Circular Dichroism of Chiral Molecules in DNA- Assembled Plasmonic Hotspots

TL;DR

This study demonstrates that placing chiral molecules like DNA within plasmonic hotspots significantly enhances circular dichroism signals across a broad spectrum, aiding sensitive detection of molecular chirality for drug development.

Contribution

The paper introduces a method to amplify UV circular dichroism signals by positioning DNA molecules in plasmonic hotspots, extending detection into the near-infrared range.

Findings

Enhanced CD transfer efficiency with different nanoparticle types.

Demonstrated CD transfer over the entire optical spectrum.

Supported experimental results with theoretical models.

Abstract

The chiral state of a molecule plays a crucial role in molecular recognition and biochemical reactions. Because of this and owing to the fact that most modern drugs are chiral, the sensitive and reliable detection of the chirality of molecules is of great interest to drug development. The majority of naturally occurring biomolecules exhibit circular dichroism (CD) in the UV-range. Theoretical studies and several experiments have demonstrated that this UV-CD can be transferred into the plasmonic frequency domain when metal surfaces and chiral biomolecules are in close proximity. Here, we demonstrate that the CD transfer effect can be drastically enhanced by placing chiral molecules, here double-stranded DNA, inside a plasmonic hotspot. By using different particle types (gold, silver, spheres and rods) and by exploiting the versatility of DNA origami we were able to systematically study the impact of varying particle distances on the CD transfer efficiency and to demonstrate CD transfer over the whole optical spectrum down to the near infrared. For this purpose, nanorods were also placed upright on our DNA origami sheets, this way forming strong optical antennas. Theoretical models, demonstrating the intricate relationships between molecular chirality and achiral electric fields, support our experimental findings.