A Ratiometric Photoacoustic Probe with a Reversible Response to Hydrogen Sulfide and Hydroxyl Radicals for Dynamic Imaging of Liver Inflammation

Abstract Reversible imaging probes that allow for the dynamic visualization of the redox cycle between hydroxyl radical (⋅OH) and hydrogen sulfide (H 2 S) are vital to probe the redox imbalance‐involved pathological process in vivo. Herein, we report a reversible ratiometric photoacoustic (PA) imaging nanoprobe ( 1 ‐PAIN) for the real‐time imaging of ⋅OH/H 2 S redox cycle in vivo. 1 ‐PAIN displays a low PA ratio between 690 and 825 nm (PA 690 /PA 825 ), which significantly increases by ≈5‐fold upon oxidation by ⋅OH, and is switched back to the initially low PA 690 /PA 825 value upon reduction by H 2 S. 1 ‐PAIN could dynamically report on the hepatic ⋅OH production in mice during the lipopolysaccharide (LPS)‐induced liver inflammation process, and visualize hepatic H 2 S generation during the N ‐acetyl cysteine (NAC)‐induced anti‐inflammation process. 1 ‐PAIN can act as a useful tool to probe the redox state in living biology, beneficial for the study of redox imbalance‐related diseases.