Bare Iron Oxide Nanoparticles Research Articles

Functionalization of strongly interacting magnetic nanocubes with (thermo)responsive coating and their application in hyperthermia and heat-triggered drug delivery.

Herein, we prepare nanohybrids by incorporating iron oxide nanocubes (cubic-IONPs) within a thermoresponsive polymer shell that can act as drug carriers for doxorubicin(doxo). The cubic-shaped nanoparticles employed are at the interface between superparamagnetic and ferromagnetic behavior and have an exceptionally high specific absorption rate (SAR), but their functionalization is extremely challenging compared to bare superparamagnetic iron oxide nanoparticles as they strongly interact with each other. By conducting the polymer grafting reaction using reversible addition-fragmentation chain transfer (RAFT) polymerization in a viscous solvent medium, we have here developed a facile approach to decorate the nanocubes with stimuli-responsive polymers. When the thermoresponsive shell is composed of poly(N-isopropylacrylamide-co-polyethylene glycolmethyl ether acrylate), nanohybrids have a phase transition temperature, the lower critical solution temperature (LCST), above 37 °C in physiological conditions. Doxo loaded nanohybrids exhibited a negligible drug release below 37 °C but showed a consistent release of their cargo on demand by exploiting the capability of the nanocubes to generate heat under an alternating magnetic field (AMF). Moreover, the drug free nanocarrier does not exhibit cytotoxicity even when administered at high concentration of nanocubes (1g/L of iron) and internalized at high extent (260 pg of iron per cell). We have also implemented the synthesis protocol to decorate the surface of nanocubes with poly(vinylpyridine) polymer and thus prepare pH-responsive shell coated nanocubes.

In vitro toxicity assessment of chitosan oligosaccharide coated iron oxide nanoparticles

Iron oxide nanoparticles (INPs) have potential biological, biomedical and environmental applications. These applications require surface modification of the iron oxide nanoparticles, which makes it non-toxic, biocompatible, stable and non-agglomerative in natural and biological surroundings. In the present study, iron oxide nanoparticles (INPs) and chitosan oligosaccharide coated iron oxide nanoparticles (CSO-INPs) were synthesized to evaluate the effect of surface coating on the stability and toxicity of nanoparticles. Comparative in vitro cytotoxicity of nanoparticles was evaluated in HeLa (human cervix carcinoma), A549 (human lung carcinoma) and Hek293 (human embryonic kidney) cells by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay along with flow cytometry study for cell viability, membrane integrity, mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) production. Morphological alteration in nanoparticles treated cells was analyzed by Acridine orange/ethidium bromide double staining and electron microscopy. Synthesized nanoparticles were found to be spherical in shape, well dispersed and stable at various pH values, making them suitable for biomedical and environmental applications. The present study also indicates that the chitosan oligosaccharide coating on iron oxide nanoparticles results in the decrease in cellular damage and moderate ROS production, thereby, significantly decreasing the cytotoxic impact of bare iron oxide nanoparticles.

SPION-mediated soil DNA extraction and comparative analysis with conventional and commercial kit-based protocol

Direct isolation of soil DNA comes as an emerging technology to understand the microbial diversity of a particular environment circumventing the dependency on culturable methods. Soil DNA isolation is tough due to the presence of various organic components present in soil which interfere in extraction procedure. Here, we report a novel direct soil DNA extraction protocol utilizing bare superparamagnetic iron oxide nanoparticles and its comparison with conventional and commercial kit-based soil DNA extraction methods. The quality, quantity and feasibility of the recovered DNA from all the three methods towards various molecular techniques were checked. Our magnetic nanoparticle-based soil DNA extraction successfully yields pure DNA without any RNA or protein contamination as revealed by the nanodrop spectrophotometer and agarose gel electrophoretic study. Different methods of soil DNA extraction were evaluated on the basis of PCR, denaturing gradient gel electrophoresis and real-time PCR. Soil DNA extracted using conventional method fails to carry out critical molecular biology techniques where as magnetic nanoparticle-based soil DNA extraction gave good results which is comparable to commercial kit. This comparative study suggests that protocol described in this report is novel, less time consuming, cost effective with fewer handling steps and yields high quantity, good quality DNA from soil.

