Discovery of EGFR-Targeted Environment-Sensitive fluorescent probes for cell imaging and efficient tumor detection

Overexpression of human epidermal growth factor receptor (EGFR) plays an important role in several signaling pathways inside and outside the cell, especially in the processes of cell proliferation, differentiation, and death in various cancers. Due to the complexity of the structure and function of EGFR, research on the fluorescence visualization of EGFR protein visualization has proved challenging. One possible strategy for designing a receptor-targeting fluorescent probe with a switching mechanism is to introduce an environment-sensitive fluorophore into the drug ligand. Based on this strategic molecular design, we introduced two environment-sensitive small molecular fluorophores, dansyl chloride (DNS) and nitrobenzoxadiazole (NBD), to replace the morpholine group of gefitinib, achieving a series of fluorescent molecular probes bearing a switching mechanism. The GN probes exhibited prominent environment sensitivity, suggesting good performance as turn-on EGFR-targeting fluorescent ligands. The representative probe GN3 specifically responded to tumor cells overexpressing EGFR, which was validated with live-cell fluorescence imaging and in vivo xenograft tumor imaging. Ligand-induced EGFR phosphorylation in A431 cells was considerably inhibited by probe GN3, demonstrating that this probe still functions as an EGFR inhibitor. Owing to the turn-on response of GN3 to EGFR in tumor cells, and the competitive replacement behavior to the EGFR inhibitor gefitinib, these probes have the potential to be used for fluorescence imaging of cells overexpressing EGFR.