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 FeWOX 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 FeWOX NSs exert efficient
enzyme activity to trigger catalytic decomposition of
hydrogen peroxide (H2 O2 ) 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 FeWOX NSs to enable ratio-metric photoacoustic (PA) imaging of endogenous H2 O2 , as verified by imaging of the subcutaneous 4T1 xenograft
tumor model and
lipopolysaccharide (LPS)-induced
inflammation model. Moreover, FeWOX 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, FeWOX NSs with good biodegradability could be cleared out from the body without any significant biotoxicity. This work highlights bimetallic
oxide FeWOX NSs as an
enzyme-mimetic nanoplatform for imaging of the tumor microenvironment.