A neutrophil elastase-responsive NIR-II fluorescent probe for simultaneous cell and tumor visualization and...

Neutrophil elastase (NE), a typical serine protease mainly secreted by tumor-associated neutrophils (TANs), plays significant roles in tumor growth, invasion, and metastasis, and is thus regarded as a critical cancer biomarker. Therefore, developing reliable analytical methods for monitoring NE activity in biological systems is crucial for tumor diagnosis and intraoperative assisted resection. Herein, based on the intramolecular charge transfer (ICT) mechanism, we designed an NE-activatable probe (CNHcy-NE) for second near-infrared window (NIR-II) fluorescence imaging of NE in vivo. CNHcy-NE was synthesized by conjugating a hemicyanine dye to a perfluoropropionic amide-based NE substrate via a p-aminobenzyl alcohol linker. The probe exhibited high selectivity and sensitivity to NE with a detection limit of 2.36 U/L. Probe CNHcy-NE was successfully applied to monitor NE activity and visualize NE regulation at the cellular level. Moreover, it demonstrated the ability to discriminate tumor tissues from adjacent normal tissues via NIR-II fluorescence imaging and to guide surgical resection in mice models. These findings suggest the potential of CNHcy-NE as a promising tool for practical applications in NIR-II imaging-guided pancreatic ductal adenocarcinoma (PDAC) surgery.