Microscope design promises breakthrough in 3D single-particle tracking

Molecular actions are notoriously difficult to divorce from their surroundings. The challenge of tracking particles in 3D at high speeds in high-background settings has long been a source of frustration for chemical physicists and others interested in chemical dynamics in complex environments.

To potentially alleviate the frustration, Zhao et al. showcase a microscopy platform featuring a hardware-based time-gating module that enables photon processing rates to be as high as 100 megahertz -- in contrast to just 200 hertz demonstrated in previous work.

“Here, we show we can track, in 3D and in real time, nanoscale particles in noisy environments such as biological cells and complex materials,” said co-author Tian Zhao. “This is done at the hardware level based on real-time single-photon analysis. This work demonstrates it is possible to investigate fast dynamics in high-background complex systems, a feat difficult to do previously.”

The instrument employs a two-photon 3D single-particle tracking confocal microscope that can exclude signals associated with short-lifetime background emission and scattering, enabling improved tracking stability of longer-lifetime probes. In proof-of-principle experiments, single quantum dots are tracked in solutions containing dye-stained cellulose, revealing a 33-fold improvement for particle trackability compared to previous work.

“Others may find this practical for their own research,” said Zhao.

The new microscopy platform is anticipated to be useful to various scientific communities interested in tracking single particles in cellular environments, which commonly have high fluorescence and scattering background. Coupled with other imaging and control modalities, the device may enable studies of nanoscale dynamics in biological and other complex systems that otherwise exhibit prohibitively high backgrounds.

Source: “Leveraging lifetime information to perform real-time 3D single-particle tracking in noisy environments,” by Tian Zhao, Joseph S. Beckwith, M. Junaid Amin, Marcell Pálmai, Preston T. Snee, Ming Tien, and Haw Yang, Journal of Chemical Physics (2021). The article can be accessed at https://DOI:10.1063/5.0063634 .