A compartment-free digital plasmonic coupling assay via single-particle imaging and counting

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Analytical Chemistry

Background:

• Conventional plasmonic biosensors rely on bulk measurements, limiting sensitivity due to high background noise.
• Existing detection methods often require complex chip or droplet compartments for analysis.

Purpose of the Study:

• To develop a digital plasmonic assay platform for sensitive biomarker detection.
• To overcome the limitations of bulk measurement methods in plasmonic biosensing.
• To enable digital quantification of individual nanoparticle clusters for enhanced assay sensitivity.

Main Methods:

• Utilized a digital plasmonic assay platform based on gold (Au) and silver (Ag) nanoparticles (NPs).
• Employed single-nanoparticle darkfield scattering imaging to enumerate individual plasmon-shifted nanoclusters.
• Investigated nanoparticle-protein interactions and performed Finite-Difference Time-Domain (FDTD) simulations for plasmonic coupling effects.
• Developed a particle counting algorithm for accurate quantification of nanoparticle clusters.

Main Results:

• Achieved a limit of detection (LOD) of 107.5 fM for biotinylated gold nanoparticles under optimized conditions.
• Demonstrated digital enumeration of nanoparticle clusters without complex compartments.
• FDTD simulations provided insights into plasmonic coupling effects of various NP combinations.
• Validated a particle counting algorithm for high-accuracy quantification of clusters.

Conclusions:

• The developed digital plasmonic assay platform enables sensitive biomarker detection through digital enumeration of individual nanoclusters.
• This assay overcomes background noise limitations of conventional bulk measurement methods.
• The platform shows potential for high-sensitivity protein target detection in disease diagnostics.