Amplified fluorescence quenching and biosensor application of a poly(para-phenylene) cationic polyelectrolyte

The quenching behavior of a water-soluble cationic poly (para-phenylene) bearing quaternized ammonium side groups (P-NEt3+) was studied. P-NEt3+ is efficiently quenched by sodium anthraquinone-2,6-disulfonate (AQS) and sodium 1,4,5,8-naphthalenediimide-N,N'-bis(methylsulfonate) (NDS) in aqueous solution via a photo-induced electron-transfer mechanism. Absorption ion-pair complex indicated formation of a stable charge-transfer complex spectra of the NDS/P-NEt3+ ion-pair complex indicated formation of a stable charge-transfer complex in the ground state. A large spectral shift and band broadening occurred during AQS/P-NEt3+ complex formation, which is believed to arise due to P-NEt3+ conformational changes induced by hydrophobic interactions. Finally, a protein sensor that relies on the quenching behavior of P-NEt3+ was designed based on the quencher-tether-ligand (QTL) approach. AQS tethered to biotin (AQS-E-Biotin) was used along with P-NEt3+ to sense avidin.