A novel Cys-activated NIR-II fluorescent probe for rheumatoid arthritis fluorescence imaging in vivo†

Rheumatoid arthritis (RA) is a common inflammatory disease that greatly restricts normal joint movement. The excessive production of Cys (Cysteine) is one of the biomarkers of rheumatoid arthritis. However, research on relevant fluorescent probes mainly focused on the NIR-I region, with few developments of fluorescent probes in the NIR-II region. Therefore, in this study, we designed and synthesized a NIR-II fluorescent (NIR-II FL) probe, GY-G, for specific detection of endogenous Cys in RA with excellent NIR-II FL imaging performance. This probe exhibited a NIR-II FL emission exceeding 920 nm and a large Stokes shift of 110 nm. Additionally, GY-G responded to Cys with high sensitivity and selectivity in an RA model. Notably, we successfully achieved NIR-II FL imaging of endogenous Cys in an RA model by using GY-G. Significantly, GY-G is expected to be a potential candidate for early diagnosis of RA. A NIR-II fluorescent probe for detecting endogenous Cys in arthritis models was developed for the first time. Overall, this probe has great potential in exploring the pathophysiological processes of Cys-associated arthritis with a range of biomedical tools that can be used for NIR-II fluorescence imaging.