Paper BI+NC-ThM11
Supported Lipid Bilayers on Nanoporous Substrates for Multi-technique Membrane Sensing

Thursday, October 23, 2008, 11:20 am, Room 202

Supported lipid bilayers (SLBs) formed from the rupture of liposomes have the advantage over other planar membrane architectures in that they can be formed completely bereft of organic solvents, enabling the further incorporation of sensitive ion channels or membrane proteins.¹ Porous structures allow the use of fusogenic surfaces which enhance the formation of SLBs, while accommodating the incorporation of larger membrane proteins. By integrating these porous structures with suitable gravimetric or optical sensor surfaces that could double up as electrodes, it would be possible to conduct electrochemical measurements in tandem with, e.g., affinity measurements. For optical sensing techniques such as waveguide spectroscopy, if the pores are small enough, it would also be possible to discriminate between processes occurring on the surface and within the pores.² We have developed a process where it is possible to etch high aspect ratio pores into silicon nitride and silicon oxide with a tunable diameter between 50 nm and 150 nm using particle lithography for patterning etch masks.³ Sensor substrates for coupled plasmon waveguide resonance (CPWR) measurements, quartz crystals for quartz crystal microbalance with dissipation (QCM-D) measurements and glass slides for microscopy techniques were fabricated. The influence of nanopore density and size on the kinetics of formation of SLBs by liposome fusion was investigated by QCM-D and the structure of the lipid bilayer in the pore area was investigated by atomic force microscopy, confocal fluorescence microscopy and nanoscopy.⁴ QCM-D, microscopy and nanoscopy measurements suggest the formation of fully covering SLBs by liposome fusion on such substrates. Atomic force microscope (AFM) images and force distance measurements on individual SLBs over pores seem to indicate that the formed SLB also spans the nanopores, but are strongly deformed by the tip interaction. These results set the stage for the next phase of experiments, where electrochemical measurements can be made in situ on the waveguide or quartz crystal after the confirmed formation of a pore-spanning SLB.

¹ Reimhult, E. and Kumar, K. TIBTECH, 2008. 26(2): p. 82-89.
² Lau, K.H.A., et al. J Phys Chem B, 2004. 108(30): p. 10812-10818.
³ Reimhult, E., et al. Nanotechnology, 2007. 18(27): p. 7.
⁴ Donnert, G., et al. PNAS, 2006. 103(31): p. 11440-11445.