Tumor microenvironment/NIR-responsive carbon monoxide delivery with hollow mesoporous CuS nanoparticles for MR imaging guided synergistic therapy

•A theranostic nanoplatform with copper sulfide nanoparticles carrying manganese carbonyl was synthesized.•Carbon monoxide (CO) release was simulated by endogenous hydrogen peroxide and external near-infrared laser.•Mn2+ was generated in situ in the mild acid tumor microenvironment for magnetic resonance (MR) imaging.•The nanoplatform exhibited excellent MR imaging and synergistic photothermal and CO mediated-therapy.