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Optical magnetic imaging of living cells

2013; Nature Portfolio; Volume: 496; Issue: 7446 Linguagem: Inglês

10.1038/nature12072

1476-4687

D. Le Sage, Keigo Arai, David R. Glenn, Stephen J. DeVience, Linh Pham, Lilah Rahn-Lee, Mikhail D. Lukin, Amir Yacoby, Arash Komeili, Ronald L. Walsworth,

Characterization and Applications of Magnetic Nanoparticles

A diamond chip with nitrogen–vacancy centres is used for magnetic imaging of living magnetotactic bacteria with sub-cellular spatial resolution. In recent years, the nitrogen–vacancy (NV) colour centres found in diamond have been shown to be excellent high-precision probes of magnetic structures down to single spins. They also offer the unique capability of high-resolution magnetic imaging at ambient conditions, so could potentially be used to study the magnetic properties of living biological specimens. Ronald Walsworth and colleagues now use a diamond chip with NV centres to obtain images of living magnetotactic bacteria under ambient laboratory conditions with sub-cellular (400 nm) spatial resolution. They reconstruct the magnetic field created by chains of magnetic nanoparticles (magnetosomes) produced in the bacteria. The work presents a new capability for bioimaging of magnetic structures, and could be used to look at magnetic nanoparticle formation in organisms in which it has been proposed as a mechanism for magnetic navigation. Magnetic imaging is a powerful tool for probing biological and physical systems. However, existing techniques either have poor spatial resolution compared to optical microscopy and are hence not generally applicable to imaging of sub-cellular structure (for example, magnetic resonance imaging1), or entail operating conditions that preclude application to living biological samples while providing submicrometre resolution (for example, scanning superconducting quantum interference device microscopy2, electron holography3 and magnetic resonance force microscopy4). Here we demonstrate magnetic imaging of living cells (magnetotactic bacteria) under ambient laboratory conditions and with sub-cellular spatial resolution (400 nanometres), using an optically detected magnetic field imaging array consisting of a nanometre-scale layer of nitrogen–vacancy colour centres implanted at the surface of a diamond chip. With the bacteria placed on the diamond surface, we optically probe the nitrogen–vacancy quantum spin states and rapidly reconstruct images of the vector components of the magnetic field created by chains of magnetic nanoparticles (magnetosomes) produced in the bacteria. We also spatially correlate these magnetic field maps with optical images acquired in the same apparatus. Wide-field microscopy allows parallel optical and magnetic imaging of multiple cells in a population with submicrometre resolution and a field of view in excess of 100 micrometres. Scanning electron microscope images of the bacteria confirm that the correlated optical and magnetic images can be used to locate and characterize the magnetosomes in each bacterium. Our results provide a new capability for imaging bio-magnetic structures in living cells under ambient conditions with high spatial resolution, and will enable the mapping of a wide range of magnetic signals within cells and cellular networks5,6.