Ligand-functionalized core/shell Ag@Au nanoparticles label-free amperometric immun-biosensor

Area of Science:

• Nanotechnology
• Electrochemistry
• Immunotechnology

Background:

• Immunoassays are crucial for disease diagnosis.
• Traditional methods often involve complex labeling and separation steps.
• Developing sensitive and direct detection methods is essential.

Purpose of the Study:

• To develop a novel label-free electrochemical immunoassay for immunoglobulin G (IgG) detection.
• To utilize a core/shell silver-gold (Ag@Au) nanoparticle monolayer as a sensing interface.
• To compare different coupling techniques for optimizing immunoassay performance.

Main Methods:

• Fabrication of a core/shell Ag@Au nanoparticle monolayer sensing interface.
• Investigation of L-Cysteine cross-linking for enhanced antibody immobilization.
• Electrochemical detection of IgG using amperometry.
• Optimization of incubation time and pH for signal response.
• Validation against Enzyme-Linked Immunosorbent Assay (ELISA) using human serum samples.

Main Results:

• The core/shell Ag@Au nanoparticles with L-Cysteine cross-linking showed superior performance compared to other methods.
• The immunoassay demonstrated an excellent storage lifetime of 33 days.
• A wide dynamic concentration range (2.3–960 ng/mL) with a low detection limit (10 ng/mL) was achieved.
• Results from human serum samples showed satisfactory agreement with ELISA.

Conclusions:

• The developed label-free electrochemical immunoassay is highly sensitive, stable, and reliable for IgG detection.
• The core/shell Ag@Au nanoparticle monolayer provides an effective sensing platform.
• This method offers advantages of being direct, rapid, and simple, avoiding multiple separation and labeling steps.