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Nanoscale fiber-optic force sensors for mechanical probing at the molecular and cellular level

Nature Protocols volume 13, pages 2714–2739 (2018)Cite this article

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Abstract

There is an ongoing need to develop ultrasensitive nanomechanical instrumentation that has high spatial and force resolution, as well as an ability to operate in various biological environments. Here, we present a compact nanofiber optic force transducer (NOFT) with sub-piconewton force sensitivity and a nanoscale footprint that paves the way to the probing of complex mechanical phenomena inside biomolecular systems. The NOFT platform comprises a SnO2 nanofiber optic equipped with a thin, compressible polymer cladding layer studded with plasmonic nanoparticles (NPs). This combination allows angstrom-level movements of the NPs to be quantified by tracking the optical scattering of the NPs as they interact with the near-field of the fiber. The distance-dependent optical signals can be converted to force once the mechanical properties of the compressible cladding are fully characterized. In this protocol, the details of the synthesis, characterization, and calibration of the NOFT system are described. The overall protocol, from the synthesis of the nanofiber optic devices to acquisition of nanomechanical data, takes ~72 h.

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Fig. 1: NOFT system overview.
Fig. 2: NOFT operation for detecting nanomechanical signals.
Fig. 3: Near-field scattering and attachment of gold nanoparticles.
Fig. 4: Structural and mechanical properties of the PEG cladding.
Fig. 5: NOFT system force response and calibration.
Fig. 6
Fig. 7
Fig. 8: Experimental setup for transferring nanofibers.
Fig. 9: Procedure for PEG coating and particle attachment.
Fig. 10: Scattering from gold NPs.
Fig. 11: Far-field imaging and data acquisition with the NOFT system.

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Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported by the National Science Foundation (ECCS 1150952) and the University of California, Office of the President (UC-LFRP 12-LR-238415). This work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of UCSD, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (grant ECCS-1542148).

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Author notes

  1. These authors contributed equally: Yuesong Shi and Beril Polat.

Authors and Affiliations

  1. Materials Science and Engineering, University of California, San Diego, San Diego, CA, USA

    Yuesong Shi & Donald J. Sirbuly

  2. Department of Nanoengineering, University of California, San Diego, San Diego, CA, USA

    Beril Polat, Qian Huang & Donald J. Sirbuly

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  1. Yuesong Shi
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  2. Beril Polat
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  4. Donald J. Sirbuly
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Contributions

Q.H. and D.J.S. conceived the project; Y.S., B.P., and Q.H. conducted the experiments and analyzed the data; and Y.S., B.P., and D.J.S. wrote the manuscript.

Corresponding author

Correspondence to Donald J. Sirbuly.

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Key references using this protocol

1. Huang, Q. et al. Nat. Photon. 11, 352–355 (2017): https://doi.org/10.1038/nphoton.2017.74

2. Ma, Y. G. et al. ACS Photonics 3, 1762–1767 (2016): https://doi.org/10.1021/acsphotonics.6b00424

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Shi, Y., Polat, B., Huang, Q. et al. Nanoscale fiber-optic force sensors for mechanical probing at the molecular and cellular level. Nat Protoc 13, 2714–2739 (2018). https://doi.org/10.1038/s41596-018-0059-9

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