Amplification of Specific Binding Events between Biological Species Using Lyotropic Liquid Crystals

This paper reports the orientational behavior of lyotropic liquid crystals (LCs) formed from 29.4 wt % potassium laurate and 6.6 wt % decanol (remainder water) that are supported on gold films possessing an anisotropic nanometer-scale topography (wavelength ∼10 nm, amplitude ∼2 nm). The gold-coated surfaces are decorated with biotin-functionalized alkanethiols to which anti-biotin immunoglobulin G (IgG) is specifically bound. Similar to the behavior of thermotropic LCs, we observe the anisotropic topography of these surfaces to cause formation of a single domain of uniform planar or near planar aligned nematic phase of lyotropic LC. However, the relaxation of the lyotropic LC to the uniform alignment is slow (∼30 min) compared to thermotropic phases (∼seconds). When the anti-biotin IgG was bound specifically to the surface functionalized with biotin, the optical appearance (using polarized light) of the lyotropic LC was azimuthally nonuniform and easily distinguished from the appearance of the lyotropic phase in the absence of bound IgG. In contrast, exposure of the surface to anti-streptavidin IgG does not perturb the uniform orientation of the lyotropic LC observed prior to exposure to the aqueous solution of IgG. These results provide new methods to align lyotropic LCs and demonstrate that lyotropic LCs are useful for amplification of specific binding events between biological species.