Publisher's Note: “Two-component magnetic structure of iron oxide nanoparticles mineralized in Listeria innocua protein cages” [J. Appl. Phys. 107, 114703 (2010)] (original) (raw)
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Journal of Applied Physics, 2010
Magnetometry was used to determine the magnetic properties of maghemite ͑␥-Fe 2 O 3 ͒ nanoparticles formed within Listeria innocua protein cage. The electron magnetic resonance spectrum shows the presence of at least two magnetization components. The magnetization curves are explained by a sum of two Langevin functions in which each filled protein cage contains both a large magnetic iron oxide core plus an amorphous surface consisting of small noncoupled iron oxide spin clusters. This model qualitatively explains the observed decrease in the temperature dependent saturation moment and removes an unrealistic temperature dependent increase in the particle moment often observed in nanoparticle magnetization measurements.
Magnetic properties of Co3O4 nanoparticles mineralized in Listeria innocua Dps
Journal of Applied Physics, 2006
Temperature-dependent magnetic measurements are reported for 4.34 nm antiferromagnetic Co 3 O 4 nanoparticles mineralized in the Listeria innocua Dps protein cage. ac measurements show a superparamagnetic blocking temperature of roughly 5.4 K and give an extracted anisotropy energy density of ͑7.6± 0.4͒ ϫ 10 4 J/m 3. The Néel temperature for the Co 3 O 4 nanoparticles, determined with dc magnetometry, was determined to be roughly 15± 2 K.
Functionalization of magnetite nanoparticles for protein immobilization
2007
In the present study, a new magnetic powder based on magnetite can be used as a petroleum crude oil collector. Amidoximes based on rosin as a natural product can be prepared from a reaction between hydroxylamine and rosin/acrylonitrile adducts. The produced rosin amidoximes were used as capping agents for magnetite nanoparticles to prepare hydrophobic coated magnetic powders. A new class of monodisperse hydrophobic magnetite nanoparticles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The structure and morphology of magnetite capped with rosin amidoxime were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The magnetic properties were determined from vibrating sample magnetometer (VSM) analyses. These prepared magnetite nanoparticles were tested as bioactive nanosystems and their antimicrobial effects were investigated. The prepared nanomaterials were examined as a crude oil collector using magnetic fields. The results show promising data for the separation of the petroleum crude oil from aqueous solution in environmental pollution cleanup.
Magnetic Properties and Biological Activity Evaluation of Iron Oxide Nanoparticles
Journal of Nanomaterials, 2013
The aim of this study was to provide information about the biological properties of iron oxide nanoparticles (IO-NPs) obtained in an aqueous suspension. The IO-NPs were characterized by transmission electron microscopy (TEM). Analysis of hysteresis loops data at room temperature for magnetic IO-NPs sample indicated that the IO-NPs were superparamagnetic at room temperature. The calculated saturation magnetization for magnetic iron oxide was M s = 18.1 emu/g. The antimicrobial activity of the obtained PMC-NPs was tested against Gram-negative (Pseudomonas aeruginosa 1397, Escherichia coli ATCC 25922), Gram-positive (Enterococcus faecalis ATCC 29212, Bacillus subtilis IC 12488) bacterial as well as fungal (Candida krusei 963) strains. The obtained results suggested that the antimicrobial activity of IO-NPs is dependent on the metallic ions concentrations and on the microbial growth state, either planktonic or adherent. The obtained IO-NPs exhibited no cytotoxic effect on HeLa cells at the active antimicrobial concentrations.
Electron magnetic resonance of iron oxide nanoparticles mineralized in protein cages
Journal of Applied Physics, 2005
Magnetic and structural properties determined by electron magnetic resonance ͑EMR͒ spectroscopy are reported for maghemite ͑␥-Fe 2 O 3 ͒ nanoparticles formed through template-constrained mineralization within three protein cages with nominal diameters of 5, 8, and 24 nm. EMR spectra, obtained at 4.0, 9.2, 34.6, 94.9, and 130.0 GHz, and at ambient temperature, show dramatic frequency dependent effects in the line shapes, line-widths, and resonance-field shifts. Simulations of the spectra are used to obtain moment distribution parameters, which are consistent with size limitations imposed by the protein cages, but which reflect significant departures from bulk magnetization properties.
Magnetic properties of bacterial magnetosomes and chemosynthesized magnetite nanoparticles
In this work, the magnetic properties of biologically produced magnetite (magnetosomes) by a mineralization process of magnetotactic bacteria {Magnetospirillum sp.} AMB-1 were compared to those of chemically synthesized magnetite nanoparticles and nanorods. X-ray diffraction data reveal that for all samples the peaks come from magnetite. A sharp magnetic transition (Verwey transition) is clearly observed in magnetosomes at 105 K (magnetite nanocrystals obtained by mineralization) and nanorodes at 112 K, in opposite, this transition is significantly smeared in Fe_{3}O_{4} powder, where the magnetic nanoparticles are separated and the magnetic fluctuations are strong to overcome magnetic anisotropy and randomize magnetic moment. The existence of coercivity of 71 Oe at room temperature is related to the fact that the mean diameter (34 nm) is larger than the critical size for the transition from superparamagnetic to ferromagnetic behaviour. Figs 6, Refs 14.
Rasayan Journal of chemistry, 2020
In the present paper the synthesis of magnetite nanoparticles and their surface functionalization with protein has been described. Surface functionalization of these nanoparticles was confirmed using various techniques including Transmission Electron Microscopy, X-Ray Diffraction, Vibrating Scanning Magnetometry, Thermo-gravimetric studies and Fourier Transform Infrared Spectroscopy. Further, surface-functionalized magnetite nanoparticles were loaded with ciprofloxacin drug and then screened for their antibacterial activity against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains.
Effects of Modified Magnetite Nanoparticles on Bacterial Cells and Enzyme Reactions
Nanomaterials
Current paper presents biological effects of magnetite nanoparticles (MNPs). Relations of MNP’ characteristics (zeta-potential and hydrodynamic diameters) with effects on bacteria and their enzymatic reactions were the main focus. Photobacterium phosphoreum and bacterial enzymatic reactions were chosen as bioassays. Three types of MNPs were under study: bare Fe3O4, Fe3O4 modified with 3-aminopropyltriethoxysilane (Fe3O4/APTES), and humic acids (Fe3O4/HA). Effects of the MNPs were studied at a low concentration range (< 2 mg/L) and attributed to availability and oxidative activity of Fe3+, high negative surface charge, and low hydrodynamic diameter of Fe3O4/HA, as well as higher Fe3+ content in suspensions of Fe3O4/HA. Low-concentration suspensions of bare Fe3O4 provided inhibitory effects in both bacterial and enzymatic bioassays, whereas the MNPs with modified surface (Fe3O4/APTES and Fe3O4/HA) did not affect the enzymatic activity. Under oxidative stress (i.e., in the solutions...