Gold-Silver Core-Shell Nanoparticle Crosslinking Mediated by Protease Activity for Colorimetric Enzyme Detection

Area of Science:

• Nanotechnology
• Biochemistry
• Spectroscopy

Background:

• Plasmonic nanoparticles exhibit localized surface plasmon resonance (LSPR), leading to observable color changes with environmental shifts.
• The optical properties of nanoparticles are highly sensitive to their dielectric surroundings and aggregation state.
• Gold-silver core-shell nanoparticles offer tunable optical properties for sensing applications.

Purpose of the Study:

• To investigate the optical shifts of gold-silver core-shell nanoparticles in response to aggregation.
• To explore how peptide structure, specifically proline spacers, influences nanoparticle aggregation and optical response.
• To develop a colorimetric enzyme assay utilizing nanoparticle aggregation for sensitive enzyme detection.

Main Methods:

• Synthesis and characterization of unique gold-silver core-shell nanoparticle structures.
• Induction of nanoparticle aggregation using cysteine-containing peptides with varying proline spacer lengths.
• Spectroscopic analysis of optical shifts (color change) correlated with nanoparticle aggregation.
• Development and validation of a colorimetric enzyme assay based on proteolysis-modulated aggregation.

Main Results:

• Demonstrated distinct optical shifts in gold-silver core-shell nanoparticles upon aggregation.
• Showcased that proline spacers modulate the degree of aggregation and the resulting colorimetric response.
• Established a linear correlation (R^2 = 0.998) between optical shift and enzyme concentration.
• Achieved a spectral limit of detection (LOD) of 0.47 ± 0.09 nM for enzyme activity.

Conclusions:

• Gold-silver core-shell nanoparticles serve as effective colorimetric indicators for aggregation.
• Peptide-mediated aggregation offers a controllable mechanism for tuning nanoparticle optical properties.
• The developed assay provides a sensitive and linear method for enzyme quantification.
• This work highlights the potential of plasmonic nanoparticles in developing advanced biosensing platforms.