Abstract: Ferroptosis represents a novel form of cell death distinct from other types, characterized primarily by the accumulation of lipid peroxides (LPO) in the membrane system. The development of specific probes for detecting ferroptosis-associated LPO remains challenging. The widely recognized sensor Liperfluo, for instance, is hampered by poor photostability, underscoring the need for improved molecular tools. Herein, we developed a series of novel fluorescent probes by replacing the conventional light-sensitive perylene with a stable naphthalimide core and systematically tuning the electronic properties of the triphenylphosphine (TPP) recognition head with different substituents (—OCH₃, —CF₃). The optimized probe NP-1, incorporating a trifluoromethyl group, demonstrates both superior stability under ambient conditions and specific recognition of lipid hydroperoxides, yielding a robust fluorescence enhancement of >6-fold. It was revealed that the electron-withdrawing —CF₃ group stabilizes the TPP moiety by lowering its electron density, thereby enhancing oxidative resistance. Furthermore, NP-1 enables to monitor RSL3-induced ferroptosis in live cells and the signal is specifically abolished by ferroptosis inhibitor. This work not only delivers a reliable sensor for detecting ferroptosis but, more importantly, establishes a general design principle by electronic modulation of the phosphorus center to develop stable and specific TPP-based probes for redox biology.

Key words: Reactive oxygen species, Lipid peroxidation, Triphenylphosphine, Photoinduced electron transfer