DNA origami nanolenses visualize single modules

Ashley N. Rice, ashley.rice@photonics.com

Self-assembling nanolenses that use DNA as a construction material represent a better way of visualizing single molecules and could help unlock biological processes such as DNA transcription or replication at the single-molecule level.

Drs. Guillermo Acuna and Philip Tinnefeld of the Institute for Physical and Theoretical Chemistry at Technical University Braunschweig led the interdisciplinary group that used DNA origami – a nanostructure foundation process developed in 2006 – to create a scaffold for its nanoantenna.

A new self-assembling nanolens that uses DNA as a construction material can visualize single molecules. Here, the DNA origami nanopillar (in gray) is immobilized on a coverslip. Two 80- to 100-nm-diameter gold nanoparticles serve as nanoantennae and focus the light in the hot spot between the nanoparticles. A fluorescent dye attached in the hot spots acts as an active optical source and reports on the fluorescence enhancement. Courtesy of TU Braunschweig.

Overlapping plasmonic fields between gold nanoparticles act as nanoantennae to focus light far beyond the diffraction limit. Such tight focusing could boost the sensitivity of biotech applications.

“In particular, we would like to observe enzymatic processes in which a high concentration of dye-labeled molecules are required ... for example, DNA sequencing,” Acuna and Tinnefeld told BioPhotonics in an email.

Until now, the challenge has been in placing the gold particles, with their dimensions of 80 to 100 nm, at a defined distance and bringing molecules being investigated into the “hot spot” between the particles.

Although other single-molecule visualization techniques exist, they are complex and expensive. The team says its self-assembly approach can produce many nanolenses quickly and cheaply, and that the technique could affect a broad range of research disciplines.

Analogy between a conventional lens (left) focusing a light beam and the nanolens (right) made with two spherical gold nanoparticles on a DNA origami pillar structure. The nanolens can focus the light beam between the particles in an extremely reduced volume. Courtesy of Agustin Acuna.

“There are mostly two ‘fields’ of applications: one more fundamental research on plasmonic and nanophotonics, since, with this technique, dyes can be placed in close proximity to different nanoparticle arrangements with nanometric precision; the other field points toward biomolecular applications,” Acuna and Tinnefeld wrote in their email.

Next, the team intends to increase the fluorescence enhancement, either by decreasing the gap size between nanoparticles or by placing particles with different shapes into the scheme. They also hope to increase the biomolecular compatibility by increasing and optimizing the space between the nanoparticles.

The findings were reported in Science (doi: 10.1126/science.1228638).