Iron oxide-based nanomagnets in nanomedicine: fabrication and applications

Effect of Oleylamine on the Surface Chemistry, Morphology, Electronic Structure, and Magnetic Properties of Cobalt Ferrite Nanoparticles

The influence of oleylamine (OLA) concentration on the crystallography, morphology, surface chemistry, chemical bonding, and magnetic properties of solvothermal synthesized CoFe₂O₄ (CFO) nanoparticles (NPs) has been thoroughly investigated. Varying OLA concentration (0.01-0.1 M) resulted in the formation of cubic spinel-structured CoFe₂O₄ NPs in the size-range of 20-14 (±1) nm. The Fourier transform spectroscopic analyses performed confirmed the OLA binding to the CFO NPs. The thermogravimetric measurements revealed monolayer and multilayer coating of OLA on CFO NPs, which were further supported by the small-angle X-ray scattering measurements. The magnetic measurements indicated that the maximum saturation (M_S) and remanent (M_r) magnetization decreased with increasing OLA concentration. The ratio of maximum dipolar field (H_dip), coercivity (H_C), and exchanged bias field (H_ex) (at 10 K) to the average crystallite size (D_xrd), i.e., (H_dip/D_xrd), (H_C/D_xrd), and (H_ex/D_xrd), increased linearly with OLA concentration, indicating that OLA concurrently controls the particle size and interparticle interaction among the CFO NPs. The results and analyses demonstrate that the OLA-mediated synthesis allowed for modification of the structural and magnetic properties of CFO NPs, which could readily find potential application in electronics and biomedicine.

Gram-Scale Synthesis of Substituted Triarylmethanes

In this paper, a high-yield, open-vessel route for the facile-operational, gram-scale synthesis of functionalized triarylmethanes (TRAMs) is described via silica coated magnetic nanoparticles of modified polyphosphoric acid (NiFe2O4@SiO2-PPA)-mediated intermolecular Friedel-Crafts reaction of substituted arylaldehydes with 2 equivalents of oxygenated arenes under environmentally friendly reaction conditions. Among the overall reaction process, only water was generated as the byproduct. Various reaction conditions are investigated for efficient transformation.

Influences of Dispersions' Shapes and Processing in Magnetic Field on Thermal Conductibility of PDMS-Fe3O4 Composites

Composites of magnetite (Fe3O4) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (α-FeOOH) and spherical hematite (α-Fe2O3), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe3O4 composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.

New Sustainable, Scalable and One-Step Synthesis of Iron Oxide Nanoparticles by Ion Exchange Process

This work introduces an innovative, sustainable, and scalable synthesis of iron oxides nanoparticles (NPs) in aqueous suspension. The method, based on ion exchange process, consists of a one-step procedure, time and energy saving, operating in water and at room temperature, by cheap and renewable reagents. The influence of both oxidation state of the initial reagent and reaction atmosphere is considered. Three kinds of iron nanostructured compounds are obtained (2-lines ferrihydrite; layered-structure iron oxyhydroxide δ-FeOOH; and cubic magnetite), in turn used as precursors to obtain hematite and maghemite NPs. All the produced NPs are characterized by a high purity, small particles dimensions (from 2 to 50 nm), and high specific surface area values up to 420 m²/g, with yields of production >90%. In particular, among the most common iron oxide NPs, we obtained cubic magnetite NPs at room temperature, characterized by particle dimensions of about 6 nm and a surface area of 170 m²/g. We also obtained hematite NPs at very low temperature conditions (that is 2 h at 200 °C), characterized by particles dimensions of about 5 nm with a surface area value of 200 m²/g. The obtained results underline the strength of the synthetic method to provide a new, sustainable, tunable, and scalable high-quality production.

Nanoparticle-Mediated Therapeutic Application for Modulation of Lysosomal Ion Channels and Functions

Applications of nanoparticles in various fields have been addressed. Nanomaterials serve as carriers for transporting conventional drugs or proteins through lysosomes to various cellular targets. The basic function of lysosomes is to trigger degradation of proteins and lipids. Understanding of lysosomal functions is essential for enhancing the efficacy of nanoparticles-mediated therapy and reducing the malfunctions of cellular metabolism. The lysosomal function is modulated by the movement of ions through various ion channels. Thus, in this review, we have focused on the recruited ion channels for lysosomal function, to understand the lysosomal modulation through the nanoparticles and its applications. In the future, lysosomal channels-based targets will expand the therapeutic application of nanoparticles-associated drugs.