English

Iron oxide nanoparticles were synthesized by co-precipitation method. The polyunsaturated carrier oil (flaxseed oil) is used as a stabilizing agent for iron oxide nanoparticles. Kirby Bauer method was used to investigate the antibiotic sensitivity of carrier oil stabilized and uncoated SPIONs at 10 and 20 μg/L on Gram-positive bacterium Bacillus cereus (vegetative cell). The nanoparticles were characterized by X-ray diffraction method (XRD), Fourier transform infrared red (FTIR) analysis, particle size analyzer and Transmission Electron Microscopy. Structure of magnetite nanoparticles was confirmed by XRD analysis and the estimation of nanoparticle size was confirmed with TEM. The attachment of functional groups of oil was predicted using FTIR spectroscopy. This comparison study revealed that carrier oils stabilized iron oxide nanoparticles show more antibacterial activity than the bare iron oxide nanoparticles.   Key words: Iron oxide nanoparticles, flaxseed oil, Bacillus cereus

Maghemite Nanoparticles on Electrospun CNFs Template as Prospective Lithium-Ion Battery Anode

In this work, maghemite (γ-Fe2O3) nanoparticles were uniformly coated on carbon nanofibers (CNFs) by a hybrid synthesis procedure combining an electrospinning technique and hydrothermal method. Polyacrylonitrile nanofibers fabricated by the electrospinning technique serve as a robust support for iron oxide precursors during the hydrothermal process and successfully limit the aggregation of nanoparticles at the following carbonization step. The best materials were optimized under a carbonization condition of 600 °C for 12 h. X-ray diffraction and electron microscopy studies confirm the formation of a maghemite structure standing on the surface of CNFs. The average size of γ-Fe2O3 nanoparticles is below 100 nm, whereas CNFs are ∼150 nm in diameter. In comparison with aggregated bare iron oxide nanoparticles, the as-prepared carbon-maghemite nanofibers exhibit a higher surface area and greatly improved electrochemical performance (>830 mAh g(-1) at 50 mA g(-1) for 40 cycles and high rate capacity up to 5 A g(-1) in the voltage range of 0.005-3 V vs Li). The greatly enhanced electrochemical performance is attributed to the unique one-dimensional nanostructure and the limited aggregation of nanoparticles.

The magnetic and oxidation behavior of bare and silica-coated iron oxide nanoparticles synthesized by reverse co-precipitation of ferrous ion (Fe2+) in ambient atmosphere

The synthesis of iron oxide nanoparticles, i.e., magnetite was attempted by using only ferrous ion (Fe2+) as a magnetite precursor, under an ambient atmosphere. The room temperature reverse co-precipitation method was used, by applying two synthesis protocols. The freshly prepared iron oxide was also immediately coated with Stöber silica (SiO2) layer, forming the coreshell structure. The phase, stoichiometry, crystallite and the particle size of the synthesized powders were determined by using X-ray diffraction (XRD) and transmission electron microscope (TEM), while the magnetic and oxidation behaviors were studied by using the vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. Based on the results, the bare iron oxide nanoparticles are in the stoichiometry between the magnetite and the maghemite stoichiometry, i.e., oxidation occurs. This oxidation is depending on the synthesis protocols used. With the silica coating, the oxidation can be prevented, as suggested by the fits of Mössbauer spectra and low temperature magnetic measurement.

Effect of Surface Modification on Magnetization of Iron Oxide Nanoparticle Colloids

