Intra-nanoparticle plasmonic nanogap based spatial-confinement SERS analysis of polypeptides

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Biophysics

Background:

• Sensing water-soluble polypeptides is crucial for biological applications.
• Current Surface-Enhanced Raman Scattering (SERS) methods struggle to detect non-aromatic amino acids due to signal interference from aromatic residues and backbones.
• A need exists for sensitive and specific polypeptide detection techniques.

Purpose of the Study:

• To design and synthesize novel intra-nanoparticle plasmonic nanogaps for enhanced SERS detection of polypeptides.
• To develop a controllable and generalizable strategy for fabricating these nanostructures with tunable electric field enhancement.
• To demonstrate the capability of the developed SERS substrate for simultaneous and sensitive detection of multiple polypeptide molecules.

Main Methods:

• Fabrication of AuAg@void@Au nanoparticles by etching Ag shells in Au@AgNPs with chlorauric acid.
• Tuning nanoparticle properties by varying molar ratios of silver to chloroauric acid.
• Encapsulation and spatial confinement of polypeptide molecules (bacitracin and insulin B) within the intra-nanogap for SERS analysis.

Main Results:

• Successful synthesis of interlayer-free nanoparticles with tunable shell thickness and precisely regulated electric field enhancement.
• Demonstrated simultaneous encapsulation and detection of bacitracin and insulin B within the intra-nanogap.
• Achieved improved sensitivity and more comprehensive characteristic peaks for polypeptides compared to conventional SERS substrates (AuNPs and Au@AgNPs).

Conclusions:

• The developed intra-nanoparticle plasmonic nanogap strategy offers a highly sensitive and specific method for polypeptide detection.
• The fabrication approach allows for precise control over plasmonic properties and analyte confinement.
• This technique eliminates the need for labeling and provides a robust platform for peptide analysis and potential sequencing.