Measuring ligand–receptor binding events on polymeric surfaces with periodic wave patterns using liquid crystals

In this study, we measured ligand–receptor binding events on polymeric substrates with periodic nanostructures using liquid crystals (LCs). Periodic sinusoidal wave patterns were generated through the buckling of the poly-(dimethylsiloxane) (PDMS) substrate on a cylindrical surface followed by replicating the associated relief structures on a poly-(urethane acrylate) (PUA) surface, where a film of gold was deposited. Avidin was then covalently immobilized onto a gold surface decorated with carboxylic acid-terminated self-assembled monolayer via NHS/EDC chemistry. The optical response of the device showed that the orientation of nematic 4-cyano-4′-pentylbiphenyl (5CB) was parallel to the plane of the avidin surface. However, the formation of the avidin–biotin complexes disturbed the sinusoidal topographies of the surface, and induced a random orientation of LCs, which produced a distinctive change in the optical response. We also confirmed the specific ligand–receptor interactions using ellipsometry and atomic force microscopy (AFM). These results suggest that polymeric surfaces with continuous wavy features could be used to develop novel LC-based sensors for the detection of ligand–receptor binding events.