Rapid cooling technique increases nanoparticle beam density for imaging

Single-particle diffractive imaging using X-ray free-electron lasers allows researchers to reconstruct the structure of nanoparticles. However, the technique often requires up to several billion nanoparticles to produce the image and imposes limitations on its clarity and sharpness. Samanta et al. demonstrate a method for generating reproducible, high-density beams of nanoparticles for single-particle diffractive imaging.

Using a cryogenic cell containing cold helium gas, the authors froze nanoparticles in microseconds – much faster than current state-of-the-art processes – and prevented them from denaturing. This resulted in a reproducible, high-density particle beam that could be imaged directly using a single-particle localization microscope. They also developed a simulation technique corroborated by their experimental results for the analysis of the nanoparticle distribution in the beam.

The method mitigates the reproducibility problem inherent in single-particle diffraction imaging by allowing the beams to be further manipulated for follow-up experiments.

According to author Jochen Küpper, the group plans to continue tuning the parameters in their setup, so that they can apply their findings to smaller systems such as biological macromolecules.

“Beams of cold isolated nanoparticles and biological macromolecules open up a large toolbox of control methods, originally developed for cold small gas-phase molecules, to large nanoscale systems,” Küpper said. “[The] ability to control particles’ final temperature and cooling rate will allow exploration of temperature dependent phenomena in biological and artificial nanoparticles.”

Source: “Controlled beams of shock-frozen, isolated, biological and artificial nanoparticles,” by Amit K. Samanta, Muhamed Amin, Armando D. Estillore, Nils Roth, Lena Worbs, Daniel A. Horke, and Jochen Küpper, Structural Dynamics (2020). The article can be accessed at https://doi.org/10.1063/4.0000004 .