Single-Molecule Fluorescence Enhancement Based Detection of ATP Using DNA Origami-Assembled Au@Ag Nanostar Optical Antennas
Vishaldeep Kaur, Charanleen Kaur, Tapasi Sen
Abstract
Modulating single molecule emission of weak quantum emitters close to metallic nanostructures through plasmonic coupling interactions have uprooted the realization of plasmonic devices-based diagnostics platforms. The complex nanoscale geometries radically engineered by DNA origami technique to optimally position a single fluorophore in the vicinity of overlapping plasmonic fields of nanostructures are a benchmark to efficiently harness the coupled electromagnetic radiation. In this report, bimetallic Au@Ag nanostars (NSs) nanoantenna site-specifically arranged by DNA origami technique is employed for the fluorescence enhancement of a single Cy3 dye positioned at the interparticle gap between the nanostructures. A maximum of ∼65-fold enhancement of Cy3 dye is observed using fabricated dimeric assemblies of Au@Ag NSs. Additionally, to expand the utility of ultrasmall detection volumes of assembled dimer nanoantenna, the fluorescence enhancement of a small biologically relevant molecule is explored using crystal violet dye as the probe, attaining a maximum of ∼42-fold enhancement. Achieving significant fluorescence enhancement is a prerequisite for exploring the exciting aspects of biomolecular interactions at the single molecule level or the design of miniature photonic devices. The present work adds a new tool in the design of coupled nanoantennas exhibiting fluorescence enhancement and can be further developed for emerging applications in point of care diagnosis.