Split-GFP: SERS Enhancers in Plasmonic Nanocluster Probes

Taerin Chung; Tugba Koker; Fabien Pinaud

doi:10.1002/smll.201601631

Split-GFP: SERS Enhancers in Plasmonic Nanocluster Probes

Small. 2016 Nov;12(42):5891-5901. doi: 10.1002/smll.201601631. Epub 2016 Sep 8.

Authors

Taerin Chung¹, Tugba Koker¹, Fabien Pinaud^{1

2

3}

Affiliations

¹ Department of Biological Sciences, Dana and David Dornsife College of LettersArts, and Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
² Department of Chemistry, Dana and David Dornsife College of LettersArts, and Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
³ Department of Physics and Astronomy, Dana and David Dornsife College of LettersArts, and Sciences, University of Southern California, Los Angeles, CA, 90089, USA.

PMID: 27608276
DOI: 10.1002/smll.201601631

Abstract

The assembly of plasmonic metal nanoparticles into hot spot surface-enhanced Raman scattering (SERS) nanocluster probes is a powerful, yet challenging approach for ultrasensitive biosensing. Scaffolding strategies based on self-complementary peptides and proteins are of increasing interest for these assemblies, but the electronic and the photonic properties of such hybrid nanoclusters remain difficult to predict and optimize. Here, split-green fluorescence protein (sGFP) fragments are used as molecular glue and the GFP chromophore is used as a Raman reporter to assemble a variety of gold nanoparticle (AuNP) clusters and explore their plasmonic properties by numerical modeling. It is shown that GFP seeding of plasmonic nanogaps in AuNP/GFP hybrid nanoclusters increases near-field dipolar couplings between AuNPs and provides SERS enhancement factors above 10⁸ . Among the different nanoclusters studied, AuNP/GFP chains allow near-infrared SERS detection of the GFP chromophore imidazolinone/exocyclic CC vibrational mode with theoretical enhancement factors of 10⁸ -10⁹ . For larger AuNP/GFP assemblies, the presence of non-GFP seeded nanogaps between tightly packed nanoparticles reduces near-field enhancements at Raman active hot spots, indicating that excessive clustering can decrease SERS amplifications. This study provides rationales to optimize the controlled assembly of hot spot SERS nanoprobes for remote biosensing using Raman reporters that act as molecular glue between plasmonic nanoparticles.

Keywords: finite-difference time-domain modeling; gold nanoparticles; green fluorescent protein; nanogaps; surface enhanced Raman scattering.

Abstract

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