Modeling generation and growth of iron oxide nanoparticles from representative precursors through ReaxFF molecular dynamics

Detailed dynamical characterization of the mechanisms responsible for the formation and growth of iron oxide nanoparticles remains a significant challenge not only for experimental techniques but also for theoretical methodologies due to the nanoparticle size, long simulation times, and complexity of the environments. In this work, we have designed a fast computational protocol based on atomistic reactive molecular dynamics, which is capable of simulating the whole synthetic and proliferation process of the nanoparticles (greater than 10 nm) in a homogeneous medium from organometallic precursors. We have defined appropriate growth accelerating strategies based on the observed reactions, which consisted of the formation of Fe-O-Fe bridges, linking separate precursors, and Fe˙ and FeO˙ radicals. This reduced drastically the computational time allowing the simulation of NPs made of thousands of atoms (full nanometric range). We have identified the most probable reaction environments and summarized them under two distinct conditions: reductive and oxidative. The first one leads to the formation of nanoparticles with FeO stoichiometry typical of wustite, whereas the second one stabilizes stoichiometries between Fe₃O₄ (magnetite), and Fe₂O₃ (maghemite). In the latter case, the obtained NPs adopted, from the very early stages of the growth process, a cubic crystalline structure, typical of the oxidized FeOx bulk phases. The excellent agreement of our results with the experimental data demonstrates that the proposed protocol can provide a powerful predictive tool to describe structural features developed by the metal oxide nanoparticles and establish clear structure-property relationships.

Macrofluidic Coaxial Flow Platforms to Produce Tunable Magnetite Nanoparticles: A Study of the Effect of Reaction Conditions and Biomineralisation Protein Mms6

Magnetite nanoparticles' applicability is growing extensively. However, simple, environmentally-friendly, tunable synthesis of monodispersed iron-oxide nanoparticles is challenging. Continuous flow microfluidic synthesis is promising; however, the microscale results in small yields and clogging. Here we present two simple macrofluidics devices (cast and machined) for precision magnetite nanoparticle synthesis utilizing formation at the interface by diffusion between two laminar flows, removing aforementioned issues. Ferric to total iron was varied between 0.2 (20:80 Fe³⁺:Fe²⁺) and 0.7 (70:30 Fe³⁺:Fe²⁺). X-ray diffraction shows magnetite in fractions from 0.2-0.6, with iron-oxide impurities in 0.7, 0.2 and 0.3 samples and magnetic susceptibility increases with increasing ferric content to 0.6, in agreement with each other and batch synthesis. Remarkably, size is tuned (between 20.5 nm to 6.5 nm) simply by increasing ferric ions ratio. Previous research shows biomineralisation protein Mms6 directs magnetite synthesis and controls size, but until now has not been attempted in flow. Here we report Mms6 increases magnetism, but no difference in particle size is seen, showing flow reduced the influence of Mms6. The study demonstrates a versatile yet simple platform for the synthesis of a vast range of tunable nanoparticles and ideal to study reaction intermediates and additive effects throughout synthesis.

Apoptotic lysosomal proton sponge effect in tumor tissue by cationic gold nanorods

Despite the lysosomal "proton sponge hypothesis" being considered to be an additional factor for stimulating the cellular toxicity of nanoparticle-based drug delivery systems, a clear relationship between the massive influx of calcium ions and the proton sponge effect, both of which are associated with cancer cell apoptosis, has still not been elucidated. Cetrimonium bromide (CTAB: cationic quaternary amino group based) gold nanorods possessed a more effective electric surface charge for inducing the lysosomal proton sponge effect than anionic gold nanoparticles. In this aspect, identifying released cytoplasmic Cl^-, arising from the ruptured lysosomal compartment, in the cytoplasm is critical for supporting the "proton sponge hypothesis". This study clarified that the burst release of Cl^-, as a result of lysosomal swelling by CTAB gold nanorods, stimulates the transient receptor potential channels melastatin 2 (TRPM2) channels, and subsequently induces a massive Ca²⁺ influx, which independently increases apoptosis of cancer cells. Although the previous concept of elevated cancer apoptosis acting through the proton sponge effect is unclear, this study supports the evidence that a massive Ca²⁺ influx mediated in response to a burst release of Cl^- significantly influenced cytotoxicity of cancer cells in tumor tissues.

