Solid state synthesis of carbon-encapsulated iron carbide nanoparticles and their interaction with living cells †

Superparamagnetic carbon-encapsulated iron carbide nanoparticles (NPs), Fe 7 C 3 @C, with unique properties, were produced from pure ferrocene by high pressure-high temperature synthesis. These NPs combine the merits of nanodiamonds and SPIONs but lack their shortcomings which limit their use for biomedical applications. Investigation of these NPs by X-ray diffraction, electron microscopy techniques, X-ray spectroscopic and magnetic measurement methods has demonstrated that this method of synthesis yields NPs with perfectly controllable physical properties. Using magnetic and subsequent fractional separation of magnetic NPs from residual carbon, the aqueous suspensions of Fe 7 C 3 @C NPs with an average particle size of $25 nm were prepared. The suspensions were used for in vitro studies of the interaction of Fe 7 C 3 @C NPs with cultured mammalian cells. The dynamics of interaction of the living cells with Fe 7 C 3 @C was studied by optical microscopy using time-lapse video recording and also by transmission electron microscopy. Using novel highly sensitive cytotoxicity tests based on the cell proliferation assay and long-term live cell observations it was shown that the internalization of Fe 7 C 3 @C NPs has no cytotoxic effect on cultured cells and does not interfere with the process of their mitotic division, a fundamental property that ensures the existence of living organisms. The influence of NPs on the proliferative activity of cultured cells was not detected as well. These results indicate that the carbon capsules of Fe 7 C 3 @C NPs are air-tight which could offer great opportunities for future use of these superparamagnetic NPs in biology and medicine

Magnet-Induced Behavior of Iron Carbide (Fe7C3@C) Nanoparticles in the Cytoplasm of Living Cells

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Long-term live cells observation of internalized fluorescent Fe@C nanoparticles in constant magnetic field

International audienceBackground: Theranostics application of superparamagnetic nanoparticles based on magnetite and maghemite isimpeded by their toxicity. The use of additional protective shells significantly reduced the magnetic properties of thenanoparticles. Therefore, iron carbides and pure iron nanoparticles coated with multiple layers of onion-like carbonsheath seem to be optimal for biomedicine. Fluorescent markers associated with magnetic nanoparticles provide reliablemeans for their multimodal visualization. Here, biocompatibility of iron nanoparticles coated with graphite-likeshell and labeled with Alexa 647 fluorescent marker has been investigated.Methods: Iron core nanoparticles with intact carbon shells were purified by magnetoseparation after hydrochloricacid treatment. The structure of the NPs (nanoparticles) was examined with a high resolution electron microscopy.The surface of the NPs was alkylcarboxylated and further aminated for covalent linking with Alexa Fluor 647 fluorochrometo produce modified fluorescent magnetic nanoparticles (MFMNPs). Live fluorescent imaging and correlativelight-electron microscopy were used to study the NPs intracellular distribution and the effects of constant magneticfield on internalized NPs in the cell culture were analyzed. Cell viability was assayed by measuring a proliferative poolwith Click-IT labeling.Results: The microstructure and magnetic properties of superparamagnetic Fe@C core–shell NPs as well as theirendocytosis by living tumor cells, and behavior inside the cells in constant magnetic field (150 mT) were studied.Correlative light-electron microscopy demonstrated that NPs retained their microstructure after internalization bythe living cells. Application of constant magnetic field caused orientation of internalized NPs along power lines thusdemonstrating their magnetocontrollability. Carbon onion-like shells make these NPs biocompatible and enablelong-term observation with confocal microscope. It was found that iron core of NPs shows no toxic effect on the cellphysiology, does not inhibit the cell proliferation and also does not induce apoptosis.Conclusions: Non-toxic, biologically compatible superparamagnetic fluorescent MFMNPs can be further used forbiological application such as delivery of biologically active compounds both inside the cell and inside the wholeorganism, magnetic separation, and magnetic resonance imaging (MRI) diagnostics

Solid State Synthesis of Carbon-Encapsulated Iron Carbide Nanoparticles and Their Interaction with Living Cells

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Bifunctional Magnetite–Gold Nanoparticles for Magneto-Mechanical Actuation and Cancer Cell Destruction

