Lysosome-targeting and legumain-triggered ⁶⁸Ga-labeled probe for enhanced tumor PET imaging

Legumain is overexpressed in diverse tumors, serving as a significant tumor biomarker. Our study aimed to develop a new positron emission tomography (PET) probe [⁶⁸Ga]Ga-NOTA-SF-AANM for imaging the expression level of legumain in vivo. The radio-labeling of [⁶⁸Ga]Ga-NOTA-SF-AANM was accomplished within 15 min. The probe has good stability in vitro. NOTA-SF-AANM exhibited rapid response to recombinant human legumain enzyme, enabling intramolecular condensation cyclization. Cellular uptake and lysosomal co-localization experiments demonstrated that the probe was able to differentiate specifically between MDA-MB-468 and PC-3 cancer cells with varying degrees of legumain expression. PET imaging displayed a significant and persistent signal (3.59 ± 0.30 %ID/mL at 60 min) in MDA-MB-468 tumors, while PC-3 tumors exhibited lower radioactivity (1.08 ± 0.35 %ID/mL at 60 min), further validating the specific targeting of [⁶⁸Ga]Ga-NOTA-SF-AANM towards legumain. [⁶⁸Ga]Ga-NOTA-SF-AANM is a promising tool for precise diagnosis of legumain-related diseases due to its advantages in radio-labeling and accurate monitoring of legumain expression levels.