Suspensions Of Iron Oxide Nanoparticles Research Articles

Field-induced macroscopic flow of a dilute self-assembling magnetic colloid under rotating magnetic fields

Flow generation by colloidal motors activated by external stimuli is an important issue for active matter physics and several nanotechnological or biomedical applications. For instance, flow recirculation generated by rotating magnetic self-assemblies allows effective ‘pumping’ of a thrombolytic drug towards a blood clot along a blocked vessel. However, the physics of the flow generation in this case remains still poorly explored. This study is focused on the generation of a recirculation flow of a magnetic colloid (aqueous suspension of iron oxide nanoparticles with partially screened electrostatic repulsion) within a closed microfluidic channel via application of an external rotating magnetic field. The colloid undergoes reversible phase separation manifested through the appearance of micron-sized elongated aggregates. They synchronously rotate with the magnetic field and can generate macroscopic flows only in the presence of gradients of the aggregate concentration across the channel induced by superposition of a weak magnetic field gradient to the homogeneous rotating field. We achieve recirculation flows with a characteristic speed ${\sim} 5{-}8\;{\rm \mu}\textrm{m}\;{\textrm{s}^{ - \textrm{1}}}$ at low magnetic field amplitude and frequency ( ${H_0} \approx 3{-}10\;\textrm{kA}\;{\textrm{m}^{ - 1}}$ , ${f = 5{-}15\ \textrm{Hz}}$ ) at low nanoparticle volume fraction ${\varphi _p} = (1.6{-}3.2) \times {10^{ - 3}}$ . The concentration and velocity profiles have been assessed experimentally through particle tracking and particle image velocimetry, and have also been computed using the hydrodynamic diffusion approach coupled with the momentum balance equation with a magnetic torque term. The model correctly reproduces the shape of the experimental concentration and velocity fields and explains complex behaviours of the average recirculation speed as a function of governing parameters ( ${H_0}$ , f, ${\varphi _p}$ , channel size).

Kinetic and Parametric Analysis of the Separation of Ultra-Small, Aqueous Superparamagnetic Iron Oxide Nanoparticle Suspensions under Quadrupole Magnetic Fields.

Superparamagnetic iron oxide nanoparticles (SPIONs) have gathered tremendous scientific interest, especially in the biomedical field, for multiple applications, including bioseparation, drug delivery, etc. Nevertheless, their manipulation and separation with magnetic fields are challenging due to their small size. We recently reported the coupling of cooperative magnetophoresis and sedimentation using quadrupole magnets as a promising strategy to successfully promote SPION recovery from media. However, previous studies involved SPIONs dispersed in organic solvents (non-biocompatible) at high concentrations, which is detrimental to the process economy. In this work, we investigate, for the first time, the magnetic separation of 20 nm and 30 nm SPIONs dispersed in an aqueous medium at relatively low concentrations (as low as 0.5 g·L-1) using our custom, permanent magnet-based quadrupole magnetic sorter (QMS). By monitoring the SPION concentrations along the vessel within the QMS, we estimated the influence of several variables in the separation and analyzed the kinetics of the process. The results obtained can be used to shed light on the dynamics and interplay of variables that govern the fast separation of SPIONs using inexpensive permanent magnets.

In vitro germination and growth of maize and lettuce seeds exposed to iron oxide magnetic nanoparticles

Iron is a micronutrient essential for optimal plant development, nevertheless, due to their low solubility it is poorly available to plants, affecting many agronomically important crops. Nanofertilizers are nanoparticles that have been used as an alternative for the release of micro and macronutrients necessary for plant nutrition. Therefore, in this research we evaluated the effect of the application of aqueous suspensions of iron oxide (magnetite-maghemite) nanoparticles stabilized with chitosan on the germination and growth of Maize (Zea mays L.) and Lettuce (Lactuca sativa L.) plants at in vitro level. Preliminary results suggest that for aqueous nanoparticle suspensions with iron contents below 50 ppm there is no evidence of negative effects on the seed germination process and on the growth of maize seedlings. Similarly, it was determined that there is no phytotoxic effect of the suspensions on Lettuce seeds.

