Activatable Nanoprobes for Dual-Modal NIR-II Photoacoustic and Fluorescence Imaging of Hydrogen Sulfide in Colon Cancer

High hydrogen sulfide (H2S) expression has been shown to play a crucial role in tumor growth and proliferation in colon cancer. So far, most probes used for monitoring H2S offer single-modal imaging, which makes the collection of accurate information for tumor diagnosis difficult. In the present study, a novel dual-modal imaging probe in the second near-infrared (NIR-II, 950-1700) window is proposed and constructed by coating a uniform shell of polydopamine (PDA) on the surface of cuprous oxide (Cu2O)-conjugated downconversion nanoparticles (DCNPs). Of note, DCNP-Cu2O@PDA is in the "on" state, with emission centered at 1550 nm (irradiation using a 980nm laser) in non-neoplastic tissues. Colon tumors with endogenous H2S overexpression can induce the in situ transformation of Cu2O to copper sulfide (Cu2-XS?. Owing to the competitive absorption between Cu2-XS and DCNPs at a wavelength of 980 nm, the generated DCNP-Cu2-XS@PDA exhibits a quenched NIR-II fluorescence (FL) signal. Meanwhile, Cu2-XS exhibits a strong absorbance at 1250 nm, enhancing the NIR-II photoacoustic (PA) signal accompanied by NIR-II FL attenuation. The switching in PA and FL signals at the tumor site offered "double assurances" for the accurate monitoring of H2S. A novel dual-modal imagingprobe in the second near-infrared (NIR-II) window is developed with "double assurances" for the accurate imaging and monitoring of H2S in vivo.image