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The preparation procedure of zero magnetic remanence superparamagnetic white paper by means of three-layer membrane configuration (sandwiched structure) is presented. The cellulose acetate fibrous membranes were prepared by electrospinning. The middle membrane layer was magnetically loaded by impregnation with an aqueous ferrofluid of 8 nm magnetic iron oxide nanoparticles colloidally stabilized with a double layer of oleic acid. The nanoparticles show zero magnetic remanence due to their very small diameters and their soft magnetic properties. Changing the ferrofluid magnetic nanoparticle volume fraction, white papers with zero magnetic remanence and tunable saturation magnetization in the range of 0.5–3.5 emu/g were prepared. The dark coloring of the paper owing to the presence of the black magnetite nanoparticles was concealed by the external layers of pristine white cellulose acetate electrospun fibrous membranes. [ABSTRACT FROM AUTHOR]

Ti3C2Tx MXene is one of the most comprehensively studied 2D materials in terms of its adsorptive, transport, and catalytic properties, cytotoxic performance, etc. