β-galactosidase instructed in situ self-assembly fluorogenic probe for prolonged and accurate imaging of ovarian tumor.

Fluorescent probes are essential for optical imaging and have been extensively employed for precise cancer diagnosis studies. β-galactosidase (β-gal) serves as a primary biomarker for ovarian cancer and has been utilized to develop imaging probes for accurate tumor diagnosis. However, traditional small molecular probes have limitations in terms of rapid diffusion and metabolic clearance from the target lesion, resulting in a short imaging window and compromised tumor-to-background ratios (TBR). Herein, we integrated an enzyme-instructed in situ self-assembly strategy to construct Gal-IRFF, a small molecule-based activatable near-infrared (NIR) fluorogenic probe. Upon cleavage by endogenous β-gal overexpressed in ovarian cancer cells, IRFF exhibited enhanced NIR fluorescence signals and self-assembled into nanoparticles through intermolecular interactions of the Phe-Phe (FF) dipeptide moiety, which facilitated probe accumulation and retention within the tumor lesion. Compared with the small molecule probe Gal-IR, our proposed self-assembly probe Gal-IRFF demonstrated a lower limit of detection (LOD) towards β-gal and showed remarkable improvements in distribution and retention time within SKOV3 cells in vitro and tumors in vivo, thereby providing a long-term imaging window for real-time monitoring β-gal levels in ovarian tumors. Therefore, this study highlights the potential of an enzyme-instructed self-assembly fluorogenic probe design approach for achieving precise tumor diagnosis in vivo.