Photonic-Plasmonic Coupling Enhanced Fluorescence Enabling Digital-Resolution Ultrasensitive Protein Detection

Area of Science:

• Biophotonics
• Nanotechnology
• Biomedical Diagnostics

Background:

• Fluorophore-based assays are crucial in life sciences but often limited by weak emission intensity.
• High signal-to-noise ratios typically require numerous labeled molecules for detection.

Purpose of the Study:

• To develop a method for significantly boosting fluorophore emission intensity.
• To enable sensitive detection and digital counting of individual target molecules.

Main Methods:

• Synergistic coupling of plasmonic nanoparticle (PF) and photonic crystal (PC) modes.
• Optimally matching PF and PC resonant modes with fluorescent dye spectra.
• Characterizing a sandwich immunoassay for human interleukin-6.

Main Results:

• Achieved a 52-fold improvement in signal intensity by matching plasmonic and photonic modes.
• Enabled observation and digital counting of individual PFs, representing single target molecules.
• Demonstrated a limit of detection of 10 fg mL⁻¹ in buffer and 100 fg mL⁻¹ in human plasma.

Conclusions:

• The plasmonic-photonic coupling method dramatically enhances fluorophore signal intensity.
• This technique allows for single-molecule detection, significantly improving assay sensitivity.
• The method shows promise for advanced diagnostics, particularly for biomarkers like interleukin-6.