Oxygen‐Deficient Bimetallic Oxide FeWO X Nanosheets as Peroxidase‐Like Nanozyme for Sensing Cancer via Photoacoustic Imaging

Nanozymes with high catalytic activity and great stability have attracted increasing interests as the promising alternative to natural enzymes for applications in various fields. In this study, a new type of highly efficient peroxidase‐like nanozymes based on FeWO X nanosheets (NSs) synthesized by a thermal‐decomposition method is reported. Owing to the sheet‐structure with maximized utilization of catalytic sites (Fe atoms and oxygen vacancies), such FeWO X NSs exert efficient enzyme activity to trigger catalytic decomposition of hydrogen peroxide (H 2 O 2 ) into hydroxyl radicals (•OH). A nanozyme‐based ratio‐metric nanoprobe is then fabricated by co‐loading of 3,3,5,5‐tetramethylbenzidine (TMB) and IR780 dye on FeWO X NSs to enable ratio‐metric photoacoustic (PA) imaging of endogenous H 2 O 2 , as verified by imaging of the subcutaneous 4T1 xenograft tumor model and lipopolysaccharide (LPS)‐induced inflammation model. Moreover, FeWO X NSs could also be employed as promising nanoagents for multimodal computed tomography (CT) and magnetic resonance (MR) imaging of tumors, due to the strong X‐ray attenuation ability of W element and high MR contrast ability of Fe element, respectively. Importantly, FeWO X NSs with good biodegradability could be cleared out from the body without any significant biotoxicity. This work highlights bimetallic oxide FeWO X NSs as an enzyme‐mimetic nanoplatform for imaging of the tumor microenvironment.