Lysosome-Targeting Fluorogenic Probe for Cathepsin B Imaging in Living Cells

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Research

Background:

• Cathepsin B (CTB) is a lysosomal protease and a potential biomarker for various cancers.
• Accurate detection of CTB activity is crucial for early cancer diagnosis and metastasis prediction.

Purpose of the Study:

• To develop a lysosome-targeting fluorogenic small-molecule probe for fluorescence imaging of lysosomal CTB in living cancer cells.
• To enable sensitive and specific detection of CTB activity for cancer diagnostics.

Main Methods:

• Incorporation of a CTB-recognitive peptide substrate (Cbz-Lys-Lys-PABA) and a lysosome-locating morpholine group into a small-molecule probe.
• Activation of the probe by CTB in acidic lysosomal environments (pH 4.5-6.0) leading to fluorescence enhancement.
• Fluorescence imaging in living cancer cells and normal tissue cells.

Main Results:

• The probe exhibited approximately 73-fold fluorescence enhancement upon activation by CTB.
• High sensitivity and specificity for CTB detection were achieved.
• Selective accumulation and fluorescence turn-on were observed in the lysosomes of cancer cells, enabling visualization of CTB activity.

Conclusions:

• The developed lysosome-targeting probe is effective for sensitive and specific fluorescence imaging of lysosomal CTB in living cells.
• This probe holds potential for improving early cancer diagnosis and metastasis prediction.
• Lysosome-targeting strategies can enhance the design of sensitive probes for intracellular enzyme activity imaging.