Magnetic iron oxide nanoparticles have numerous applications in the biomedical field, some more mature, such as contrast agents in magnetic resonance imaging (MRI), and some emerging, such as heating agents in hyperthermia for cancer therapy. In all of these applications, the magnetic particles are coated with surfactants and polymers to enhance biocompatibility, prevent agglomeration, and add functionality. However, the coatings may interact with the surface atoms of the magnetic core and form a magnetically disordered layer, reducing the total amount of the magnetic phase, which is the key parameter in many applications. In the current study, amine and carboxyl functionalized and bare iron oxide nanoparticles, all suspended in water, were purchased and characterized. The presence of the coatings in commercial samples was verified with X-ray photoelectron spectroscopy (XPS). The class of iron oxide (magnetite) was verified via Raman spectroscopy and X-ray diffraction. In addition to these, in-house prepared iron oxide nanoparticles coated with oleic acid and suspended in heptane and hexane were also investigated. The saturation magnetization obtained from vibrating sample magnetometry (VSM) measurements was used to determine the effective concentration of magnetic phase in all samples. The Tiron chelation test was then utilized to check the real concentration of the iron oxide in the suspension. The difference between the concentration results from VSM and the Tiron test confirmed the reduction of magnetic phase of magnetic core in the presence of coatings and different suspension media. For the biocompatible coatings, the largest reduction was experienced by amine particles, where the ratio of the effective weight of magnetic phase reported to the real weight was 0.5. Carboxyl-coated samples experienced smaller reduction with a ratio of 0.64. Uncoated sample also exhibits a reduction with a ratio of 0.6. Oleic acid covered samples show a solvent-depended reduction with a ratio of 0.5 in heptane and 0.4 in hexane. The corresponding effective thickness of the nonmagnetic layer between magnetic core and surface coating was calculated by fitting experimentally measured magnetization to the modified Langevin equation.

Fabrication of iron oxide/silica core–shell nanoparticles and their magnetic characteristics

Magnetic core–shell particles, each with a single iron oxide nanoparticle core, were prepared by the reverse microemulsion method. By using 1-butanol as a co-surfactant, one can effectively control the particle size ranging from 60 to 185nm. The mechanism of incorporation of the hydrophobic nanoparticles in the center of a colloidal particle was discussed. The magnetic characteristics of the bare iron oxide nanoparticles and core–shell colloidal particles were studied by SQUID measurements. Superparamagnetic behavior has been found, with a blocking temperature of 200 and 100K respectively. Under an external magnetic field, the as-prepared colloidal particles can assemble along the field direction to form linear structure. These give us a good chance to control the assembly of these colloidal particles by using an external field.

Potential application of superparamagnetic nanoparticles for extraction of bacterial genomic DNA from contaminated food and environmental samples

Isolation of high-molecular-weight DNA is essential for many molecular biology applications. Owing to the presence of polymerase chain reaction (PCR) inhibitors, there is a scarcity of suitable protocols for PCR-ready DNA extraction from food and natural environments. The conventional chemical methods of DNA extraction are time consuming and laborious and the yield is very low. Thus the aim of this research was to develop a simple, rapid, cost-effective method of genomic DNA extraction from food (milk and fruit juice) and environmental (pond water) samples and to detect bacterial contaminants present in those samples. This approach is efficient for both Gram-positive and Gram-negative bacteria from all the studied samples. Herein super paramagnetic bare iron oxide nanoparticles were implemented for bacterial genomic DNA isolation. The method was also compared to the conventional phenol-chloroform method in the context of quality, quantity and timing process. This method took only half an hour or less to obtain high-molecular-weight purified DNA from minimum bacterial contamination. Additionally, the method was directly compatible to PCR amplification. The problem of availability of suitable generalized methods for DNA isolation from various samples including food and environmental has been solved by a nanobiotechnological approach that may prove to be extremely useful in biotechnological applications.

Effect of silica capping on the oxidation of Fe3O4nanoparticles in dispersion revealed by x-ray absorption spectroscopy

Fe${}_{3}$O${}_{4}$ nanoparticles have been investigated as they are biocompatible and their surface can be functionalized. We synthesized iron oxide nanoparticles using a water-in-oil microemulsion method. Bare and silica-coated iron oxide nanoparticles of a core size of 6 nm dispersed in ethanol have been investigated by means of x-ray absorption spectroscopy (XAS). Due to a dedicated experimental setup the particles can be measured directly in dispersion. XAS allows us to disentangle the contributions of the Fe${}^{2+}$ and Fe${}^{3+}$ ions and therefore to estimate the amount of Fe${}_{3}$O${}_{4}$ in the particles. In case of the silica coated particles a high amount of magnetite was obtained. In contrast, the bare nanoparticles showed indications of a further oxidation into $\ensuremath{\gamma}$-Fe${}_{2}$O${}_{3}$ even in dispersion.

