Cathepsin B-Activated Fluorescent and Photoacoustic Imaging of Tumor.

Early diagnosis is crucial to the treatment of cancer. Cathepsin B (CTB) plays an important role in numerous cancers, which is a promising biomarker for early diagnosis of cancer. It is necessary to exploit new probes for visualization of CTB . Fluorescent/photoacoustic (FL/PA) imaging is a powerful tool for study which possesses both excellent sensitivity and spatial resolution. To our knowledge, there has been no FL/PA probe to image CTB or . Therefore, we developed two CTB-activated FL/PA probes and , which could successfully monitor CTB activity . Both two probes had excellent sensitivity and selectivity . Cell imaging showed that or could image endogenous CTB in lysosome with 6.8-fold or 5.1-fold enhancement of the FL signal and 5.8-fold or 3.4-fold enhancement of the PA signal compared to their inhibitor contrast groups. Tumor imaging further confirmed the good applicability of these two probes to monitor CTB activity with high sensitivity and spatial resolution. Moreover, the property of is superior to due to the higher catalytic efficiency of CTB toward than . We envision that our FL/PA probe will be suitable for clinical early diagnosis of CTB-related cancer in the near future.