Abstract
Magnetotactic bacteria biomineralize iron into magnetite (Fe3O4) nanoparticles that are surrounded by lipid vesicles. These ‘magnetosomes’ have considerable potential for use in bio- and nanotechnological applications because of their narrow size and shape distribution and inherent biocompatibility1,2,3. The ability to tailor the magnetic properties of magnetosomes by chemical doping would greatly expand these applications4,5; however, the controlled doping of magnetosomes has so far not been achieved. Here, we report controlled in vivo cobalt doping of magnetosomes in three strains of the bacterium Magnetospirillum. The presence of cobalt increases the coercive field of the magnetosomes—that is, the field necessary to reverse their magnetization—by 36–45%, depending on the strain and the cobalt content. With elemental analysis, X-ray absorption and magnetic circular dichroism, we estimate the cobalt content to be between 0.2 and 1.4%. These findings provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties.
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Acknowledgements
This work was supported by the Engineering and Physical Sciences Research Council (Grant no. EP/C53204X/1 & EP/D057310/1). We would like to thank L. Eades for technical support with ICP-OES, as well as C. How, M. Tanaka and M. Jaffer for support with TEM. We thank A. Muxworthy for assistance and discussions regarding the computational data and V. S. Coker for useful discussions and advice about the XMCD data. We are also grateful to the staff of the Daresbury Laboratory for their support during our experiment there.
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S.S.S. and A.H. conceived the idea for the study. S.S.S., A.H. and F.B.W. designed the study. S.S.S. and F.B.W. optimized the bacterial growth; S.S.S. performed the bacterial preparations, magnetosome extractions, TEM, magnetic and ICP-OES experiments and analysis. N.D.T., G.v.d.L., A.H. and S.S.S. designed the XMCD study and S.S.S., F.B.W and N.D.T. performed the XMCD experiment. N.D.T and G.v.d.L. analysed the XMCD data and produced Fig. 2. W.W. performed all the computational calculation and analysis. S.S.S. composed the manuscript with contributions from all the authors. All the authors discussed the results and commented on the manuscript.
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Staniland, S., Williams, W., Telling, N. et al. Controlled cobalt doping of magnetosomes in vivo. Nature Nanotech 3, 158–162 (2008). https://doi.org/10.1038/nnano.2008.35
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DOI: https://doi.org/10.1038/nnano.2008.35
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