Enzyme-catalyzed molecular MR imaging of tumors

Enzymatic activity is a pivotal factor in cancer progression, necessitating the development of in vivo imaging techniques for precise enzyme localization and quantification within tumors. Magnetic resonance imaging (MRI), known for its non-invasive nature and excellent soft tissue contrast, is vital in molecular imaging. However, current molecular MRI methods need improved accuracy and sensitivity. Interest in enzyme-catalyzed MRI probes has surged due to their unique specificity and catalytic efficiency. These probes are activated by abnormal enzyme expression in lesion tissue, enabling a signal transition from inactive to active. This “OFF-to-ON” activation aims to improve tumor imaging fidelity and the target-to-background signal ratio. This review synthesizes the latest developments in enzyme-catalyzed MRI probes, focusing on three key de-sign strategies: enzyme-catalyzed self-assembly, disassembly, and distance-dependent magnetic resonance tuning. We elucidate the practical applications of these probes in tumor enzyme monitoring and address the ongoing challenges and future directions in this burgeoning field. •Enzymatic activity is pivotal in cancer progression, necessitating methods to localize and quantify enzymes in living cancer cells for cancer imaging.•Enhancement of imaging specificity and sensitivity by enzyme-catalyzed MRI probes has been summarized, paving new avenues for advanced tumor imaging techniques.•Design strategies of enzyme-catalyzed MRI probes are summarized, including self-assembly, disassembly, and distance-dependent magnetic resonance tuning (MRET), highlighting their applications in tumor imaging.•Challenges and prospects have been discussed to further advance enzyme-catalyzed MRI probes towards clinical applications.