Jian-An's abstract is accepted as invited oral presentation in the BIOSENSOR 2021 conference

Title: Single-Molecule Detection of DNA and Proteins in a Plasmonic Nanopore by Surface Enhanced Raman Spectroscopy (SERS)

Abstract: Surface-enhanced Raman spectroscopy (SERS) as a powerful label-free detection method with single-molecule sensitivity could pave a way to new generation single-protein sequencing platforms. While many single-molecule SERS substrates work in dry status, biomedical applications of SERS need to be in solution phase and encounter many challenges. Most solution-phase colloid SERS systems rely on the instantly-formed colloid clusters to achieve single-molecule sensitivity of dye molecules under resonant Raman conditions. However, single-molecule SERS detection of nucleobases and amino acids that have Raman cross-sections ~100 times smaller than those of dyes were not demonstrated in solution phases. Furthermore, colloid clusters flow so rapidly in solution that the SERS signals collected are not sufficient for single-molecule analysis.

Here, we report an electro-plasmonic trapping approach (Figure 1a-c) to control the time that molecules reside in single hot spot in fluid by adsorbing them onto a gold nanoparticle and then trapping the single nanoparticle in a plasmonic nanopore.1 The electro-plasmonic trapping is due to a balance between the electrophoretic (EP), electroosmotic (EO), and optical forces (OF) (Figure 1d). The optical force pulls a gold nanostar (AuNS) near the nanohole sidewall upon laser excitation. As a result, it induces a plasmonic hot spot on the AuNS tip that has a small size comparable to an amino acid and strong intensity capable of single-molecule SERS sensing (Figure 1e).2 By trapping the AuNS for up to minutes, we demonstrate single-molecule SERS detections of single nucleobases in a single oligonucleotide (Figure 2) and single amino acid residues in a single polypeptide (Figure 3) in liquid for the first time. Correlated with Molecular Dynamics simulation, our experiment further monitors conformation dynamics of single polypeptide on the AuNS (Figure 3a,b).2 Our method show potentials for single-protein analysis and sequencing.

References:

1. Huang, J.-A.; Mousavi, M. Z.; Zhao, Y.; Hubarevich, A.; Omeis, F.; Giovannini, G.; Schütte, M.; Garoli, D.; De Angelis, F., SERS discrimination of single DNA bases in single oligonucleotides by electro-plasmonic trapping. Nature Communications 2019,10 (1), 5321.

2. Huang, J.-A.; Mousavi, M. Z.; Giovannini, G.; Zhao, Y.; Hubarevich, A.; Soler, M. A.; Rocchia, W.; Garoli, D.; De Angelis, F., Multiplexed Discrimination of Single Amino Acid Residues in Polypeptides in a Single SERS Hot Spot. Angewandte Chemie International Edition 2020, 59 (28), 11423-11431.