Depolarization signatures map gold nanorods within biological tissue

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Owing to their electromagnetic properties, tunability and biocompatibility, gold nanorods are being investigated as multifunctional probes for a range of biomedical applications. However, detection beyond the reach of traditional fluorescence and two-photon approaches and quantitation of their concentration in biological tissue remain challenging tasks in microscopy. Here, we show how the size and aspect ratio that impart gold nanorods with their plasmonic properties also make them a source of entropy. We report on how depolarization can be exploited as a strategy to visualize gold nanorod diffusion and distribution in biologically relevant scenarios ex vivo, in vitro and in vivo. We identify a deterministic relation between depolarization and nanoparticle concentration. As a result, some of the most stringent experimental conditions can be relaxed, and susceptibility to artefacts is reduced, enabling microscopic and macroscopic applications.

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Figure 1: GNR diattenuation and entropy.
Figure 2: Definitive depolarization from GNRs.
Figure 3: Depolarization characteristics of diattenuating GNRs.
Figure 4: GNR diffusion.
Figure 5: GNR transport in mouse lymphatic vessel in vivo.
Figure 6: GNR penetration and concentration in metastatic spheroids in vitro.

Change history

  • 16 August 2017

    In the version of this Article originally published online, in the inset of Fig. 2a, the small, thick black lines on the Q and U axes were not in the correct orientation. The inset has now been updated in all versions of the Article.


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This work was supported in part by National Institutes of Health (NIH) grant P41EB-015903, Koch Institute Support Grant P30-CA14051 from the National Cancer Institute (Swanson Biotechnology Center), and a Core Center Grant P30-ES002109 from the National Institute of Environmental Health Sciences. S.N.B. is a Howard Hughes Medical Institute Investigator. A.A. was supported by the Natural Sciences and Engineering Research Council of Canada and the Canadian Institutes of Health Research. T.P.P. was supported by NIH R01CA214913 and NIH R01HL128168. K.C. was supported by Burroughs Wellcome Fund Career Awards at the Scientific Interface, the Searle Scholars Program, Packard award in Science and Engineering, NARSAD Young Investigator Award, and NCSOFT Cultural Foundation.

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M.V. initiated the project. N.L., M.V., A.A., S.N.B. and B.E.B. conceived and designed the overall study. N.L. conceived, designed and performed experiments, analysed the data, carried out numerical simulations, identified the analytical model and wrote the first draft of the manuscript. N.L. and M.V. developed the simulations and built the experimental set-up. A.A. conceived the in vitro experiments, prepared the spheroids, organoids, nanoparticle aggregates and fluorescent labelled and PEGylated the nanoparticles. E.F.J.M. performed the lymph surgeries. N.L. and E.F.J.M. took the in vivo measurements. K.C. provided guidance on the in vitro organoid experiments. T.P.P. supervised the in vivo mouse experiments. S.N.B. overviewed the nanoparticle PEGylation and in vitro spheroid experiments. B.E.B. provided guidance and supervised the overall project. N.L., M.V. and B.E.B. wrote the final manuscript with contributions from all authors.

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Correspondence to Brett E. Bouma.

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The authors declare no competing financial interests.

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Lippok, N., Villiger, M., Albanese, A. et al. Depolarization signatures map gold nanorods within biological tissue. Nature Photon 11, 583–588 (2017).

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