Ratiometric nitric oxide fluorescent probe in the second near infrared window for the visualization of inflammation

Nitric oxide (NO), a key inflammatory mediator, plays dual roles in both immune response and inflammatory progression. Real-time, dynamic monitoring of NO levels in vivo is therefore essential for elucidating related pathological pathways. To address this challenge, we developed a ratiometric fluorescent probe, CSQD@PIB, with emission in near-infrared-II window (NIR-II) for the visualization of NO in inflammation models. This probe integrates two luminescent components: lead sulfide core-shell quantum dots (CSQD) emitting in the 1500-1700 nm band as an invariant internal reference for spatial localization and a NO-responsive conjugated polymer (PIB) exhibiting specific fluorescence enhancement in the 1000-1300 nm band as a quantitative sensing unit. By correlating the intensity ratio of the two emission channels, the probe enables simultaneous, real-time visualization and quantification of NO in the inflammatory site. Experiments demonstrate that CSQD@PIB can monitor the dynamics of NO generation in various pathophysiological processes in vivo, providing a reliable, self-calibrating imaging tool with high signal-to-noise ratio for NO-related studies in living mammals.