Engineering Anthraimidazoledione Charge-Transfer Fluorophores for Phospholipid Detection through Self-Assembly-Induced Emission

Abstract

Herein, we report the design and synthesis of anthraimidazoledione-based fluorescent probes for the selective detection of cardiolipin (CL) at pH 7.0 in PBS buffer. Compound 1, bearing a protonated tertiary amine moiety, exhibited a strong turn-on fluorescence response upon interaction with CL, with a rapid response time (<15 s) and a detection limit of 5.8 nM. The probe also demonstrated high selectivity over other mitochondrial lipids and biomolecules, with minimal background interference. Also, the sensitivity towards CL was found to be dependent on the nature of the positively charged residue at the terminal position. Mechanistic studies revealed electrostatic complexation between the cationic probe and CL, supported by a 2:1 binding stoichiometry, increased anisotropy (0.147 → 0.595), and extended fluorescence lifetime (τ = 2.78 ns). These features highlight the potential of the probe for sensitive CL quantification and diagnostic applications.