A dual-modality fluorescent probe for peroxynitrite based on TICT-AIE synergy: Environmental responsiveness and biological imaging

Peroxynitrite (ONOO⁻) is a highly reactive nitrogen species implicated in diverse physiological and pathological processes, yet its transient nature poses significant challenges for real-time monitoring. Herein, we report a novel environment-adaptive fluorescent probe, TBN-BPE, that exhibits dual-mode fluorescence response to ONOO⁻ based on the interplay between twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) mechanisms. Structurally, TBN-BPE integrates a triphenylamine donor, a benzothiazole acceptor, and a boronate ester recognition unit, enabling selective cyclization upon ONOO⁻ exposure. In DMSO-rich media, ONOO⁻ treatment induces a “turn-on” fluorescence response via TICT suppression and enhanced radiative decay. In contrast, under water-rich conditions, ONOO⁻ promotes aggregation and π–π stacking, resulting in fluorescence quenching and a hypsochromic shift. The probe exhibits high selectivity for ONOO⁻ over competing reactive species, with detection limits of 71 nM and 77 nM under water-poor and water-rich conditions, respectively. Practical utility is demonstrated through quantitative detection in spiked human saliva samples and dual-channel fluorescence imaging of exogenous and endogenous ONOO⁻ in A549 cells. This work introduces a versatile probe design strategy for responsive and context-aware imaging of reactive nitrogen species in complex biological environments.