Development of a Surface Plasmon Resonance and Plasmon-Waveguide Resonance Combined Chip for Studying the Transport Behaviors of Cell Membrane Transporters

Abstract

Surface plasmon resonance (SPR) is a powerful label-free and contact-free technique for chemical and biological sensing experiments. However, the traditional use of SPR instruments is for molecular interactions on the surface of metallic film. In order to extend the application of SPR, we integrated the concept of plasmon-waveguide resonance (PWR) and proposed the idea of PWR/SPR combined chip in order to measure the transport behaviors of cell membrane transport proteins. The PWR/SPR combined chip is composed of a silica layer with sub-micron sized pores on a thin gold film. The geometry allows us to use SPR to detect the refractive index change in the pore region, which is correlated to the target species concentration inside the pore, and PWR to simultaneously monitor the change of refractive index at the top silica surface. We deposited the giant plasma membrane vesicles (GPMV) derived from cells onto the PWR/SPR combined chip to construct the lipid membrane with native membrane proteins suspending over the sub-micron sized pores. Consequently, the detection area can be divided into two regions including the space inside the pores and the region above the grating structure. By using COMSOL simulation, we confirmed that this system allows us to simultaneously measure the change of refractive indices in the two regions across the lipid membrane. We experimentally demonstrated how the platform can be used to study the glucose transport through the corresponding membrane transport proteins (Glut 1, Glut2). In the future, we plan to use these platforms to monitor how various inhibitors or ligands could influence the transport dynamics of interested membrane transport proteins.