- 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.