Structural characterization of polysaccharide-coated iron oxide nanoparticles produced by Staphylococcus warneri, isolated from a thermal spring

The biocompatible-coated iron oxide nanoparticles (IONs) have attracted a great interest because of their various applications in biological science and medicine. In most cases, the toxic effect of naked iron oxide nanoparticles is completely cleared by adding a biocompatible coating, such as polysaccharides, polyethylene glycol (PEG), or biosynthesis of biocompatible-coated IONs using microorganisms such as bacteria. In the present study, polysaccharide-coated iron oxide nanoparticles were produced by a strain of Staphylococcus warneri isolated from a thermal spring. For identification of the isolated bacterium, 16S rRNA gene sequencing was done. Characterization of the nanoparticles was performed for the first time, using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray crystallography (XRD), Fourier-transform infrared (FTIR) spectroscopy, vibrating sample magnetometer (VSM), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results indicated that the spherical iron oxide nanoparticles were coated by a polysaccharide (13.6%), which provided a large negative charge of -91 mV and very low saturation magnetization of around 0.28 emu/g. The result of MTT assay on MOLT-4 cell lines showed that the percentage of viability was between 95.6% and 68.9% in the 10-100 µM of nanoparticle concentrations with a high IC ₅₀ value, which makes it appropriate for biomedical applications such as cancer therapy.

Influence of Nontoxic Magnetic Cellulose Nanofibers on Chitosan Based Edible Nanocoating: A Candidate for Improved Mechanical, Thermal, Optical, and Texture Properties

The present work demonstrates the formulation of cellulose nanofiber (CNF) or magnetic cellulose nanofiber (mgCNF) dispersed chitosan-based edible nanocoating with superior mechanical, thermal, optical, and texture properties. The fabrication of mgCNF is successfully achieved through a single-step coprecipitation route, where iron particles get adsorbed onto CNF. The thermal stability of mgCNF is improved considerably, where ∼17% reduction in weight is observed, whereas CNF degrades completely under identical conditions. TGA analysis shows that there is an improvement in thermal stability for both CNF- and mgCNF-reinforced CS nanocoatings, where mgCNF provides more heat dimensional stability than CNF-dispersed CS nanocoatings. Further, the edible nanocoatings are stable even at the temperature of heat treatment such as food sterilization. The mechanical property of the mgCNF-dispersed chitosan (CS) shows a remarkable improvement in tensile strength (57.86 ± 14 MPa) and Young's modulus (2348.52 ± 276 MPa) in comparison to neat CS (6.27 ± 0.7 and 462.36 ± 64 MPa, respectively). To determine the developed materials to be safe for food, the quantification of iron is made by using ICP-MS technique. It is worth mentioning that mgCNF-coated CS helps in improving the texture of cut pineapples in comparison with uncoated pineapple slices under ambient conditions.

Characterization of biogenic Fe (III)-binding exopolysaccharide nanoparticles produced by Ralstonia sp. SK03

A new technological approach to nanoparticle synthesis is using microorganisms, such as bacteria, which have the ability to synthesize nontoxic nanoparticles with high biocompatibility. In addition, bacteria have strict control over size, structure, shape, and dimension of produced nanoparticles. In the present work, Fe (III)-binding exopolysaccharide (Fe-EPS) nanoparticles were biosynthesized by Ralstonia pickettii sp. SK03, a bacterium isolated from a mineral spring. 16S rRNA gene sequencing and biochemical tests were done for identification of the isolated bacterium. For the first time, critical biological and physicochemical properties of this iron oxide nanoparticle were characterized using Fourier Transform Infrared (FTIR) Spectroscopy, Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM), Dynamic Light Scattering (DLS), Thermogravimetric analysis (TGA), X-ray crystallography (XRD), Atomic absorption spectroscopy (AAS), and cell viability assays (MTT assay). The characterization results showed that Fe-EPS nanoparticles were composed of spherical ferrihydrite nanoparticles (with a size range of 1.2-2 nm), trapped in a polysaccharide matrix. The TGA analysis demonstrated that Fe-EPS nanoparticles contained ∼25.2% polysaccharide. Therefore, this polysaccharide matrix showed a very low magnetic saturation value (0.25 emu/g) and a large negative charge of -93.8 mV. In addition, treatment of hepatocarcinoma cell line (Hep-G2) with 1-500 µg/mL concentrations of Fe-EPS nanoparticles caused 40% increase in the cell viability, which indicated that the biosynthesized nanoparticles were nontoxic and biocompatible. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1167-1176, 2018.