Synthesis, characterization and antibacterial activity of superparamagnetic nanoparticles modified with glycol chitosan

Iron oxide nanoparticles (IONPs) were synthesized by coprecipitation of iron salts in alkali media followed by coating with glycol chitosan (GC-coated IONPs). Both bare and GC-coated IONPs were subsequently characterized and evaluated for their antibacterial activity. Comparison of Fourier transform infrared spectra and thermogravimetric data of bare and GC-coated IONPs confirmed the presence of GC coating on IONPs. Magnetization curves showed that both bare and GC-coated IONPs are superparamagnetic and have saturation magnetizations of 70.3 and 59.8 emu g−1, respectively. The IONP size was measured as ∼8–9 nm by transmission electron microscopy, and their crystal structure was assigned to magnetite from x-ray diffraction patterns. Both bare and GC-coated IONPs inhibited the growths of Escherichia coli ATCC 8739 and Salmonella enteritidis SE 01 bacteria better than the antibiotics linezolid and cefaclor, as evaluated by the agar dilution assay. GC-coated IONPs showed higher potency against E. coli O157:H7 and Staphylococcus aureus ATCC 10832 than bare IONPs. Given their biocompatibility and antibacterial properties, GC-coated IONPs are a potential nanomaterial for in vivo applications.

Interaction of bare and gold-coated superparamagnetic iron oxide nanoparticles with fetal bovine serum

Superparamagnetic iron oxide nanoparticles (SPIONs) are being increasingly used in various biomedical processes such as hyperthermia, cell and protein separation, enhancing resolution of magnetic resonance imaging and drug delivery. Here, SPIONs were prepared by optimized co-precipitation of iron chlorides in basic medium and then coated with gold. Bare SPIONs and Aucoated SPIONs were characterized by TEM before incubation with fetal bovine serum for 0.5, 1, 2, 4, 8 and 24 h. After these interaction times, the mixture was deposed on a small column in a strong magnetic field (MACS®system). The SPIONs were retained; different washing fractions were collected and studied by UV-Vis spectroscopy and by 1D gel electrophoresis. The study revealed the presence of proteins in the washing solutions and confirmed the strong interaction of the protein with the SPIONs.

Magnetic Nanoparticles: A Versatile Method for the Reductive, One‐Pot Synthesis of Bare, Hydrophilic and Hydrophobic Magnetite Nanoparticles (Adv. Funct. Mater. 8/2011)

AbstractA biocompatible, reliable, and particularly versatile synthesis of magnetic iron oxide nanoparticles (IONPs) is presented that uses iron(III) acetylacetonate Fe(acac)3 as an iron precursor and sodium borohydride as a reducing agent. Both the reaction temperature and the concentration of the reducing agent have considerable effects on the IONP size. These dependencies can be used to prepare IONPs ranging in size from 5 to 8 nm, as determined by transmission electron microscopy (TEM). Synthesis at room temperature or with higher sodium borohydride concentrations always resulted in smaller particle sizes. Powder X‐ray diffraction patterns show the presence of an iron oxide phase with a cubic unit cell and allow for the determination of the lattice parameters and average crystallite sizes for all synthesized IONPs. Transmission Mössbauer spectroscopy shows that the as‐synthesized IONPs are pure magnetite (Fe3O4) and is further used to elucidate the reaction pathway by analyzing iron intermediates formed prior to nanoparticle formation and precipitation. TEM and high‐resolution TEM reveal quasi‐spherical shapes and lattice fringes for most IONPs. With only minor modifications of the synthesis procedure, this versatile, one‐pot synthesis is proven to be suitable for the production of bare (uncoated) IONPs, IONPs with hydrophilic poly(ethylene glycol), L‐arginine, and L‐glutamic acid coatings, as well as IONPs with hydrophobic coatings such as oleic acid. All coated IONPs were characterized by FT‐IR spectroscopy. In addition, the bare IONPs could easily be modified post‐synthesis with a suitable capping agent using ultrasonication. To verify the biocompatibility of the IONPs, in vitro cytotoxicity studies were carried out on bare IONPs with intestinal (Caco2) and liver epithelial (HepG2) cell cultures using an 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Phase contrast microscopy after hematoxylin‐eosin staining showed the intact morphology of the Caco2 and HepG2 cells treated with IONPs.

