This review highlights the design strategies of typical organic fluorescent probes for reactive carbonyl species and their application in biological imaging.

Chemical warfare agents (CWAs) such as phosgene and nerve agents pose serious threats to our lives and public security, but no tools can simultaneously screen multiple CWAs in seconds. Here, we rationally designed a robust sensing platform based on 8-cyclohexanyldiamino-BODIPY (BODIPY-DCH) to monitor diverse CWAs in different emission channels. Trans-cyclohexanyldiamine as the reactive site provides optimal geometry and high reactivity, allowing trans-BODIPY-DCH to detect CWAs with a quick response and high sensitivity, while cis-BODIPY-DCH has much weaker reactivity to CWAs due to intramolecular H-bonding. Upon reaction with phosgene, trans-BODIPY-DCH was rapidly converted to imidazolone BODIPY (<3 s), triggering green fluorescence with good sensitivity (LOD = 0.52 nM). trans-BODIPY-DCH coupled with nerve agent mimics, affording a blue fluorescent 8-amino-BODIPY tautomer. Furthermore, a portable test kit using trans-BODIPY-DCH displayed an instant response and low detection limits for multiple CWAs. This platform enables rapid and highly sensitive visual screening of various CWAs.

Compared to normal cells, cancer cells require more energy supply during proliferation and metabolism. In living cells, in addition to mitochondria, lipid droplets are also an important organelle for providing energy. Studies have shown that the number and distribution of lipid droplets change significantly during the production of lesions in cells. At this stage, the predisposing factors for the development of cellular lesions are not clear, thus leading to limitations in the early diagnosis and treatment of diseases such as liver injury, fatty liver, and hepatitis. To meet the urgent challenge, we used a near-infrared emission fluorescent probe SSR-LDs based on the intramolecular charge transfer effect (ICT) to detect polarity changes within intracellular lipid droplets. The probe SSR-LDs has ultra-sensitive polarity sensitivity, excellent chemical stability and photo-stability. In addition, by comparing normal and cancer cells through cell imaging experiments, we found that the robust probe has the ability to sensitively monitor the changes in lipid droplet polarity in the living cells. More importantly, using the constructed fluorescent probe, we have achieved an in vitro fluorescence detection of liver injury and fatty liver, and the detection of hepatitis at the in vivo level. The unique fluorescent probe SSR-LDs is expected to serve as a powerful tool for the medical diagnosis of diseases related to lipid droplet polarity.