Manipulation of the orientational response of liquid crystals to proteins specifically bound to covalently immobilized and mechanically sheared films of functionalized bovine serum albumin

This paper reports on the orientational behavior of thermotropic liquid crystals supported on films of biotinylated bovine serum albumin (BSA) that are covalently immobilized on the surface of glass substrates using (3-aminopropyl)triethoxysilane (APES) and disuccinimidyl suberate (DSS). The films of biotinylated BSA are mechanically sheared and then immersed into aqueous solutions of anti-biotin immunoglobulin G (IgG) prior to contact with nematic phases of 4-cyano-4'-pentylbiphenyl (5CB). Using ellipsometry, we found the capacity of the films of biotinylated BSA to bind anti-biotin IgG to be unchanged upon shearing with a polyester cloth. In contrast, we determined the orientational response of nematic phases of 5CB to the presence of bound anti-biotin IgG to be a strong function of the normal pressure applied during shearing, as well as the magnitude of the lateral displacement of the film of biotinylated BSA when in contact with the surface of the polyester cloth. The shear rate, however, appears to have little influence on the response of the liquid crystal to bound IgG. These results demonstrate that it is possible to manipulate the response (sensitivity) of liquid crystals to IgG specifically bound to sheared films of functionalized BSA by changing the manner of shearing of the films of BSA without changing the capacity of the films to bind IgG. We also report a characterization of the nanometer-scale topography of mechanically sheared films of biotinylated BSA using atomic force microscopy (AFM).