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Intracellular speciation of gold nanorods alters the conformational dynamics of genomic DNA

Abstract

Gold nanorods are one of the most widely explored inorganic materials in nanomedicine for diagnostics, therapeutics and sensing1. It has been shown that gold nanorods are not cytotoxic and localize within cytoplasmic vesicles following endocytosis, with no nuclear localization2,3, but other studies have reported alterations in gene expression profiles in cells following exposure to gold nanorods, via unknown mechanisms4. In this work we describe a pathway that can contribute to this phenomenon. By mapping the intracellular chemical speciation process of gold nanorods, we show that the commonly used Au–thiol conjugation, which is important for maintaining the noble (inert) properties of gold nanostructures, is altered following endocytosis, resulting in the formation of Au(i)–thiolates that localize in the nucleus5. Furthermore, we show that nuclear localization of the gold species perturbs the dynamic microenvironment within the nucleus and triggers alteration of gene expression in human cells. We demonstrate this using quantitative visualization of ubiquitous DNA G-quadruplex structures, which are sensitive to ionic imbalances, as an indicator of the formation of structural alterations in genomic DNA.

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Fig. 1: Thiol-functionalized gold nanorods are non-toxic and are localized in intracellular vesicles following endocytosis.
Fig. 2: Alterations in G4-DNA formation in the genome, observed following gold nanorod internalization in cells.
Fig. 3: Intracellular chemical speciation of thiol-functionalized gold nanorods.
Fig. 4: Alterations in gene expression associated with changes in G4 formation and gold nanorod internalization.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

The authors thank S. Balasubramanian for his gift of pSANG10-3F-BG4. This research was supported by the Australian Research Council, the National Health and Medical Research Council and the Raine Medical Research Foundation for the Healy Research Collaboration Award. The authors acknowledge the facilities and the scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, a facility funded by the University, State and Commonwealth Governments, as well as the WA X-ray Surface Analysis Facility of the John de Laeter Centre, funded by the Australian Research Council LIEF grant LE120100026. J.A.Kr. acknowledges Cancer Council Western Australia for a PhD Top Up scholarship.

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N.M.S. and K.S.I. developed the hypothesis. D.H., J.A.Ke. and K.S.I designed the GNR intracellular evaluation experiments. N.M.S., L.H.H., J.A.Kr., D.H. and R.C. designed the G4 interaction experiments. C.W.E., D.H. and J.A.Kr. performed the cell viability and toxicity analysis. M.No. performed the MTAB synthesis. N.M.S., M.Ng., A.L.K., A.J.B. and C.S.B. carried out BG4 antibody production and purification. T.D.C., J.A.Kr. and J.-P.V. performed the XPS experiments. D.H., J.A.Kr., P.G., H.J. and M.R.K. performed the NanoSIMS experiments. D.H. and P.T. performed the qPCR experiments. A.M.M., M.S. and D.H. performed the nanoparticle synthesis and characterization. J.A.Kr. and C.W.E. performed ICP experiments. M.A. and M.F. performed TEM/NanoSIMS sample preparation and analysis. All authors contributed to writing the manuscript.

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Correspondence to Nicole M. Smith or K. Swaminathan Iyer.

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Ho, D., Kretzmann, J.A., Norret, M. et al. Intracellular speciation of gold nanorods alters the conformational dynamics of genomic DNA. Nature Nanotech 13, 1148–1153 (2018). https://doi.org/10.1038/s41565-018-0272-2

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