Gold Nanoparticles-Based Colorimetric Assay for Cathepsin S Activity.

Area of Science:

• Biochemistry
• Nanotechnology
• Assay Development

Background:

• Cathepsin S (CatS) is a cysteine protease involved in antigen presentation and implicated in diseases like Alzheimer's, atherosclerosis, and obesity.
• A selective and simple method for detecting CatS activity is essential for research and potential therapeutic targeting.

Purpose of the Study:

• To develop a novel colorimetric assay for the selective and straightforward detection of Cathepsin S (CatS) activity.
• To utilize gold nanoparticles (AuNPs) and CatS-specific peptides for a visual detection method.

Main Methods:

• A colorimetric assay was designed using gold nanoparticles (AuNPs) stabilized by CatS-specific peptides (PMGAPC or PMGAPC-NH2).
• CatS enzyme activity was detected by observing the aggregation of AuNPs, indicated by a color change from red to blue upon peptide hydrolysis.
• Optimization of AuNP size and peptide concentration was performed to determine the assay's sensitivity.

Main Results:

• The CatS enzyme cleavage peptides (PMGAPC or PMGAPC-NH2) effectively stabilized AuNPs, preventing aggregation in solution.
• Hydrolysis of the peptides by CatS triggered AuNP aggregation, resulting in a visible red-to-blue color change.
• The optimized assay achieved a limit of detection of 10 nM for CatS activity using either peptide.

Conclusions:

• A selective and simple colorimetric assay for CatS detection has been successfully developed using AuNPs and specific peptides.
• The assay provides a naked-eye detectable signal, making it a valuable tool for CatS activity monitoring in relevant disease research.
• This method offers a promising approach for studying CatS in biological and clinical contexts.