AIE-ESIPT synergistic fluorescence probe for superoxide and hypochlorite using acetoxy-substituted tetraphenyl imidazole

Abstract

Background: Reactive oxygen species (ROS) are highly reactive molecules that play pivotal roles in various cellular functions such as signaling, immune responses, and metabolic regulation. While they are essential in normal physiological processes, excessive ROS accumulation leads to oxidative stress, which damages cellular structures, including lipids, proteins, and DNA, contributing to diseases like cancer, neurodegeneration, and cardiovascular disorders. Therefore, the development of effective detection strategy for the selective detection of ROS, particularly superoxide (O₂^•-) and hypochlorite (ClO^-), is crucial for understanding their roles in cellular processes.

Results: In this study, we introduce an acetoxy-substituted tetraphenyl imidazole (AcOPI) as a fluorescence probe specifically designed to detect superoxide (O₂^•-) and hypochlorite (ClO^-) through a unique combination of aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT). The probe demonstrates a remarkable 96-fold fluorescence enhancement upon ROS exposure, with a large Stokes shift (Δλ = 145 nm) that minimizes interference from background fluorescence. Additionally, AcOPI exhibits low self-quenching and high aqueous compatibility, which are advantageous features for its application in biological systems. These properties make AcOPI a highly sensitive and selective tool for ROS detection in aqueous environments. These results could be applied to follow-up research focused on developing fluorescence probes that absorb and emit detectable visible light for spatiotemporal and real-time detection in living systems.

Significance: The successful development of AcOPI as a fluorescent probe for detecting superoxide and hypochlorite offers a promising strategy for monitoring ROS under both physiological and environmental conditions. Owing to its high sensitivity, large Stokes shift, and excellent aqueous compatibility, AcOPI enables real-time ROS imaging and detection, underscoring its potential for diagnostic applications in ROS-related diseases. This study further suggests a potential application in elucidating the link between chronic inflammation and cancer by exploring the mechanisms of ROS interactions during disease progression. Applying our methodology to chronic inflammation models may help clarify the integrated ROS signaling pathways involved in tumor development. Beyond its medical relevance, AcOPI also shows strong potential for environmental monitoring of aquatic organisms subjected to oxidative stress induced by pollutants such as heavy metals, pesticides, and disinfectants. Although AcOPI demonstrated promising performance in aqueous systems, several challenges remain for in vivo applications. The limited tissue penetration of visible light may restrict the use of these probes for deep-tissue imaging or targeted delivery.

Keywords: Acetoxy-substituted tetraphenyl imidazole (AcOPI); Aggregation-induced emission (AIE); Excited-state intramolecular proton transfer (ESIPT); Reactive oxygen species (ROS).