Infrared surface plasmon resonance technique for biological studies

We report on a surface plasmon resonance (SPR) technique based on Fourier-transform infrared spectrometer. In contrast to the conventional surface plasmon technique, operating at a fixed wavelength and at variable angle of incidence, our setup allows the wavelength and the angle of incidence to be varied simultaneously. We explored the potential of the SPR technique in the infrared for biological studies involving aqueous solutions. Using computer simulations, we found the optimal combination of parameters (incident angle and wavelength) for performing this task. Our experiments with physiologically important glucose concentrations in water and in human plasma verified our computer simulations. Importantly, we demonstrated that the sensitivity of the SPR technique in the infrared range is not lower and, in fact, is even higher than that for visible light. We emphasize the advantages of infrared SPR for studying glucose and other biological molecules in living cells.