Researchers at the University of Tokyo have introduced a breakthrough in high-speed microscopy that allows for the capture of three-dimensional images of living cells at unprecedented speeds. Published in Nature Communications, the study details a new technique capable of generating "videos" of dynamic processes occurring inside cells by acquiring images nearly 400 times faster than prior efforts.
The team utilized mid-infrared light to create photothermal signals, capturing snapshots of temperature-change signatures emitted by different molecules within the cell. This label-free approach avoids the use of dyes, which can be toxic to live samples, while still allowing for the mapping of internal cellular composition based on distinctive chemical bond frequencies. By illuminating the sample with visible light after vibrating these bonds, researchers can visualize the chemical makeup of the cell.
Previous methods for three-dimensional mid-infrared photothermal tomography were limited to less than 0.05 images per second due to the time required for signal averaging and sequential measurements from various angles. The new technique, termed video-rate mid-infrared photothermal optical diffraction tomography (MIP-ODT), achieves a rate of 19.2 images per second. This speed allows the system to acquire a complete three-dimensional image every 52 milliseconds.
Masato Fukushima, the study's first author and a Ph.D. student in the Department of Physics, explained that the team overcame previous speed barriers by employing a spatial light modulator. This device precisely shapes light properties to steer illumination angles rapidly while maximizing the signal-to-noise ratio for each shot. The result transforms the technique from a tool for observing static samples into one capable of quantitatively investigating fast biological processes in three dimensions.
Using MIP-ODT, the researchers successfully tracked lipid droplets responsible for energy regulation and lipid storage as they moved through three-dimensional space. This capability revealed transport behaviors that are difficult to detect with two-dimensional imaging alone. The team envisions future applications in studying biomolecular condensates, membraneless structures containing proteins and nucleic acids whose abnormal behavior is linked to neurodegenerative disorders.
Takuro Ideguchi, the study's senior author and a professor at the Graduate School of Frontier Sciences, highlighted the potential for addressing fundamental biological questions. He noted that the label-free nature of the imaging provides quantitative information about chemical composition, aiming to advance toward a measurement-driven understanding of life by visualizing cellular dynamics over time.
Sources: Phys.org.