Activatable Peptides for Rapid and Simple Visualization of Protease Activity Secreted in Living Cells.

Activity-based monitoring of cell-secreted proteases has gained significant interest due to the implication of these substances in diverse cellular functions. Here, we demonstrated a cell-based method of monitoring protease activity using fluorescent cell-permeable peptides. The activatable peptide consists of anionic (EEEE), cleavable, and cationic sequences (RRRR) that enable intracellular delivery by matrix metalloproteinase-2 (MMP2), which is secreted by living cancer cells.

Colorimetric assay of matrix metalloproteinase activity based on metal-induced self-assembly of carboxy gold nanoparticles.

Among proteases, matrix metalloproteinases (MMPs) have been of significant interest because they are considered as one of the promising biomarkers in association with cancer metastasis, inflammation and other degenerative diseases. Many attempts based on the optical sensing have been made to analyze the activity of MMPs, but most of them require an expensive fluorescence readout and a labor-intensive process. To circumvent this issue, we demonstrated a simple colorimetric detection of protease activity by using carboxy gold nanoparticles (AuNPs) and histidine-containing peptides via metal-affinity coordination.

Analysis of protease activity using quantum dots and resonance energy transfer.

This review demonstrates the detection of protease activity based on the energy transfer of quantum dots (QDs). By incorporation of varying protease substrates into designed QD probes both in fluorescence resonance energy transfer (FRET) and bioluminescence resonance energy transfer (BRET) system, proteolytic activity led to changes in the energy transfer efficiency. Especially due to the superior properties of QDs, it can be served as an excellent probe for a multiplexed and high-throughput protease assay with high sensitivity.