In Situ Activatable Ratiometric NIR-II Fluorescence Nanoprobe for Quantitative Detection of H₂S in Colon Cancer

As key characteristic molecules, several H 2 S-activated probes have been explored for colon cancer studies. However, a few ratiometric fluorescence (FL) probes with NIR-II emissions have been reported for the quantitative detection of H 2 S in colon cancer in vivo . Here, we developed an in situ H 2 S-activatable ratiometric nanoprobe with two NIR-II emission signals for the detection of H 2 S and intelligently lighting up colon cancer. The nanoprobe comprised a down conversion nanoparticle (DCNP), which emitted NIR-II FL at 1550 nm on irradiation with a 980 nm laser (F 1550Em, 980Ex ). Further, human serum albumin (HSA) was combined with Ag + on the surface of DCNP to form a DCNP@HSA-Ag + nanoprobe. In the presence of H 2 S, Ag 2 S quantum dots (QDs) were formed in coated HSA, which emitted FL at approximately 1050 nm on irradiation with an 808 nm laser (F 1050Em, 808Ex ) through an H 2 S-induced chemical reaction between H 2 S and Ag +; however, the FL signal of DCNP was stable at 1550 nm (F 1550Em, 980Ex ), generating a H 2 S concentration-dependent ratiometric F 1050Em, 808Ex /F 1550Em, 980Ex signal. The NIR-II ratiometric nanoprobe was successfully used for the accurate quantitative detection of H 2 S and the detection of the precise location of colon cancer through an endogenous H 2 S-induced in situ reduction reaction to form Ag 2 S QDs. Thus, these findings provide a new strategy for the specific detection of targeted molecules and diagnosis of disease based on the in situ -activatable NIR-II ratiometric FL nanoprobe.