Comparative Characterization of Aqueous Suspensions of Magnetic Iron Oxide Nanoparticles with Different Phase Compositions

Comparative Characterization of Aqueous Suspensions of Magnetic Iron Oxide Nanoparticles with Different Phase Compositions

Nano-colloid based suspensions and emulsions used as means for enhanced oil recovery

Aqueous solutions of polyphenols extracted from parsley leaves are mixed with solution of ferric chloride hexahydrate to synthesize suspensions of polyphenol-coated iron oxide nanoparticles, which are then used to prepare Pickering oil (n-decane)-in water emulsions. The performance of the nano-colloid suspensions and emulsions as agents of enhanced oil recovery (EOR) is assessed with secondary imbibition tests performed under constant flow rate on a glass-etched pore network, after a drainage / primary imbibition cycle for paraffin oil / brine (0.25M NaCl solution) system. The transient changes of the fluid saturation profile along with the pressure drop across the porous medium are recorded. Comparative analysis of the oil recovery efficiency attained with nano-colloid suspensions of varying iron concentration, and Pickering emulsion, enables us to classify them, and select the most efficient ones for further studies.

Fixed magnetic nanoparticles: Obtaining anisotropy energy density from high field magnetization

A simple method is proposed to obtain the effective anisotropy energy density Keff of an assembly of randomly oriented magnetic nanoparticles, from their hysteresis loops. It involves the fitting of a high field asymptotic expression of the magnetization in inverse powers of the applied field H, up to H−3. This is derived from the partition function formalism and the Stoner–Wohlfarth model for single domain nanoparticles. This method can be applied to ferrogels, frozen ferrofluids or magnetic nanoparticles powder (or any system where the nanoparticles are fixed in random directions, and not allowed to rotate), when dipolar interactions can be neglected. As a proof of concept, it is applied to a suspension of iron oxide nanoparticles in hexane, at different temperatures, obtaining the anisotropy energy density Keff as a function of temperature below the fusion point.

Magnetic Hyperthermia Nanoarchitectonics via Iron Oxide Nanoparticles Stabilised by Oleic Acid: Anti-Tumour Efficiency and Safety Evaluation in Animals with Transplanted Carcinoma

In this study, we developed iron oxide nanoparticles stabilised with oleic acid/sodium oleate that could exert therapeutic effects for curing tumours via magnetic hyperthermia. A suspension of iron oxide nanoparticles was produced and characterised. The toxicity of the synthesised composition was examined in vivo and found to be negligible. Histological examination showed a low local irritant effect and no effect on the morphology of the internal organs. The efficiency of magnetic hyperthermia for the treatment of transplanted Walker 256 carcinoma was evaluated. The tumour was infiltrated with the synthesised particles and then treated with an alternating magnetic field. The survival rate was 85% in the studied therapy group of seven animals, while in the control group (without treatment), all animals died. The physicochemical and pharmaceutical properties of the synthesised fluid and the therapeutic results, as seen in the in vivo experiments, provide insights into therapeutic hyperthermia using injected magnetite nanoparticles.

Approaches on Ferrofluid Synthesis and Applications: Current Status and Future Perspectives.

