Polydiacetylene (PDA)-based colorimetric detection of biotin-streptavidin interactions

The natural binding of streptavidin (STA) for a small molecule, biotin, has made it a useful tool in specific targeting application, due to their most specific noncovalent biological interactions in nature. Here, we describe a polydiacetylene (PDA)-based colorimetric biosensor to detect the STA-biotin interactions. We synthesized two kinds of biotin-labeled 10,12-pentacosadiynoic acid (PCDA) monomers having 2(ethylene oxide) or 3(ethylene oxide) spacer and prepared biotin-modified PDA liposomes using them. Upon the addition of STA, the modified PDA liposomes showed a color change from blue to red in about 1h followed by their aggregation and precipitation. The aggregation was found to be due to the cross-linking between the PDA liposomes caused by the STA having four biotin binding sites, which was confirmed by their TEM analysis. Since the STA-biotin interactions are widely adopted for various biological detection systems; the biotin-modified PDA sensor developed in this study has enormous potentials for the development of various colorimetric biosensors.