Ratiometric Photoacoustic Imaging Probe for Self-Predicting Nanozyme Therapeutic Effects

Nanozymes with intrinsic enzyme-like properties have garnered significant attention in cancer treatment. However, effective methods to evaluate in situ the catalytic activity of nanozymes in living systems remain lacking. Herein, we pioneeringly present a novel probe (1-FCuSA) for self-reporting nanozyme catalytic activity, which integrates a diene electrochromic material (EM 1) and a copper single-atom nanozyme (FCuSA) with peroxidase (POD)-like activity. This system is designed to self-predict its catalytic activity through a ratiometric photoacoustic (PA) imaging signal. Initially, 1-FCuSA exhibits a low PA ratio (PA₈₀₈/PA₁₀₆₄) between 808 and 1064 nm. Upon reaction with hydroxyl radicals (•OH) generated by the POD-like activity of FCuSA, the PA signal at 808 nm significantly increases, while the signal at 1064 nm remains stable. This results in an obvious increase in PA₈₀₈/PA₁₀₆₄, enabling accurate monitoring of •OH production during nanozyme-catalyzed therapy. Thus, 1-FCuSA not only induces specific POD-like activity for in vivo tumor treatment but also provides real-time monitoring of catalytic efficiency through ratiometric PA imaging. This innovative approach may offer new insights into the early prediction of anticancer efficacy and guide the application of nanozymes in living systems.