Ferrofluids are colloidal suspensions of iron oxide nanoparticles (IONPs) within aqueous or nonaqueous liquids that exhibit strong magnetic properties. These magnetic properties allow ferrofluids to be manipulated and controlled when exposed to magnetic fields. This review aims to provide the current scope and research opportunities regarding the methods of synthesis of nanoparticles, surfactants, and carrier liquids for ferrofluid production, along with the rheology and applications of ferrofluids within the fields of medicine, water treatment, and mechanical engineering. A ferrofluid is composed of IONPs, a surfactant that coats the magnetic IONPs to prevent agglomeration, and a carrier liquid that suspends the IONPs. Coprecipitation and thermal decomposition are the main methods used for the synthesis of IONPs. Despite the fact that thermal decomposition provides precise control on the nanoparticle size, coprecipitation is the most used method, even when the oxidation of iron can occur. This oxidation alters the ratio of maghemite/magnetite, influencing the magnetic properties of ferrofluids. Strategies to overcome iron oxidation have been proposed, such as the use of an inert atmosphere, adjusting the Fe(II) and Fe(III) ratio to 1:2, and the exploration of other metals with the oxidation state +2. Surfactants and carrier liquids are chosen according to the ferrofluid application to ensure stability. Hence, a compatible carrier liquid (polar or nonpolar) is selected, and then, a surfactant, mainly a polymer, is embedded in the IONPs, providing a steric barrier. Due to the variety of surfactants and carrier liquids, the rheological properties of ferrofluids are an important response variable evaluated when synthesizing ferrofluids. There are many reported applications of ferrofluids, including biosensing, medical imaging, medicinal therapy, magnetic nanoemulsions, and magnetic impedance. Other applications include water treatment, energy harvesting and transfer, and vibration control. To progress from synthesis to applications, research is still ongoing to ensure control of the ferrofluids’ properties.

Impact of Fe3O4 nanoparticles on wheat and barley seeds germination and early growth

This study investigated the effect of Fe3O4 nanoparticles on the rate of germination and growth of wheat and barley seeds. Fe3O4 magnetic nanoparticles were synthesized by using the chemical co-precipitation technique. Based on structural characterization and morphology analysis of nanoparticles were by X-Ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscope (TEM), it was demonstrated that the major amount of the particles is in the range of 20–30 nm with spherical shape. Different concentrations of Iron oxide nanoparticle suspensions were applied to wheat and barley genotypes on seedlings stage. The results demonstrate that this treatment has a positive effect on seed germination. Plants treated with Fe3O4 nanoparticles had considerably higher germination rates, as well as root and coleoptile length.

Folic acid conjugation of magnetite nanoparticles using pulsed electrohydraulic discharges

The sonochemical coprecipitation reaction with moderate ultrasound irradiation in a low vacuum environment was used to obtain aqueous colloidal suspensions of iron oxide nanoparticles (IONPs). The synthesized magnetite nanoparticles were conjugated directly by folic acid using electrohydraulic discharges as a processing technique before modification of the surface of the nanoparticles. Electrohydraulic discharges were applied in two operational modes with high and low power pulsed direct currents between the electrodes. The physical and chemical properties of the obtained samples were studied using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The investigation proved an inverse cubic spinel structure of magnetite with folic acid attachment to the magnetite surface (mean crystallite diameter in the samples, D, ranges 25?31 nm by XRD and SAXS). It was found that the processing with electrohydraulic discharges increased the colloidal stability of the folic acid-magnetite nanoparticle dispersions.

Magnetic nanoparticle hyperthermia for treating locally advanced unresectable and borderline resectable pancreatic cancers: the role of tumor size and eddy-current heating

Purpose Tumor volume largely determines the success of local control of borderline resectable and locally advanced pancreatic cancer with current therapy. We hypothesized that a tumor-mass normalized dose of magnetic nanoparticle hyperthermia (MNPH) with alternating magnetic fields (AMFs) reduces the effect of tumor volume for treatment. Methods 18 female athymic nude mice bearing subcutaneous MiaPaCa02 human xenograft tumors were treated with MNPH following intratumor injections of 5.5 mg Fe/g tumor of an aqueous suspension of magnetic iron-oxide nanoparticles. Mice were randomly divided into control (n = 5) and treated groups having small (0.15 ± 0.03 cm3, n = 4) or large (0.30 ± 0.06 cm3, n = 5) tumors. We assessed the clinical feasibility of this approach and of pulsed AMF to minimize eddy current heating using a finite-element method to solve a bioheat equation for a human-scale multilayer model. Results Compared to the control group, both small and large MiaPaCa02 subcutaneous tumors showed statistically significant growth inhibition. Conversely, there was no significant difference in tumor growth between large and small tumors. Both computational and xenograft models demonstrated higher maximum tumor temperatures for large tumors compared to small tumors. Computational modeling demonstrates that pulsed AMF can minimize nonspecific eddy current heating. Conclusions MNPH provides an advantage to treat large tumors because the MION dose can be adjusted to increase power. Pulsed AMF, with adjusted treatment time, can enhance MNPH in challenging cases such as low MION dose in the target tissue and/or large patients by minimizing nonspecific eddy current heating without sacrificing thermal dose to the target. Nanoparticle heterogeneity in tumors remains a challenge for continued research.

