PERSPECTIVES
FOLDING DNA
circular dichroism( CD), defined as the differential absorption of leftand right-circularly polarized light. In natural biomolecules, CD signals are generally weak and confined to the ultraviolet spectral range. By contrast, metallic NPs arranged in three-dimensional chiral geometries support collective plasmonic modes that generate CD responses in the visible and near-infrared, often several orders of magnitude stronger than those observed in molecular systems.
The fabrication of such architectures is challenging using conventional top-down methods, which are inherently planar and offer limited access to fully three-dimensional geometries. DNA origami provides a powerful alternative by acting as a fully addressable molecular scaffold capable of organizing metallic nanostructures into prescribed chiral arrangements. [ 8 ] For example, spherical gold NPs can be assembled into left- and right-handed helices, [ 9 ] tetramers, or toroidal structures with nanometer precision. Although the individual particles are achiral, their collective arrangement breaks mirror symmetry and produces strong, programmable CD signals whose spectral position can be tuned through the particle size, spacing, and overall geometry.
The optical response can be further enhanced by replacing spherical particles with anisotropic plasmonic elements such as gold nanorods. One of the most widely studied configurations consist of positioning two nanorods on opposite faces of a DNA origami template with a well-defined dihedral angle, forming a chiral plasmonic cross. The electromagnetic coupling between the longitudinal plasmon modes of the rods gives rise to pronounced bisignate CD spectra and provides a model system for studying nanoscale chiral light-matter interactions. [ 10 ]
Beyond static structures, DNA nanotechnology offers a unique opportunity to create reconfigurable chiral photonic systems. By incorporating responsive DNA elements into the origami design, the relative orientation of the plasmonic components can be modified after assembly, enabling the optical activity of the structure to be switched. In a representative example, light-induced hybridization and dehybridization were used to reversibly lock a plasmonic nanorod cross into either a chiral or an achiral state. [ 10 ] Similar concepts have been implemented using pH-responsive DNA motifs, allowing reversible modulation of plasmonic chirality through simple chemical stimuli. [ 11 ] These systems illustrate how DNA origami can transform plasmonic nanostructures from static objects into dynamic photonic devices whose optical properties are controlled at the molecular level.
CONCLUSION DNA origami has emerged as a versatile bottom-up nanofabrication platform for nanophotonics. By exploiting the programmability of DNA self-assembly, it provides a molecular scaffold in which optical components such as fluorophores, metallic NPs, and dielectric nanostructures can be positioned with nanometer precision and controlled stoichiometry. This level of control complements conventional top-down fabrication
REFERENCES
[ 1 ] P. W. K. Rothemund, Nature 440, 297( 2006) [ 2 ] A. Kuzyk et al., ACS Photonics 5, 1151( 2018) [ 3 ] A. K. Adamczyk et al., ACS Photonics 11, 5272( 2024) [ 4 ] M. Yesilyurt et al., ACS Nano 17, 19189−19196( 2023) [ 5 ] N. Siegel et al., J. Am. Chem. Soc. 146, 17250( 2024) [ 6 ] N. Siegel et al., Small Struct. 6, 2500299( 2025) [ 7 ] G. P. Acuna et al., ACS Nano 6, 3189( 2012) [ 8 ] C. Zhou, X. Duan, and N. Liu, Acc. Chem. Res. 50, 2906( 2017) [ 9 ] R. Schreiber et al., Nat. Commun. 4, 2948( 2013) [ 10 ] A. Kuzyk et al., Nat. Commun. 2016 71 7, 10591( 2016) [ 11 ] A. Kuzyk et al., Sci. Adv. 3, e1602803( 2017) approaches and enables experiments that would be difficult to realize using lithographic methods alone.
DNA origami has enabled the realization of a wide range of nanophotonic architectures. The ability to position individual emitters with respect to optical antennas has provided new opportunities to investigate light-matter interactions at the single-molecule level. At the same time, the assembly of metallic and dielectric NPs into well-defined geometries has opened routes toward engineered emission, directional radiation, and chiral optical responses. Beyond static structures, the intrinsic programmability of DNA also allows the fabrication of dynamically reconfigurable systems whose optical properties can be modulated by molecular or chemical stimuli.
Although challenges remain, particularly regarding robustness, largescale manufacturing, and integration into practical devices, DNA-origamibased nanophotonics has matured from a proof-of-concept technology into a powerful experimental platform. By bridging molecular self-assembly and photonic engineering, it continues to provide new ways to design, fabricate, and study optical systems with an unprecedented level of structural control.
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