Fe-N₃S Single-Atom Nanozyme with Asymmetric Coordination for Ultra-Low-Background Colorimetric Immunoassays

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Analytical Chemistry

Background:

• Nanocatalysts enhance immunoassay sensitivity for low-abundance proteins.
• Nonspecific reactions in nanocatalysts lead to high background signals and false positives, limiting their use.

Purpose of the Study:

• To design and synthesize a single-atom nanozyme with a modulated catalytic pathway to overcome background interference in immunoassays.
• To develop a highly sensitive and specific immunochromatographic sensor for protein detection.

Main Methods:

• Asymmetric coordination field modulation strategy to synthesize Fe-N3S single-atom nanozymes.
• Density functional theory (DFT) calculations to elucidate catalytic mechanisms.
• Development of a cascade catalytic reaction-based immunochromatographic sensor.

Main Results:

• Fe-N3S nanozymes exhibited high peroxidase-like (POD) activity and low oxidase-like (OXD) activity, unlike Fe-N4 nanozymes.
• DFT revealed sulfur's role in disrupting symmetry and lowering the energy barrier for the POD pathway.
• The developed immunochromatographic sensor achieved a low limit of detection (0.69 pg mL-1) for CD40L with high specificity and stability.

Conclusions:

• The Fe-N3S nanozyme's unique catalytic pathway effectively minimizes background interference.
• This work presents a promising platform for developing portable, low-background colorimetric immunosensing methods.
• The strategy opens new avenues for sensitive and specific detection of biomarkers.