Multispectral imaging of a biochip based on surface plasmon resonance and integration of chromophores

Surface plasmon resonance (SPR) technique is an optical method that allows the real time detection of small changes in the physical properties (in particular the refractive index) of a dielectric medium near a metallic surface. This technique is today applied to the realization of dynamic optical biochips where multiple interactions can be monitored in parallel and in real time. One of the main advantage compared to other techniques as fluorescence detection is that it does not require the presence of labels, which could influence the kinetics or the equilibrium of the biomolecular interactions. However, as the SPR signal amplitude depends on the refractive index shift of the dielectric medium in the contact with the metallic layer, one way to increase the SPR signal shift is to incorporate a substance possessing a strong dispersive refractive index. We present the influence of organic chromophores incorporated in the DNA target molecules on the spectral SPR response of a SPR sensor. Theoretical and experimental results are presented, showing that the DNA target molecules labeled with chromophores presenting strong spectral refractive index variation in the spectral range of the SPR spectrum induce significant spectral SPR response changes. The use of specific chromophores provides a potential way of SPR response enhancement and initial results suggest that this phenomenon can also be used in realtime SPR imaging detection.