International audienceMagnetite–gold dumbbell nanoparticles are essential for biomedical applications due to the presence of two surfaces with different chemical natures and the potential combination of magnetic and plasmonic properties. Here, the remote actuation of Fe3O4-Au hybrid particles in a rotating (1 Hz, 7 mT), static (7 mT) or pulsed low-frequency (31 Hz, 175 mT, 30 s pulse/30 s pause) magnetic field was studied. The particles were synthesized by a high-temperature wet chemistry protocol and exhibited superparamagnetic properties with the saturation magnetization of 67.9 ± 3.0 Am2 kg−1. We showcased the nanoparticles’ controlled aggregation in chains (rotating/static magnetic field) in an aqueous solution and their disaggregation when the field was removed. The investigation of nanoparticle uptake by LNCaP and PC-3 cancer cells demonstrated that Fe3O4-Au hybrids mainly escaped endosomes and accumulated in the cytoplasm. A significant fraction of them still responded to a rotating magnetic field, forming short chains. The particles were not toxic to cells at concentrations up to 210 μg (Fe3O4) mL−1. However, cell viability decrease after incubation with the nanoparticles (≥70 μg mL−1) and exposure to a pulsed low-frequency magnetic field was found. We ascribe this effect to mechanically induced cell destruction. Overall, this makes Fe3O4-Au nanostructures promising candidates for intracellular actuation for future magneto-mechanical cancer therapies.</jats:p

Magnetocontrollability of Fe7C3@C superparamagnetic nanoparticles in living cells

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Bifunctional Magnetite&ndash;Gold Nanoparticles for Magneto-Mechanical Actuation and Cancer Cell Destruction

Magnetite&ndash;gold dumbbell nanoparticles are essential for biomedical applications due to the presence of two surfaces with different chemical natures and the potential combination of magnetic and plasmonic properties. Here, the remote actuation of Fe3O4-Au hybrid particles in a rotating (1 Hz, 7 mT), static (7 mT) or pulsed low-frequency (31 Hz, 175 mT, 30 s pulse/30 s pause) magnetic field was studied. The particles were synthesized by a high-temperature wet chemistry protocol and exhibited superparamagnetic properties with the saturation magnetization of 67.9 &plusmn; 3.0 Am2 kg&minus;1. We showcased the nanoparticles&rsquo; controlled aggregation in chains (rotating/static magnetic field) in an aqueous solution and their disaggregation when the field was removed. The investigation of nanoparticle uptake by LNCaP and PC-3 cancer cells demonstrated that Fe3O4-Au hybrids mainly escaped endosomes and accumulated in the cytoplasm. A significant fraction of them still responded to a rotating magnetic field, forming short chains. The particles were not toxic to cells at concentrations up to 210 &mu;g (Fe3O4) mL&minus;1. However, cell viability decrease after incubation with the nanoparticles (&ge;70 &mu;g mL&minus;1) and exposure to a pulsed low-frequency magnetic field was found. We ascribe this effect to mechanically induced cell destruction. Overall, this makes Fe3O4-Au nanostructures promising candidates for intracellular actuation for future magneto-mechanical cancer therapies

Bifunctional Magnetite–Gold Nanoparticles for Magneto-Mechanical Actuation and Cancer Cell Destruction

Magnetite–gold dumbbell nanoparticles are essential for biomedical applications due to the presence of two surfaces with different chemical natures and the potential combination of magnetic and plasmonic properties. Here, the remote actuation of Fe3O4-Au hybrid particles in a rotating (1 Hz, 7 mT), static (7 mT) or pulsed low-frequency (31 Hz, 175 mT, 30 s pulse/30 s pause) magnetic field was studied. The particles were synthesized by a high-temperature wet chemistry protocol and exhibited superparamagnetic properties with the saturation magnetization of 67.9 ± 3.0 Am2 kg−1. We showcased the nanoparticles’ controlled aggregation in chains (rotating/static magnetic field) in an aqueous solution and their disaggregation when the field was removed. The investigation of nanoparticle uptake by LNCaP and PC-3 cancer cells demonstrated that Fe3O4-Au hybrids mainly escaped endosomes and accumulated in the cytoplasm. A significant fraction of them still responded to a rotating magnetic field, forming short chains. The particles were not toxic to cells at concentrations up to 210 μg (Fe3O4) mL−1. However, cell viability decrease after incubation with the nanoparticles (≥70 μg mL−1) and exposure to a pulsed low-frequency magnetic field was found. We ascribe this effect to mechanically induced cell destruction. Overall, this makes Fe3O4-Au nanostructures promising candidates for intracellular actuation for future magneto-mechanical cancer therapies