Using magnetic particle imaging systems to localize and guide magnetic hyperthermia treatment: tracers, hardware, and future medical applications.

Magnetic fluid hyperthermia (MFH) treatment makes use of a suspension of superparamagnetic iron oxide nanoparticles, administered systemically or locally, in combination with an externally applied alternating magnetic field, to ablate target tissue by generating heat through a process called induction. The heat generated above the mammalian euthermic temperature of 37°C induces apoptotic cell death and/or enhances the susceptibility of the target tissue to other therapies such as radiation and chemotherapy. While most hyperthermia techniques currently in development are targeted towards cancer treatment, hyperthermia is also used to treat restenosis, to remove plaques, to ablate nerves and to alleviate pain by increasing regional blood flow. While RF hyperthermia can be directed invasively towards the site of treatment, non-invasive localization of heat through induction is challenging. In this review, we discuss recent progress in the field of RF magnetic fluid hyperthermia and introduce a new diagnostic imaging modality called magnetic particle imaging that allows for a focused theranostic approach encompassing treatment planning, treatment monitoring and spatially localized inductive heating.

Biocompatible Layers Obtained from Functionalized Iron Oxide Nanoparticles in Suspension

Iron oxide nanoparticles have been extensively studied for challenges in applicable areas such as medicine, pharmacy, and the environment. The functionalization of iron oxide nanoparticles with dextran opens new prospects for application. Suspension characterization methods such as dynamic light scattering (DLS) and zeta potential (ZP) have allowed us to obtain information regarding the stability and hydrodynamic diameter of these suspended particles. For rigorous characterization of the suspension of dextran-coated iron oxide nanoparticles (D-MNPs), studies have been performed using ultrasound measurements. The results obtained from DLS and ZP studies were compared with those obtained from ultrasound measurements. The obtained results show a good stability of D-MNPs. A comparison between the D-MNP dimension obtained from transmission electron microscopy (TEM), X-ray diffraction (XRD), and DLS studies was also performed. A scanning electron spectroscopy (SEM) image of a surface D-MNP layer obtained from the stable suspension shows that the particles are spherical in shape. The topographies of the elemental maps of the D-MNP layer showed a uniform distribution of the constituent elements. The homogeneity of the layer was also observed. The morphology of the HeLa cells incubated for 24 and 48 h with the D-MNP suspension and D-MNP layers did not change relative to the morphology presented by the control cells. The cytotoxicity studies conducted at different time intervals have shown that a slight decrease in the HeLa cell viability after 48 h of incubation for both samples was observed.

Influence of pre-sowing priming on the parameters of Pisum sativum seedlings

One of the important methods of increasing the yield of cultivated plants is to reduce the yield of crops is pre-sowing treatment of seeds with modern preparations containing various elements and compounds in the nanoform. The aim of the work is to study the influence of pre-sowing treatment of pea seeds by suspension of iron and silicon oxide nanoparticles on germination and morphometric parameters of seedlings. As a result of the experiments with different compositions of seed treatment, it was observed that in the variants of the experiment using a mix of NPsSiO2 and Fe3O4, as well as a variant of Fe3O4 in a concentration of 10−3 mg/l, the germination of beans reached maximum values. In the course of the experiment in conditions of the laboratory experiment studied the effect of processing on pigments. The restructuring of the pigment apparatus was largely associated with an increase in total chlorophyll and carotenoids against the background of the use of a whole range of solutions for treatment with the maximum effect of increasing their concentration when using Fe3O4 (10−3 mg/l), SiO2 (10−3 mg/l) and SiO2 (10−4 mg/l) by the 35th day of the experiment in the green mass of plants.

