title: Controlled cobalt doping in the spinel structure of magnetosome magnetite: new evidences from element- and site-specific X-ray magnetic circular dichroism analyses.
abstract: The biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science due to the precise morphology of the particles, the chain-like assembly and their unique magnetic properties. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. Despite some successful outcomes, the coordination chemistry and magnetism of such metal-doped magnetosomes still remain largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe(2+) ions by Co(2+) ions in octahedral (Oh) sites of magnetite. Both XMCD at Fe and Co L2,3 edges, and energy-dispersive X-ray spectroscopy on transmission electron microscopy analyses reveal a heterogeneous distribution of cobalt occurring either in different particles or inside individual particles. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study also demonstrates that the addition of trace cobalt in the growth medium can significantly improve both the cell growth and the magnetosome formation within M. magneticum AMB-1. Together with the cobalt occupancy within the spinel structure of magnetosomes, this study indicates that MTB may provide a promising biomimetic system for producing chains of metal-doped single-domain magnetite with an appropriate tuning of the magnetic properties for technological and biomedical applications.
authors: Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Beijing 100029, People's Republic of China France-China Biomineralization and Nano-structures Laboratory, Chinese Academy of Sciences, Beijing 100029, People's Republic of China lijinhua@mail.iggcas.ac.cn.
authors: Jinhua
authors: 0000-0003-1622-6170
authors: J
authors: Li
authors: France-China Biomineralization and Nano-structures Laboratory, Chinese Academy of Sciences, Beijing 100029, People's Republic of China IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France.
authors: Nicolas
authors: N
authors: Menguy
authors: IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France.
authors: Marie-Anne
authors: MA
authors: Arrio
authors: IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif-Sur-Yvette Cedex, France.
authors: Philippe
authors: P
authors: Sainctavit
authors: IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France.
authors: Amélie
authors: A
authors: Juhin
authors: Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Beijing 100029, People's Republic of China France-China Biomineralization and Nano-structures Laboratory, Chinese Academy of Sciences, Beijing 100029, People's Republic of China.
authors: Yinzhao
authors: Y
authors: Wang
authors: Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, People's Republic of China.
authors: Haitao
authors: H
authors: Chen
authors: IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France.
authors: Oana
authors: O
authors: Bunau
authors: Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif-Sur-Yvette Cedex, France.
authors: Edwige
authors: E
authors: Otero
authors: Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif-Sur-Yvette Cedex, France.
authors: Philippe
authors: P
authors: Ohresser
authors: Paleomagnetism and Geochronology Laboratory, Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Beijing 100029, People's Republic of China France-China Biomineralization and Nano-structures Laboratory, Chinese Academy of Sciences, Beijing 100029, People's Republic of China.
authors: Yongxin
authors: Y
authors: Pan
mesh_terms: D002942:Circular Dichroism; D003035:Cobalt / Q000378:metabolism* / Q000494:pharmacology; D052203:Ferrosoferric Oxide / Q000378:metabolism*; D055944:Magnetosomes / Q000378:metabolism*; D042201:Magnetospirillum / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D003035:Cobalt; D052203:Ferrosoferric Oxide
keywords: X-ray magnetic circular dichroism; biomineralization; cobalt-doped magnetite; coordination chemistry; magnetic alteration; magnetotactic bacteria