Amplification and transduction of biospecific interactions at surfaces by using liquid crystals

The research described in this thesis develops principles that exploit the sensitivity of liquid crystals to surfaces as a means for the detection of biologically important molecules. These principles are based on three observations: (1) the orientations of molecules forming liquid crystalline phases are highly sensitive to changes in surface structure on sub-micron length scales, (2) changes in the orientation of liquid crystals near surfaces (a few molecular lengths) can be amplified into bulk alignment transitions and (3) liquid crystals are birefringent, thus bulk alignment transitions can be transduced into readily observed optical signals.; This thesis investigates: (I) the influence of the structure of supporting gold substrates on the alignment of liquid crystals, (II) the optical response of liquid crystal to proteins bound to these substrates, (III) manipulation of the mesoscale and molecular scale structure of surfaces to control the optical response of liquid crystals to bound proteins, (IV) the generality of these methods for detection of other biologically important types of molecules, and (V) patterning of substrates with ligands and controlled delivery of analytes using microfluidic networks for multiple analyte detection. This research has made possible the development of a quantitative diagnostic assay based on liquid crystals which can rapidly detect proteins at nanomolar concentrations without the need for labeled antibodies. In addition, this work has realized methods by which the optical response of liquid crystal to bound protein can be adjusted and multiple analytes can be detected on a single, small area.