High-Speed Raman Readout of Single Polypeptides via Plasmonic Nanopores

Area of Science:

• Nanotechnology
• Spectroscopy
• Biomedical Diagnostics

Background:

• Label-free protein identification is crucial for biomedical diagnostics.
• Surface-Enhanced Raman Scattering (SERS) requires signal amplification for single-molecule detection due to small Raman cross-sections.
• Existing SERS methods face limitations in sensitivity and resolution.

Purpose of the Study:

• To develop a novel approach for label-free, single-molecule protein identification using SERS.
• To fabricate stable and cost-effective plasmonic nanopores for sequential Raman readout.
• To achieve real-time, high-resolution molecular detection.

Main Methods:

• Fabrication of plasmonic nanopores using Capillary-Assisted Particle Assembly (CAPA) of gold nanoparticles (Au NPs).
• Electrophoretic driving of polypeptides through nanopores for sequential Raman spectroscopy.
• Real-time detection using a Single-Photon Avalanche Diode (SPAD) camera.

Main Results:

• Achieved single-molecule detection at 1 nM concentration with 100 microsecond resolution.
• Demonstrated a linear correlation between dwell time, molecular length, and Raman signal intensity.
• Recorded an average of 6 photons/amino acid and 7 µs translocation time per amino acid.

Conclusions:

• The developed method enables sequential Raman readout, overcoming key limitations of traditional SERS.
• This represents a significant advancement toward label-free, high-resolution molecular identification.
• The technique holds potential for future applications in protein identification and analysis.