In Vitro Carcinoma Treatment Using Magnetic Nanocarriers under Ultrasound and Magnetic Fields

Nowadays, tumor hypoxia has become a more predominant problem for diagnosis as well as treatment of cancer due to difficulties in delivering chemotherapeutic drugs and their carriers to these regions with reduced vasculature and oxygen supply. In such cases, external physical stimulus-mediated drug delivery, such as ultrasound and magnetic fields, would be effective. In this work, the effect of simultaneous exposure of low-intensity pulsed ultrasound and static magnetic field on colon (HCT116) and hepatocellular (HepG2) carcinoma cell inhibition was assessed in vitro. The treatment, in the presence of anticancer drug, with and without magnetic carrier, significantly increased the reactive oxygen species production and hyperpolarized the cancer cells. As a result, a significant increase in cell inhibition, up to 86%, was observed compared to 50% inhibition with bare anticancer drug. The treatment appears to have relatively more effect on HepG2 cells during the initial 24 h than on HCT116 cells. The proposed treatment was also found to reduce cancer cell necrosis and did not show any inhibitory effect on healthy cells (MC3T3). Our in vitro results suggest that this approach has strong application potential to treat cancer at lower drug dosage to achieve similar inhibition and can reduce health risks associated with drugs.

Duplex-imprinted nano well arrays for promising nanoparticle assembly

A large area nano-duplex-imprint technique is presented in this contribution using natural cicada wings as stamps. The glassy wings of the cicada, which are abundant in nature, exhibit strikingly interesting nanopillar structures over their membrane. This technique, with excellent performance despite the nonplanar surface of the wings, combines both top-down and bottom-up nanofabrication techniques. It transitions micro-nanofabrication from a cleanroom environment to the bench. Two different materials, dicing tape with an acrylic layer and a UV optical adhesive, are used to make replications at the same time, thus achieving duplex imprinting. The promise of a large volume of commercial manufacturing of these nanostructure elements can be envisaged through this contribution to speeding up the fabrication process and achieving a higher throughput. The contact angle of the replicated nanowell arrays before and after oxygen plasma was measured. Gold nanoparticles (50 nm) were used to test how the nanoparticles behaved on the untreated and plasma-treated replica surface. The experiments show that promising nanoparticle self-assembly can be obtained.

Redox-active nanomaterials for nanomedicine applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.

Designed synthesis and surface engineering strategies of magnetic iron oxide nanoparticles for biomedical applications

Iron oxide nanoparticles (NPs) hold great promise for future biomedical applications because of their magnetic properties as well as other intrinsic properties such as low toxicity, colloidal stability, and surface engineering capability. Numerous related studies on iron oxide NPs have been conducted. Recent progress in nanochemistry has enabled fine control over the size, crystallinity, uniformity, and surface properties of iron oxide NPs. This review examines various synthetic approaches and surface engineering strategies for preparing naked and functional iron oxide NPs with different physicochemical properties. Growing interest in designed and surface-engineered iron oxide NPs with multifunctionalities was explored in in vitro/in vivo biomedical applications, focusing on their combined roles in bioseparation, as a biosensor, targeted-drug delivery, MR contrast agents, and magnetic fluid hyperthermia. This review outlines the limitations of extant surface engineering strategies and several developing strategies that may overcome these limitations. This study also details the promising future directions of this active research field.

