DIRECT COLORIMETRIC DETECTION OF A RECEPTOR-LIGAND INTERACTION BY A POLYMERIZED BILAYER ASSEMBLY

Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct c olorimetric detection method based on a polydiacetylene bilayer assemb led on glass microscope slides has been developed. The bilayer is comp osed of a self-assembled monolayer of octadecylsilane and a Langmuir-B lodgett monolayer of polydiacetylene. The polydiacetylene layer is fun ctionalized with an analog of sialic acid, the receptor-specific ligan d for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbon e signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direc t colorimetric detection by polydiacetylene films offers new possibili ties for diagnostic applications and screening for new drug candidates or binding ligands.