Electro-optic switching and memory effect in suspension of ferroelectric liquid crystal and iron oxide nanoparticles

In this work, impact of dispersion of iron oxide nanoparticles (Fe2O3 NPs) into ferroelectric liquid crystal (FLC) SCE-13 mixture on the electro-optical and dielectric properties has been studied. It has been found that the dispersion of Fe2O3 NPs in host FLC matrix exhibits pronounced influence on response time, spontaneous polarization, rotational viscosity and voltage required for switching the FLC molecules. Also dispersed system shows memory effect as confirmed by the optical texture and dielectric permittivity studies. Effort has been made to explain the experimental results as for as possible.

Biologically safe colloidal suspensions of naked iron oxide nanoparticles for in situ antibiotic suppression

A category of naked maghemite nanoparticles (γ-Fe2O3), named surface active maghemite nanoparticles (SAMNs), is characterized by biological safety, high water colloidal stability and a surface chemistry permitting the binding of ligands. In the present study, the interaction between SAMNs and an antibiotic displaying chelating properties (oxytetracycline, OxyTC) was extensively structurally and magnetically characterized. OxyTC emerged as an ideal probe for providing insights into the colloidal properties of SAMNs. At the same time, SAMNs turned out as an elective tool for water remediation from OxyTC. Therefore, a dilute colloidal suspension of SAMNs was used for the removal of OxyTC in large volume tanks where, to simulate a real in situ application, a population of zebrafish (Danio rerio) was introduced. Interestingly, SAMNs led to the complete removal of the drug without any sign of toxicity for the animal model. Moreover, OxyTC immobilized on SAMNs surface resulted safe for sensitive Escherichia coli bacteria strain. Thus, SAMNs were able to recover the drug and to suppress its antibiotic activity envisaging their feasibility as competitive option for water remediation from OxyTC in more nature related scenarios. The present contribution stimulates the use of novel smart colloidal materials to cope with complex environmental issues.

Oleic Acid Double Coated Fe₃O₄ Nanoparticles as Anti-Melanoma Compounds with a Complex Mechanism of Activity-In Vitro and In Ovo Assessment.

Magnetic iron oxide nanoparticles (MIONPs) were placed in the spotlight lately due to their excellent biocompatibility and the possibility to tailor their magnetic properties making them useful in a plethora of bioapplications, including magnetic resonance imaging and targeted nanoplatforms for anticancer drugs delivery. The aim of the present study consisted in achieving a toxicological profile of the biocompatible colloidal suspension of iron oxide nanoparticles coated with a double layer of oleic acid (Fe₃O₄ @OA) obtained by combustion method by performing in vitro (on human keratinocytes-HaCaT and human and murine melanoma cells) and in ovo studies on chick chorioallantoic membrane (HET-CAM assay). The colloidal suspension obtained proved to be stable in phosphate buffer saline and the size of the nanoparticles were in the range of 30 nm, an optimum size for biomedical applications. Fe₃O₄ @OA colloidal suspension reduced viability of human keratinocytes only at concentrations higher than 25 μg/mL, whereas in the case of melanoma cells the effect was observed at lower doses (starting with 10 μg/mL). An interesting phenomena was detected at the highest concentration tested (50 μg/mL) to all cell lines, more precisely, a particular enucleation process associated only with Fe₃O₄ @OA colloidal suspension stimulation. The irritant potential data evaluated by HET-CAM assay indicated the following hierarchy: Fe₃O₄ < Fe₃O₄ @OA < OA. Our results provide relevant information regarding the mechanism of action of Fe₃O₄ @OA that needs elucidation by future in vitro and in vivo studies.