Importance of Molds for Nanoimprint Lithography: Hard, Soft, and Hybrid Molds

Nanoimprint lithography has attracted considerable attention in academic and industrial fields as one of the most prominent lithographic techniques for the fabrication of the nanoscale devices. Effectively controllable shapes of fabricated elements, extremely high resolution, and cost-effectiveness of this especial lithographic system have shown unlimited potential to be utilized for practical applications. In the past decade, many different lithographic techniques have been developed such as electron beam lithography, photolithography, and nanoimprint lithography. Among them, nanoimprint lithography has proven to have not only various advantages that other lithographic techniques have but also potential to minimize the limitations of current lithographic techniques. In this review, we summarize current lithography techniques and, furthermore, investigate the nanoimprint lithography in detail in particular focusing on the types of molds. Nanoimprint lithography can be categorized into three different techniques (hard-mold, soft-mold, and hybrid nanoimprint) depending upon the molds for imprint with different advantages and disadvantages. With numerous studies and improvements, nanoimprint lithography has shown great potential which maximizes its effectiveness in patterning by minimizing its limitations. This technique will surely be the next generation lithographic technique which will open the new paradigm for the patterning and fabrication in nanoscale devices in industry.

Virus-Templated Near-Amorphous Iron Oxide Nanotubes

We present a simple synthesis of iron oxide nanotubes, grown under very mild conditions from a solution containing Fe(II) and Fe(III), on rod-shaped tobacco mosaic virus templates. Their well-defined shape and surface chemistry suggest that these robust bionanoparticles are a versatile platform for synthesis of small, thin mineral tubes, which was achieved efficiently. Various characterization tools were used to explore the iron oxide in detail: Electron microscopy (SEM, TEM), magnetometry (SQUID-VSM), diffraction (XRD, TEM-SAED), electron spectroscopies (EELS, EDX, XPS), and X-ray absorption (XANES with EXAFS analysis). They allowed determination of the structure, crystallinity, magnetic properties, and composition of the tubes. The protein surface of the viral templates was crucial to nucleate iron oxide, exhibiting analogies to biomineralization in natural compartments such as ferritin cages.

Increased transverse relaxivity in ultrasmall superparamagnetic iron oxide nanoparticles used as MRI contrast agent for biomedical imaging

Synthesis of a contrast agent for biomedical imaging is of great interest where magnetic nanoparticles are concerned, because of the strong influence of particle size on transverse relaxivity. In the present study, biocompatible magnetic iron oxide nanoparticles were synthesized by co-precipitation of Fe²⁺ and Fe³⁺ salts, followed by surface adsorption with reduced dextran. The synthesized nanoparticles were spherical in shape, and 12 ± 2 nm in size as measured using transmission electron microscopy; this was corroborated with results from X-ray diffraction and dynamic light scattering studies. The nanoparticles exhibited superparamagnetic behavior, superior T₂ relaxation rate and high relaxivities (r₁  = 18.4 ± 0.3, r₂  = 90.5 ± 0.8 s^-1 mM^-1 , at 7 T). MR image analysis of animals before and after magnetic nanoparticle administration revealed that the signal intensity of tumor imaging, specific organ imaging and whole body imaging can be clearly distinguished, due to the strong relaxation properties of these nanoparticles. Very low concentrations (3.0 mg Fe/kg body weight) of iron oxides are sufficient for early detection of tumors, and also have a clear distinction in pre- and post-enhancement of contrast in organs and body imaging. Many investigators have demonstrated high relaxivities of magnetic nanoparticles at superparamagnetic iron oxide level above 50 nm, but this investigation presents a satisfactory, ultrasmall, superparamagnetic and high transverse relaxivity negative contrast agent for diagnosis in pre-clinical studies. Copyright © 2016 John Wiley & Sons, Ltd.

Liposomes loaded with hydrophilic magnetite nanoparticles: Preparation and application as contrast agents for magnetic resonance imaging

Magnetic fluid-loaded liposomes (MFLs) were fabricated using magnetite nanoparticles (MNPs) and natural phospholipids via the thin film hydration method followed by extrusion. The size distribution and composition of MFLs were studied using dynamic light scattering and spectrophotometry. The effective ranges of magnetite concentration in MNPs hydrosol and MFLs for contrasting at both T2 and T1 relaxation were determined. On T2 weighted images, the MFLs effectively increased the contrast if compared with MNPs hydrosol, while on T1 weighted images, MNPs hydrosol contrasting was more efficient than that of MFLs. In vivo magnetic resonance imaging (MRI) contrasting properties of MFLs and their effects on tumor and normal tissues morphology, were investigated in rats with transplanted renal cell carcinoma upon intratumoral administration of MFLs. No significant morphological changes in rat internal organs upon intratumoral injection of MFLs were detected, suggesting that the liposomes are relatively safe and can be used as the potential contrasting agents for MRI.

