Cation-selective color sensors composed of ionophore-phospholipid-polydiacetylene mixed vesicles

Supramolecular assemblies of vesicles composed of ionophores and phospholip ids embedded in a matrix of polymerized diacetylene [PDA] lipids are shown to undergo visible color changes in the presence of ions in solution. The b lue-to-red color transitions of the vesicles are directly related to bindin g of the cations to the ionophores, and their association with the lipids. The system detects cations in submillimolar concentrations and demonstrates a significant ionic selectivity, in particular between the physiologically important ions Na+ and K+.