A Versatile Method for the Reductive, One‐Pot Synthesis of Bare, Hydrophilic and Hydrophobic Magnetite Nanoparticles

AbstractA biocompatible, reliable, and particularly versatile synthesis of magnetic iron oxide nanoparticles (IONPs) is presented that uses iron(III) acetylacetonate Fe(acac)3 as an iron precursor and sodium borohydride as a reducing agent. Both the reaction temperature and the concentration of the reducing agent have considerable effects on the IONP size. These dependencies can be used to prepare IONPs ranging in size from 5 to 8 nm, as determined by transmission electron microscopy (TEM). Synthesis at room temperature or with higher sodium borohydride concentrations always resulted in smaller particle sizes. Powder X‐ray diffraction patterns show the presence of an iron oxide phase with a cubic unit cell and allow for the determination of the lattice parameters and average crystallite sizes for all synthesized IONPs. Transmission Mössbauer spectroscopy shows that the as‐synthesized IONPs are pure magnetite (Fe3O4) and is further used to elucidate the reaction pathway by analyzing iron intermediates formed prior to nanoparticle formation and precipitation. TEM and high‐resolution TEM reveal quasi‐spherical shapes and lattice fringes for most IONPs. With only minor modifications of the synthesis procedure, this versatile, one‐pot synthesis is proven to be suitable for the production of bare (uncoated) IONPs, IONPs with hydrophilic poly(ethylene glycol), L‐arginine, and L‐glutamic acid coatings, as well as IONPs with hydrophobic coatings such as oleic acid. All coated IONPs were characterized by FT‐IR spectroscopy. In addition, the bare IONPs could easily be modified post‐synthesis with a suitable capping agent using ultrasonication. To verify the biocompatibility of the IONPs, in vitro cytotoxicity studies were carried out on bare IONPs with intestinal (Caco2) and liver epithelial (HepG2) cell cultures using an 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Phase contrast microscopy after hematoxylin‐eosin staining showed the intact morphology of the Caco2 and HepG2 cells treated with IONPs.

Superparamagnetic iron oxide nanoparticles change endothelial cell morphology and mechanics via reactive oxygen species formation

Superparamagnetic iron oxide nanoparticles are used in various medical applications including magnetic resonance imaging, magnetic hyperthermia, and targeted drug and gene delivery. When used in vivo, these nanoparticles interact with endothelial cells lining all blood vessels, therefore it is crucial to understand endothelial cell functional changes and toxicity upon nanoparticle exposure. We incubated porcine aortic endothelial cells with varying concentrations of bare iron oxide nanoparticles (20-40 nm), and measured cellular reactive oxygen species (ROS) formation, morphology and cytoskeletal organization, death, and elastic modulus. Intracellular ROS increased more than 800% after 3 h of nanoparticle exposure (0.5 mg mL(-1)). Endothelial cells elongated to more than twice their initial length by 12 h, and actin stress fibers formed within the cells. This change in the actin cytoskeleton increased cell elastic modulus by 50%. When ROS formation was blocked using scavengers, initial cell morphology and the actin cytoskeleton remained intact, and cell viability increased. These studies suggest that iron oxide nanoparticles induce ROS formation, which disrupts the actin cytoskeleton and alters endothelial cell morphology and mechanics. If ROS formation is decreased using ROS inhibitors, either as a component of the nanoparticle coating or by systemic administration, higher nanoparticle concentrations might be used with greater efficacy and diminished side effects.

Magnetic behavior of iron oxide nanoparticle–biomolecule assembly

Iron oxide nanoparticles of 8–20 nm in size were investigated as an assembly with biomolecules synthesized in an aqueous solution. The magnetic behavior of the biomolecule–nanoparticles assembly depends sensitively on the morphology and hence the distribution of the nanoparticles, where the dipole coupling between the nanoparticles governs the overall magnetic behavior. In assemblies of iron oxide nanoparticles with trypsin, we observe a formation of unusual self-alignment of nanoparticles within trypsin molecules. In such an assembly structure, the magnetic particles tend to exhibit a lower spin-glass transition temperature than as-synthesized bare iron oxide nanoparticles probably due to reduced interparticle couplings within the molecular matrix. The observed self-alignment of nanoparticles in biomolecules may be a useful approach for directed nanoparticles assembly.