Split-GFP: SERS Enhancers in Plasmonic Nanocluster Probes

Area of Science:

• Nanotechnology
• Biophysics
• Spectroscopy

Background:

• Plasmonic metal nanoparticles form hot spot surface-enhanced Raman scattering (SERS) nanocluster probes for ultrasensitive biosensing.
• Self-complementary peptides and proteins are emerging as scaffolding strategies for these assemblies.
• Predicting and optimizing the electronic and photonic properties of hybrid nanoclusters remains challenging.

Purpose of the Study:

• To utilize split-green fluorescence protein (sGFP) fragments as molecular glue and the GFP chromophore as a Raman reporter.
• To assemble gold nanoparticle (AuNP) clusters and explore their plasmonic properties via numerical modeling.
• To provide rationales for optimizing hot spot SERS nanoprobe assembly for remote biosensing.

Main Methods:

• Assembly of AuNP clusters using sGFP fragments as molecular glue.
• Numerical modeling to explore plasmonic properties of AuNP/GFP hybrid nanoclusters.
• Investigating SERS enhancement factors and near-field couplings in different nanocluster configurations.

Main Results:

• GFP seeding in plasmonic nanogaps of AuNP/GFP nanoclusters enhances near-field dipolar couplings.
• SERS enhancement factors exceeding 10⁸ were achieved.
• AuNP/GFP chains demonstrated near-infrared SERS detection with enhancement factors of 10⁸ -10⁹.
• Excessive clustering reduced SERS amplification due to non-GFP seeded nanogaps.

Conclusions:

• sGFP acts as an effective molecular glue for assembling AuNP clusters for SERS biosensing.
• Controlled assembly, particularly AuNP/GFP chains, optimizes SERS enhancement factors.
• Understanding nanogap influence is crucial for designing efficient hot spot SERS nanoprobes.