New conjugated poly(pyridinium salt) derivative: AIE characteristics, the interaction with DNA and selective fluorescence enhancement induced by dsDNA

Abstract

Herein, a new conjugated poly(pyridinium salt) derivative L was synthesized by ring-transmutation polymerization reaction for the purpose of sensitive and selective fluorescence sensing of DNA. Cationic L exhibits aggregation-induced emission (AIE) characteristics that is weakly emissive in solution but highly luminescent in the aggregate state. Based on its AIE activity, a fluorescence turn-on biosensor for calf thymus DNA (ctDNA) detection is developed, which shows excellent selectivity with a detection limit down to the 10⁻⁸ M⁻¹ in CH₃CN–phosphate buffer solution (PBS) (2 mM, pH 7.4) (v/v 1 : 1). Further, the interactions between L and ctDNA are carefully investigated by UV-vis absorption spectra, dynamic light scattering (DLS) measurements, thermal denaturation studies, circular dichroism (CD) measurements, as well as competing experiments with ethidium bromide (EB). More interestingly, L exhibits selective fluorescence enhancement induced by double-stranded DNA (dsDNA), therefore, L was also successfully utilized as fluorescent probe to follow the ctDNA cleavage process by bovine pancreatic deoxyribonuclease I (DNase I).