Particle assembling induced by non-homogeneous magnetic field at transformer oil-based ferrofluid/silicon crystal interface by neutron reflectometry

The effect of magnetic nanoparticle assembly formation at a planar interface between a transformer oil-based ferrofluid and single-crystal silicon under non-homogeneous magnetic fields was studied by specular neutron reflectometry. The ferrofluid probed represents a stable suspension of dispersed iron oxide nanoparticles (characteristic size about 10 nm) coated with oleic acid in a low-polarity liquid carrier (transformer oil). It was shown that the reflectivity curves are sensitive to the application of a non-homogeneous external magnetic field. In particular, at a low magnetic flux density (<35 mT) they are well described in terms of the simplest model of a strict boundary between two semi-infinite homogeneous media. Nevertheless, slight concentrating of the ferrofluid bulk at the interface was detected. At a high magnetic flux density (35–75 mT), the analysis gives a three-layered structure of in-depth profiles of the scattering length density, thus showing the formation of two effective adsorption layers with different content of magnetic nanoparticles in them.

Sensing Coated Iron-Oxide Nanoparticles with Spectral Induced Polarization (SIP): Experiments in Natural Sand Packed Flow-Through Columns.

The development of nanoparticle-based soil remediation techniques is hindered by the lack of accurate in situ nanoparticle (NP) monitoring and characterization methods. Spectral induced polarization (SIP), a noninvasive geophysical technique, offers a promising approach to detect and quantify NPs in porous media. However, its successful implementation as a monitoring tool requires an understanding of the polarization mechanisms, the governing NP-associated SIP responses and their dependence on the stabilizing coatings that are typically used for NPs deployed in environmental applications. Herein, we present SIP responses (0.1-10 000 Hz) measured during injection of a poloxamer-coated superparamagnetic iron-oxide nanoparticle (SPION) suspension in flow-through columns packed with natural sand from the Borden aquifer. An advective-dispersive transport model is fitted to outflow SPION concentration measurements to compute average concentrations over the SIP spatial response domain (within the columns). The average SPION concentrations are compared with the real and imaginary components of the complex conductivity. Excellent correspondence is found between the average SPION concentrations inthe columns and the imaginary conductivity values, suggesting that NP-mediated polarization (that is, charge storage) increases proportionally with increasing SPION concentration. Our results support the possibility of SIP monitoring of spatial and temporal NP distributions, which can be immediately deployed in bench-scale studies with the prospect of future real-world field applications.

Improving the reliability of the iron concentration quantification for iron oxide nanoparticle suspensions: a two-institutions study

Most iron oxide nanoparticles applications, and in special biomedical applications, require the accurate determination of iron content as the determination of particle properties from measurements in dispersions is strongly dependent on it. Inductively coupled plasma (ICP) and spectrophotometry are two typical worldwide used analytical methods for iron concentration determination. In both techniques, precise determination of iron is not straightforward and nanoparticle digestion and dilution procedures are needed prior to analysis. The sample preparation protocol has been shown to be as important as the analytical method when accuracy is aimed as many puzzling reported results in magnetic, colloidal, and structural properties are simply attributable to inadequate dissolution procedures. Therefore, a standard sample preparation protocol is needed to ensure the adequate and complete iron oxide nanoparticle dissolution and to harmonize this procedure. In this work, an interlaboratory evaluation of an optimized iron oxide nanoparticle digestion/dilution protocol was carried out. The presented protocol is simple, inexpensive, and does not involve any special device (as microwave, ultrasound, or other high-priced digestion devices). Then, iron concentration was measured by ICP-OES (performed in ICMM/CSIC-Spain) and spectrophotometry (NanoPET-Germany) and the obtained concentration values were analyzed to determine the most probable error causes. Uncertainty values as low as 1.5% were achieved after the optimized method was applied. Moreover, this article provides a list of recommendations to significantly reduce uncertainty in both sample preparation and analysis procedures.Graphical abstract