A new analytical system combining fluorescence microscopy and mass spectrometry has enabled researchers to visualize the chemical composition of single cells with spatial precision. Developed by a team led by the University of Osaka, the method integrates an inverted microscope with a modified tapping-mode scanning probe electrospray ionization (t-SPESI) unit, allowing direct observation of both sample morphology and micro-sampling sites used for mass spectrometry analysis.
The technique involves extracting multiple microscale samples from precisely selected locations within a cell. These are then analyzed by electrospray ionization mass spectrometry (ESI-MS), enabling the identification of chemical species – including lipids – at subcellular resolution. The integration with an inverted fluorescence microscope allows overlay of molecular data with images of fluorescently labelled targets and morphological features.
“We have developed a new t-SPESI unit that allows us to visualize the microscopy sample in multiple modes,” commented lead author Yoichi Otsuka in a recent press release. “We can also directly observe the sampling process as the micro-samples are taken for mass spectrometry analysis.”
To demonstrate its utility, the researchers applied the system to HeLa cells and Chinese hamster ovary (CHO) cells, using fluorescence to guide sampling. Mass spectra revealed cell-type-specific lipid distributions, particularly in phosphatidylcholine (PC) species. They also evaluated the spatial distribution of lipids within individual cells, highlighting intra- and intercellular variation in lipid composition.
“When we applied our technology to model cells, we were able to observe the lipids within each individual cell using mass spectrometry imaging, directly visualize the cell by fluorescence microscopy, and also determine the surface shape of the cell,” said senior author Michisato Toyoda.
Abnormal lipid distributions are associated with a range of metabolic disorders, and the ability to correlate chemical profiles with cellular morphology and fluorescence markers could help clarify disease mechanisms in heterogeneous tissue samples. “This allows an understanding of the multidimensional molecular information of individual cells within a sample of diseased tissue,” Otsuka added.
The authors propose that t-SPESI could advance single-cell analysis by enabling direct, multimodal characterization of intracellular chemistry and morphology – a capability particularly valuable for deciphering disease heterogeneity in complex tissues.
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