Charge-driven complexes formed by conjugated polyelectrolytes as sensing platforms for biogenic amines

We developed sensing platforms to detect and differentiate various types of biogenic amines, cadaverine, putrescine, spermine, histamine, tyramine and tryptamine by monitoring the changes in fluorescence signal. The sensing platforms comprised a carboxylated polyfluorene derivative doped with benzothiadiazole acceptor moieties in a small fraction (20%). When utilized as an individual sensing component, the conjugated polyelectrolyte detects all BAs nonselectively via binding-induced fluorescence quenching. If the conjugated polyelectrolyte forms an intermediary charge-driven complex with an oppositely charged surfactant, a Fo center dot rster resonance energy transfer (FRET) response is triggered. Biogenic amines are detected through their effects on the FRET signal as enhancement, reduction, or no effect. We formed intermediary charge-driven complexes at nonstoichiometric, cation deficient and excess conditions. Supramolecular interactions governed the co-assembly and disassembly caused by the targeted amines on the conjugated polyelectrolyte-surfactant complex. Therefore, structural and charge-related differences enabled their selective detection in our sensing platforms. Among them, spermine exhibited the highest FRET enhancement effect due to its polycationic aliphatic structure by engaging in multi-point interchain contacts among conjugated polyelectrolyte chains. In contrast, tryptamine showed a unique quenching effect on the FRET signal due to the steric hindrance created by its bulky, heterocyclic structure, leading to the dissociation of the complexes.