Image Credit: TOFWERK
This article focuses on the single cell ICP-MS and proves the efficacy of icpTOF technology for investigating the cell ionome on an individual cell basis with no prior understanding of the elemental composition of the cell.
Metals and non-metals such as P, S, K, Na, Mg, Ca, Fe, Mn, Zn, Cu, and Se are the fundamental building blocks of a living cell. Included in the structure of proteins or as free ions, they manage the essential functions of a cell.
For example, sulfur assists in the connection of various proteins; phosphorus is available as phosphate in GTP, ATP, RNA, and DNA, while chlorine, potassium, calcium, and sodium are critical for the generation of electrical signals by nerve cells.
Alternative trace metals are also necessary for proteins and enzymes so that they can carry out chemical reactions.
Traditional Cell Ionomics
The distribution of elements in cells, also called the cell ionome1, can be utilized to establish the state of development and growth rate of cells.
Variations in elemental composition can be used to investigate the reaction to toxic drugs or compounds such as Pt-based compounds employed in the treatment of cancer.
Cell ionomic studies conventionally utilize ICP-MS after the acid digestion of a cell pellet. This process normally requires a comparatively large amount of cells, increasing the cost of analysis, and offers only the average results for a particular population of cells.
Within the cell population, the heterogeneity is not considered and any data on cell-to-cell variability is missed.
Figure 1. Example of a recorded signal for a single Wickerhamomyces anomalus yeast cell. Data were acquired with an integration time of 120 µs. Image Credit: TOFWERK
Every cell is distinctive and evaluating single cells provides the latest insights into cell-environment interactions and intracellular biochemistry.
As several processes in a biological system are interrelated, the ability to access every element within the cell maximizes the efficiency and power of the study, resulting in optimized predictions and models.
The TOFWERK icpTOF mass spectrometer provides the simultaneous identification of each element within a single cell2, which positions it as an exemplary and exclusive tool for multi-parametric ionomics.
Figure 2. Left: Fractional mean counts of different elements in single cells (defined as counts of element X/Sum of counts of all elements). Right: Mean counts of different elements in single cells from different cell species. The difference in mean and fractional counts indicate the difference in element concentrations between different cell species. Image Credit: TOFWERK
Figure 3. PCA plot for different species. The analysis shows no clear separation of cell populations from different species. There was just a minor diﬀerence between S. cerevisiae and S. pombe and S. pombe and W. anomalus detected. Image Credit: TOFWERK
Single Cell ICP-MS Analysis Results
In this investigation, the cell ionome of various yeast cell species grown in Synthetic Complete Glucose Broth media spiked with Ni, Cd, and Co were analyzed.
A traditional sample introduction system was included with the icpTOF R and was run at an acquisition rate of 8250 spectra/s in triggered mode (120 µs integration time) or 550 spectra/s in continuous mode (1.8 ms integration time).
The signals of single cells were divided from the ionic background, employing the Particle Processing Module in TOFWERK’s TofPilot software.
Mg, Zn, and P were identified in each of the cells and Fe, Mn, Cd, and K were identified in some of the cells, which were likely to be bigger.
Only the data of Mg, Zn, and P were investigated. A significant difference in the relative and average concentrations of various elements in a range of species was noted (Figure 2).
Due to the results of Principal Component Analysis (PCA), it was concluded that it was impossible to divide cells from various species completely. There was only a small diﬀerence between S. pombe and S. cerevisiae and W. anomalus and S. pombe.
This investigation displays the effectiveness of the icpTOF technology for analyzing the cell ionome on an individual cell basis with no previous knowledge of the elemental composition of the cell.
References and Further Reading
- Malinouski, M.; Hasan, N. M.; Zhang, Y.; Seravalli, J.; Lin, J.; Avanesov, A.; Lutsenko, S.; Gladyshev, V. N., Genome-wide RNAi ionomics screen reveals new genes and regulation of human trace element metabolism. Nature Communications 2014, 5, 3301.
- Hendriks, L.; Gundlach-Graham, A.; Hattendorf, B.; Günther, D., Characterization of a new ICP-TOFMS instrument with continuous and discrete introduction of solutions. J. Anal. At. Spectrom. 2017, 32 (3), 548-561.
Produced from materials originally authored by Olga Borovinskaya from TOFWERK, Thun, Switzerland, and Simran Aulakh and Markus Ralser from The Francis Crick Institute.
TOFWERK is a global leader in time-of-flight mass spectrometry, delivering sensitive instruments for laboratory, industrial, and field analyses. Our customers’ interests range from materials science and geochemistry to metabolomics and trace-gas
TOFWERK engineers and scientists collaborate with research laboratories and OEM customers to develop custom MS solutions based on our modular design platform. This platform enables rapid design and manufacturing of novel instrumentation for research laboratories and OEM customers.
Our end-user product line includes the icpTOF, Vocus PTR-TOF, IMS-TOF, and EI-TOF for GC. These mass spectrometers bring the speed and sensitivity of TOFMS to many disciplines and sample types.
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