Ratiometric Near-Infrared Fluorescence Liposome Nanoprobe for H₂S Detection In Vivo

Accurate detection of H2S is crucial to understanding the occurrence and development of H2S-related diseases. However, the accurate and sensitive detection of H2S in vivo still faces great challenges due to the characteristics of H2S diffusion and short half-life. Herein, we report a H2S-activatable ratiometric near-infrared (NIR) fluorescence liposome nanoprobe HS-CG by the thin-film hydration method. HS-CG shows "always on" fluorescence signal at 816 nm and low fluorescence signal at 728 nm; the NIR fluorescence ratio between 728 and 816 nm (F-728/F-816) is low. Upon reaction with H2S, the fluorescence at 728 nm could be more rapidly turned on due to strong electrostatic interaction between enriched HS- and positively charged 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC) doped in the liposome nanoprobe HS-CG, resulting in a large enhancement of F-728/F-816, which allows for sensitive visualization of the tumor H2S levels in vivo. This study demonstrates that this strategy of electrostatic adsorption between HS- and positively charged molecules provides a new way to enhance the reaction rate of the probe and H2S, thus serving as an effective platform for improving the sensitivity of imaging.