Abstract:

The uniform orientation of liquid crystal molecule can be changed easily when exposure to different biological environment and thus lead to the changes of optical images obtained from crossed polarized light with liquid crystal sandwiched between polarizer and analyzer. Based on this principle, we report the uniform planar orientation of thermotropic liquid crystals, 4-biphenyl-4′-pentyl-carbonitrile(5CB), on the films of anti-human serum albumin(anti-HSA) covalently immobilized on the surface of glass microscope slides using(3-aminopropyl)triethoxysilane(3-APTES) and glutaraldehyde(GA) and mechanically rubbed using a rubbing machine. Following immersion of these rubbed films of anti-HSA into aqueous solutions containing different concentrations of HSA, we observed the differences of images and quantificationally analyzed the relationship between gray scale of images and the concentration of HSA using the concept of weighted average of gray-scale value of image. Following immersion of these rubbed films of anti-HSA into solutions containing HSA, BSA, fibrinogen, lysozyme, we compared specific adsorption with nonspecific adsorption on these rubbed films of anti-HSA by observed the differences of images and modulation of polarized light. The result suggests that these types of substrates(rubbed films of proteins) possess high specificity. The provided methods have the potential to be useful in a variety of sensitive, label-free biomolecular detection where specific binding of a target species to its antibody(or antigen) can be imaged through analyze of the optical image of liquid crystal cell placed onto the surface.

Key words: Liquid crystal, Orientation transition, Optical detection, Human serum albumin