Surface-plasmon resonance with infrared excitation: Studies of phospholipid membrane growth

Abstract

We report on a surface-plasmon resonance (SPR) technique based on a Fourier transform infrared spectrometer for biological and surface-sensitive applications. In contrast with conventional surface-plasmon techniques, which operate at a fixed wavelength and a variable angle of incidence, our setup allows independent variation of the wavelength and the angle of incidence. By the proper choice of these parameters, we achieve optimal coupling to the surface plasmon and high sensitivity. Moreover, by using infrared rather than visible light, we achieve an extremely narrow angular-dependent surface-plasmon resonance. This results in a very sensitive SPR technique that can easily sense one molecular layer. We take advantage of the extremely narrow SPR in the infrared range and use it to study the growth dynamics of the phospholipid layer, which is the main constituent of the biological cell membrane. In particular, we distinguish the difference in the growth dynamics of this artificial membrane from a solution under different conditions of liquid flow (continuous flow or injection).