Letter

Inertial picobalance reveals fast mass fluctuations in mammalian cells

Received:
Accepted:
Published online:

Abstract

The regulation of size, volume and mass in living cells is physiologically important, and dysregulation of these parameters gives rise to many diseases1. Cell mass is largely determined by the amount of water, proteins, lipids, carbohydrates and nucleic acids present in a cell, and is tightly linked to metabolism, proliferation2 and gene expression3. Technologies have emerged in recent years that make it possible to track the masses of single suspended cells4,5 and adherent cells6,7,8. However, it has not been possible to track individual adherent cells in physiological conditions at the mass and time resolutions required to observe fast cellular dynamics. Here we introduce a cell balance (a ‘picobalance’), based on an optically excited microresonator, that measures the total mass of single or multiple adherent cells in culture conditions over days with millisecond time resolution and picogram mass sensitivity. Using our technique, we observe that the mass of living mammalian cells fluctuates intrinsically by around one to four per cent over timescales of seconds throughout the cell cycle. Perturbation experiments link these mass fluctuations to the basic cellular processes of ATP synthesis and water transport. Furthermore, we show that growth and cell cycle progression are arrested in cells infected with vaccinia virus, but mass fluctuations continue until cell death. Our measurements suggest that all living cells show fast and subtle mass fluctuations throughout the cell cycle. As our cell balance is easy to handle and compatible with fluorescence microscopy, we anticipate that our approach will contribute to the understanding of cell mass regulation in various cell states and across timescales, which is important in areas including physiology, cancer research, stem-cell differentiation and drug discovery.

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Acknowledgements

We thank H.-P. Lang, F. Huber, W. Junge, E. Meyer, T. Glatzel and J. Adams for discussion; E. Meyer, T. Glatzel and A. Tonin for help with the beam deflection diagram; the mechanical and electronic workshops of the Physics Department of University Basel, P. Buchmann and P. Argast for help with building our device; A. Ponti for technical support with Imaris 8.1 to determine cell position; D. Mathys for assisting with electron microscopy and focused ion beam lithography; T. Lopez and V. Jäggin for assistance with FACS operation; and Newport Corporation, Attocube Systems AG, Nanonis (SPECS Zurich GmbH), Carl Zeiss AG and Nanosurf AG for technical support. This work was funded by the Swiss Commission for Technology and Innovation (CTI; grant 17970.1 PFNM-NM to D.J.M.), the European Molecular Biology Organization (EMBO; ALTF 506-2012 to D.M.-M. and ALTF 424-2016 to B.G.), the Swiss Nanoscience Institute Basel and the NCCR Molecular Systems Engineering. C.B. and J.M. are supported by core funding to the MRC Laboratory for Molecular Cell Biology, University College London.

Author information

Author notes

    • David Martínez-Martín
    •  & Gotthold Fläschner

    These authors contributed equally to this work.

Affiliations

  1. Eidgenössische Technische Hochschule (ETH) Zürich, Department of Biosystems Science and Engineering, 4058 Basel, Switzerland.

    • David Martínez-Martín
    • , Gotthold Fläschner
    • , Benjamin Gaub
    • , Richard Newton
    •  & Daniel J. Müller
  2. Swiss Nanoscience Institute (SNI), University of Basel, 4056 Basel, Switzerland.

    • Sascha Martin
    •  & Christoph Gerber
  3. MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK.

    • Corina Beerli
    •  & Jason Mercer

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Contributions

D.M.-M., G.F., C.G. and D.J.M. designed the experiments. D.M.-M., C.G., S.M. and D.J.M. designed and built the cell balance. R.N. generated the fibroblast cell line stably expressing H2B–eGFP and mCherry–actin. D.M.-M. and G.F. set up the controlled environmental system and conducted all experiments. B.G. performed parts of the VACV experiments. D.M.-M., G.F., C.G. and D.J.M. analysed the data. C.B. and J.M. constructed, produced and purified the VACV and provided the HeLa (ATCC CCL-2) and BSC40 (ATCC CRL-2761) cell lines. D.M.-M., G.F., B.G., R.N., J.M., C.G. and D.J.M. wrote the manuscript. All authors discussed the experiments, read and approved the manuscript.

Competing interests

D.M.-M., S.M., C.G. and D.J.M. applied for two patents related to the cell balance device compatible with optical microscopy (WO/2015/120,991 and WO/2015/120,992). D.M.-M., G.F., S.M. and D.J.M. applied for a patent for the controlled environmental system enabling cell mass measurements and optical microscopy under cell culture conditions (WO/2017/012708). D.M.-M., G.F. and D.J.M. applied for a patent for microcantilevers to measure the mass of a cell independently of its positional changes (EP17001238).

Corresponding authors

Correspondence to David Martínez-Martín or Daniel J. Müller.

Reviewer Information Nature thanks Y. Dufrene, G. Wuite and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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