We report a microfabrication approach to generate well-defined, addressable, and regenerable lipid membrane arrays in poly(dimethylsiloxane) (PDMS) microchips for label-free analysis of lipid-protein interactions with surface plasmon resonance imaging (SPRi). The multiplexed detection is demonstrated with a tethered bilayer membrane array built in parallel microchannels. These channels allow multiple measurements to be carried out simultaneously, showing low deviations for element-to-element variation in quantifiable signal. Lipid-conjugated receptors were utilized as model systems for protein binding analysis, and the feasibility of regenerating the tethering sublayer after binding was investigated. The results show that the lipid membrane can be removed effectively by nonionic surfactant Triton X-100. The small variance in SPR signal for the buildup process, i.e., <4% RSD for 3 cycles of detection, removal, and regeneration, indicates the sensing interface is highly reproducible. A calibration curve was obtained for cholera toxin using the monosialoganglioside (GM1) receptor, displaying a linear relationship in the 25 to 175 µg/mL range with a limit of detection of 260 nM. In addition, interaction of a phosphatidylinositol (PIP) with its binding protein and biotin/avidin interactions were employed for array measurements. To further enhance the SPR detection signal, a layer-by-layer amplification strategy was demonstrated that uses biotinylated antibody, NeutrAvidin and biotinylated anti-avidin, and the signal for protein binding on the membrane increased by 400%. The tethered membrane array technology, in combination with SPRi, offers an attractive platform for studies of membrane proteins, and can also find a range of applications for rapid screening of drug candidates interacting with proteins embedded in the near-native environment.
Taylor, J. D., M. J. Linman, T. Wilkop, Q. Cheng