Cell chemistry captured in moving three-dimensional images
Researchers at the University of Tokyo demonstrated a way to follow chemical structures inside living cells in three dimensions without fluorescent dyes. The laboratory system records 19.2 volumes per second, roughly 400 times faster than earlier approaches. Tracking lipid droplets revealed motion that flat images can miss, although the technique remains suited to single cells and thin specimens.
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Chemical images become a moving volume
A team at the University of Tokyo, a Japanese research university, demonstrated moving three-dimensional chemical images of living cells without fluorescent labels. The experimental study, published in Nature Communications on 30 October, advances an approach previously used with relatively static samples. It uses the different ways molecular bonds absorb mid-infrared light to distinguish chemical structures inside the cell.[1], [2]
The system produces 19.2 complete volumes per second, compared with fewer than 0.05 in earlier implementations. That is an approximately 400-fold increase, with one volume taking 52 milliseconds. The researchers achieved the speed without averaging successive volumes. First author Masato Fukushima is a doctoral student in physics; senior author Takuro Ideguchi works in the university's Graduate School of Frontier Sciences.[1], [2]
Lipid droplets reveal motion through the cell
Infrared absorption creates a small temperature change, which alters how visible light passes through the sample. Combining measurements from different angles reconstructs that change in three dimensions. Faster changes in illumination angle and clearer signals in individual images helped overcome the earlier speed barrier. Avoiding added dyes also removes a potential source of harm to living samples.[1], [2]
In living cells derived from monkey kidney tissue, the team followed lipid droplets, which participate in lipid storage and energy regulation. Their paths differed across directions. Movement along the depth axis can disappear in a flat image, making intracellular transport appear smaller than it is. The demonstration followed the droplets through the cell's volume rather than just across an image plane.[1], [2]
Water and scattering constrain thicker specimens
A separate experiment in fixed cells distinguished nucleoli and small lipid-rich structures through their responses at different infrared wavenumbers. These spectral signatures give an approximate chemical description within a chosen reference model. The fitted contributions should not be read as absolute molecular concentrations or molar fractions. The results concern chemical imaging in laboratory samples, rather than a tested clinical diagnostic application.[1]
The platform is suited to single cells and thin specimens. Water strongly absorbs infrared light, while visible light scatters in thicker tissue, restricting extension to larger samples. The researchers identify longer observations of droplet formation, fusion and transport as possible future applications. Membrane-free cellular structures containing proteins and nucleic acids are also among the subjects they hope to investigate.[1], [2]
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