Biomedical Applications of Magnetically Functionalized Organic/Inorganic Hybrid Nanofibers

Nanofibers are one-dimensional nanomaterial in fiber form with diameter less than 1 µm and an aspect ratio (length/diameter) larger than 100:1. Among the different types of nanoparticle-loaded nanofiber systems, nanofibers loaded with magnetic nanoparticles have gained much attention from biomedical scientists due to a synergistic effect obtained from the unique properties of both the nanofibers and magnetic nanoparticles. These magnetic nanoparticle-encapsulated or -embedded nanofiber systems can be used not only for imaging purposes but also for therapy. In this review, we focused on recent advances in nanofibers loaded with magnetic nanoparticles, their biomedical applications, and future trends in the application of these nanofibers.

Polysaccharide-Coated Magnetic Nanoparticles for Imaging and Gene Therapy

Today, nanotechnology plays a vital role in biomedical applications, especially for the diagnosis and treatment of various diseases. Among the many different types of fabricated nanoparticles, magnetic metal oxide nanoparticles stand out as unique and useful tools for biomedical applications, because of their imaging characteristics and therapeutic properties such as drug and gene carriers. Polymer-coated magnetic particles are currently of particular interest to investigators in the fields of nanobiomedicine and fundamental biomaterials. Theranostic magnetic nanoparticles that are encapsulated or coated with polymers not only exhibit imaging properties in response to stimuli, but also can efficiently deliver various drugs and therapeutic genes. Even though a large number of polymer-coated magnetic nanoparticles have been fabricated over the last decade, most of these have only been used for imaging purposes. The focus of this review is on polysaccharide-coated magnetic nanoparticles used for imaging and gene delivery.

Magnetosomes extracted from Magnetospirillum magneticum strain AMB-1 showed enhanced peroxidase-like activity under visible-light irradiation

Magnetosomes are intracellular structures produced by magnetotactic bacteria and are magnetic nanoparticles surrounded by a lipid bilayer membrane. Magnetosomes reportedly possess intrinsic enzyme mimetic activity similar to that found in horseradish peroxidase (HRP) and can scavenge reactive oxygen species depending on peroxidase activity. Our previous study has demonstrated the phototaxis characteristics of Magnetospirillum magneticum strain AMB-1 cells, but the mechanism is not well understood. Therefore, we studied the relationship between visible-light irradiation and peroxidase-like activity of magnetosomes extracted from M. magneticum strain AMB-1. We then compared this characteristic with that of HRP, iron ions, and naked magnetosomes using 3,3',5,5'-tetramethylbenzidine as a peroxidase substrate in the presence of H2O2. Results showed that HRP and iron ions had different activities from those of magnetosomes and naked magnetosomes when exposed to visible-light irradiation. Magnetosomes and naked magnetosomes had enhanced peroxidase-like activities under visible-light irradiation, but magnetosomes showed less affinity toward substrates than naked magnetosomes under visible-light irradiation. These results suggested that the peroxidase-like activity of magnetosomes may follow an ordered ternary mechanism rather than a ping-pong mechanism. This finding may provide new insight into the function of magnetosomes in the phototaxis in magnetotactic bacteria.

Multifunctional Nanostructures: Synthesis and Applications

Free identical nanoobjects include metals, semiconductors, magnetic materials, polymers, bio molecules, are integrated together to form as multifunctional nanomaterials (MFNs), in which more than one behaviour can be rendered simultaneously. This summary showcases their exciting properties which are providing the emerging properties in applications like visualizing and targeting in drug delivery, recoverable and reusable photocatalytic materials. Various application areas, where the multifunctional nanomaterials are now getting the constant place in cutting edge technologies, are highlighted. And also in this, various multifunctional materials and their criteria involving during the integration of assorted materials based on their properties and to be applied according to the requirements of the applications are also explained in detail.

