A General Strategy to Develop Highly Sensitive FAPα Fluorescent Probes for Invasive Cancer Detection

Fibroblast activation protein α (FAPα) has been reported to be expressed in many carcinoma cells and associated with tumor growth, invasive, and metastasis. However, due to the lack of appropriate fluorescent probes, detecting FAPα with high sensitivity in tumor and clearly delineating tumor margins remains a challenge. Herein, we developed a general design strategy-introducing a positive charge into the fluorophore skeleton-for the construction of FAPα-activated fluorescent probe with enhanced sensitivity. Molecular docking simulations and fluorescence spectra revealed that the FAPα-activated fluorescent probe with positive charges displayed an improved affinity and sensitivity toward FAPα. As demonstration, FQCy7, featuring two positive charges, NIR fluorescence emission, and large Stokes shift, exhibited a satisfactory sensitivity toward FAPα and was used for the relationship study between FAPα and carcinoma cell migration and invasion. Furthermore, we have demonstrated, for the first time, that FQCy7 is highly useful in distinguishing invasive tumor from benign lesions and evaluating the precise resection of tumor tissues. This work not only reports an original strategy to design FAPα-activated fluorescent probes with high sensitivity but also provides a powerful tool for precise tumor detection.