- Abstract Supramolecular assemblies constructed from polymerized polydiacetylene (PDA) lipids have been shown to exhibit colorimetric transitions, which are induced by a variety of biological analytes. Among the analytes that give rise to the unique blue-red color changes in the system are viruses, toxins, antibacterial peptides, ions, and antibodies. The colorimetric transitions occurring in the PDA-based aggregates are associated with structural perturbations within the conjugated backbone of the polymer. The rapid and specific color changes observed in the PDA systems open wide-range possibilities for biosensor, drug discovery, and diagnostic applications. Drug Dev. Res. 50: 497–501, 2000.© 2000 Wiley-Liss, Inc.