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Nanomaterials for in vivo imaging of mechanical forces and electrical fields

Abstract

Cellular signalling is governed in large part by mechanical forces and electromagnetic fields. Mechanical forces play a critical role in cell differentiation, tissue organization and diseases such as cancer and heart disease; electrical fields are essential for intercellular communication, muscle contraction, neural signalling and sensory perception. Therefore, quantifying a biological system's forces and fields is crucial for understanding physiology and disease pathology and for developing medical tools for repair and recovery. This Review highlights advances in sensing mechanical forces and electrical fields in vivo, focusing on optical probes. The emergence of biocompatible optical probes, such as genetically encoded voltage indicators, molecular rotors, fluorescent dyes, semiconducting nanoparticles, plasmonic nanoparticles and lanthanide-doped upconverting nanoparticles, offers exciting opportunities to push the limits of spatial and temporal resolution, stability, multi-modality and stimuli sensitivity in bioimaging. We further discuss the materials design principles behind these probes and compare them across various metrics to facilitate sensor selection. Finally, we examine which advances are necessary to fully unravel the role of mechanical forces and electrical fields in vivo, such as the ability to probe the vectorial nature of forces, the development of combined force and field sensors, and the design of efficient optical actuators.

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Figure 1: Mechanical forces and electric fields in biology.
Figure 2: Comparison of mechanical force probes.
Figure 3: Mechanical force sensors.
Figure 4: Measuring electrical fields.
Figure 5: Electrical field sensors.

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Acknowledgements

The authors acknowledge financial support from Stanford NeuroFab and Bio-X Interdisciplinary Initiatives Committee (IIP). R.K. was supported by an Eastman Kodak fellowship. A.L. was supported by the NSF GRFP (2013156180).

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Mehlenbacher, R., Kolbl, R., Lay, A. et al. Nanomaterials for in vivo imaging of mechanical forces and electrical fields. Nat Rev Mater 3, 17080 (2018). https://doi.org/10.1038/natrevmats.2017.80

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