Preparation, mechanism, and biological applications of targeting LDs ratiometric fluorescent probes for HClO detection

Hypochlorous acid (HClO) is a well-known inflammatory signaling molecule, while lipid droplets (LDs) are dynamic organelles closely related to inflammation. Using organic small-molecule fluorescence imaging technology to target LDs for precise monitoring of HClO is one of the most effective methods for diagnosing inflammation-related diseases. A thorough investigation of how probes detect biological markers and the influencing factors can aid in the design of probe molecules, the selection of high-performance tools, and the accuracy of disease detection. To this end, three fluorescent probes (TPA-B, TPA-BF and TPA-SF) based on triphenylamine (TPA) containing CN double bonds as potential reaction sites were prepared by condensing triphenylamine thiophene aldehyde (TPA-CHO) with a series of aromatic hydrazides (ArCONHNH₂). Their performance in ratiometric detecting HClO by targeting LDs had been systematically studied. The results showed that the Ar- structure in ArCONHNH₂ can not only effectively regulate the sensing performance to HClO, but also led to different oxidation products. The key reason for this was the electron cloud density around the CN bond. Furthermore, the selected probe TPA-B, which demonstrated the best spectral performance, was proficiently utilized for the detection of HClO in cells and zebrafish, as well as the detection of HClO in inflammatory diseases. This study compared the oxidation products of CN bonds by HClO and analyzed the key influencing factors. By integrating spectroscopic and imaging experiments, high-performance diagnostic agents (TPA-B) for inflammation were identified. The approach provided valuable insights into the design of multifunctional probes and opened new pathways for the diagnosis of inflammation-related diseases.