjacent areas.