Synthesis of oleic acid functionalized Fe3O4 magnetic nanoparticles and studying their interaction with tumor cells for potential hyperthermia applications

In the present study, oleic acid (OA) functionalized Fe3O4 magnetic nanoparticles (MN) were synthesized following modified wet method of MN synthesis. The optimum amount of OA required for capping of MN and the amount of bound and unbound/free OA was determined by thermogravimetric analysis (TGA). Further, we have studied the effect of water molecules, associated with MN, on the variation in their induction heating ability under alternating current (AC) magnetic field conditions. We have employed a new approach to achieve dispersion of OA functionalized MN (MN-OA) in aqueous medium using sodium carbonate, which improves their biological applicability. Interactions amongst MN, OA and sodium carbonate were studied by Fourier transform infrared spectroscopy (FT-IR). Intracellular localization of MN-OA was studied in mouse fibrosarcoma cells (WEHI-164) by prussian blue staining and confocal laser scanning microscopy (CLSM) using nile blue A as a fluorescent probe. Results showed MN-OA to be interacting mainly with the cell membrane. Their hyperthermic killing ability was evaluated in WEHI-164 cells by trypan blue method. Cells treated with MN-OA in combination with induction heating showed decreased viability as compared to respective induction heating controls. These results were supported by altered cellular morphology after treatment of MN-OA in combination with induction heating. Further, the magnitude of apoptosis was found to be ~5 folds higher in cells treated with MN-OA in combination with induction heating as compared to untreated control. These results suggest the efficacy of MN-OA in killing of tumor cells by cellular hyperthermia.

Superparamagnetic iron oxide nanoparticles: amplifying ROS stress to improve anticancer drug efficacy

Superparamagnetic iron oxide nanoparticles (SPION) are an important and versatile nano- platform with broad biological applications. Despite extensive studies, the biological and pharmacological activities of SPION have not been exploited in therapeutic applications. Recently, β-lapachone (β-lap), a novel anticancer drug, has shown considerable cancer specificity by selectively increasing reactive oxygen species (ROS) stress in cancer cells. In this study, we report that pH-responsive SPION-micelles can synergize with β-lap for improved cancer therapy. These SPION-micelles selectively release iron ions inside cancer cells, which interact with hydrogen peroxide (H₂O₂) generated from β-lap in a tumor-specific, NQO1-dependent manner. Through Fenton reactions, these iron ions escalate the ROS stress in β-lap-exposed cancer cells, thereby greatly enhancing the therapeutic index of β-lap. More specifically, a 10-fold increase in ROS stress was detected in β-lap-exposed cells pretreated with SPION-micelles over those treated with β-lap alone, which also correlates with significantly increased cell death. Catalase treatment of cells or administration of an iron chelator can block the therapeutic synergy. Our data suggest that incorporation of SPION-micelles with ROS-generating drugs can potentially improve drug efficacy during cancer treatment, thereby provides a synergistic strategy to integrate imaging and therapeutic functions in the development of theranostic nanomedicine.

Nanocomposites of polymer and inorganic nanoparticles for optical and magnetic applications

This article provides an up-to-date review on nanocomposites composed of inorganic nanoparticles and the polymer matrix for optical and magnetic applications. Optical or magnetic characteristics can change upon the decrease of particle sizes to very small dimensions, which are, in general, of major interest in the area of nanocomposite materials. The use of inorganic nanoparticles into the polymer matrix can provide high-performance novel materials that find applications in many industrial fields. With this respect, frequently considered features are optical properties such as light absorption (UV and color), and the extent of light scattering or, in the case of metal particles, photoluminescence, dichroism, and so on, and magnetic properties such as superparamagnetism, electromagnetic wave absorption, and electromagnetic interference shielding. A general introduction, definition, and historical development of polymer-inorganic nanocomposites as well as a comprehensive review of synthetic techniques for polymer-inorganic nanocomposites will be given. Future possibilities for the development of nanocomposites for optical and magnetic applications are also introduced. It is expected that the use of new functional inorganic nano-fillers will lead to new polymer-inorganic nanocomposites with unique combinations of material properties. By careful selection of synthetic techniques and understanding/exploiting the unique physics of the polymeric nanocomposites in such materials, novel functional polymer-inorganic nanocomposites can be designed and fabricated for new interesting applications such as optoelectronic and magneto-optic applications.