Following iron speciation in the early stages of magnetite magnetosome biomineralization
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Teresa Perez-Gonzalez, Agata Olszewska, and Damien Faivre Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany
Tanya Prozorova) Emergent Atomic and Magnetic Structures, Division of Materials Sciences and Engineering, Ames Laboratory, Ames, Iowa 50011, USA (Received 19 July 2015; accepted 6 January 2016)
Understanding magnetosome magnetite biomineralization is of fundamental interest to devising the strategies for bioinspired synthesis of magnetic materials at the nanoscale. Thus, we investigated the early stages of magnetosome formation in this work and correlated the size and emergent crystallinity of magnetosome nanoparticles with the changes in chemical environment of iron and oxygen by utilizing advanced analytical electron microscopy techniques. We observed that magnetosomes in the early stages of biomineralization with the sizes of 5–10 nm were amorphous, with a majority of iron present as Fe31, indicative of ferric hydroxide. The magnetosomes with intermediate sizes showed partially crystalline structure with a majority of iron present as Fe31 and trace amounts of Fe21. The fully maturated magnetosomes were indexed to magnetite. Our approach provides spatially resolved structural and chemical information of individual magnetosomes with different particle sizes, attributed to magnetosomes at different stages of biomineralization.
I. INTRODUCTION
Fabrication of nanostructured magnetic materials represents one of the most promising fields of applied nanotechnology.1–4 Magnetite nanocrystals find application in many important areas of technology and nanoscience, from ferrofluidic devices,5 electromagnetic shielding,6 spintronics,7 quantum computing,8 and highdensity data storage,9 to diagnostic medicine and targeted drug delivery.10–14 While the synthetic production of monodisperse, magnetic nanocrystals with narrow size distribution at ambient temperature remains challenging, many microorganisms such as magnetotactic bacteria have found a way to master this process and biomineralize structurally perfect magnetite nanocrystals at physiological conditions.15–19 As mentioned several times in this special edition, biomineralization is the process of the production of minerals by living organisms,20,21 and magnetite can be found as biomineral precipitate in four out of the five kingdoms of living organisms (Monera, Proctista, Animalia, and Plantae).22 Magnetotactic Contributing Editor: Colin Freeman a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.33 J. Mater. Res., Vol. 31, No. 5, Mar 14, 2016
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bacteria produce intracellular nanometer-sized magnetic crystals surrounded by a phospholipid bilayer membrane, called magnetosomes, typically organized in chains.15,16,23,24 Magnetosome magnetite nanocrystals exhibit nearly perfect crystal structures with narrow size distribution and species-specific morphologies, leading to well-defined magnetic properties,
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