This study aimed to clarify whether fullerene C60 nanoparticles induced lipid peroxidation in Cyprinus carpio brains. A stable well-characterized aqueous suspension of C60 nanoparticle (diameter: 50th and 95th percentiles, 36 and 95 nm respectively) with 0.1% Tween80 solution was prepared by bead milling. Lipid hydroperoxides (LPO) were measured in vitro in homogenized fish brain tissues containing 33 microg/mg-protein dispersed C60 nanoparticles under light and dark conditions to verify the lipid peroxidation ability of C60 and the interference of light exposure by using a commercial assay kit The LPO concentration significantly increased under the light condition but not under the dark condition. This suggests that C60 has the lipid peroxidation ability under light condition, and the light exposure that occurs during the dissection and preparation of fish brain samples containing C60 for the LPO assay interferes with the measurements of the in vivo LPO levels. Therefore, dissection and assay in the in vivo experiment were conducted under a yellow lamp or dark condition to avoid the interference of light. Moreover, the result of the in vitro test suggests that the LPO assay with irradiation might be a good method for detecting C60 in brain tissues. In the in vivo experiment, C. carpio was exposed to 4.5 mg/L nano C60 suspension for 48 h, following which the brain LPO concentration was measured. In the in vivo experiment, no fish died or exhibited abnormal symptoms during exposure. LPO assay of the C. carpio brain samples confirmed the absence of lipid peroxidation after exposure to 4.5 mg/L aqueous C60 nanoparticle suspension for 48 h. Additional LPO assay under irradiation showed that C60 did not reach the brain.

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Atomic-resolution electron microscopes utilize high-power magnetic lenses to produce magnified images of the atomic details of matter. Doing so involves placing samples inside the magnetic objective lens, where magnetic fields of up to a few tesla are always exerted. This can largely alter, or even destroy, the magnetic and physical structures of interest. Here, we describe a newly developed magnetic objective lens system that realizes a magnetic field free environment at the sample position. Combined with a higher-order aberration corrector, we achieve direct, atom-resolved imaging with sub-Å spatial resolution with a residual magnetic field of less than 0.2 mT at the sample position. This capability enables direct atom-resolved imaging of magnetic materials such as silicon steels. Removing the need to subject samples to high magnetic field environments enables a new stage in atomic resolution electron microscopy that realizes direct, atomic-level observation of samples without unwanted high magnetic field effects.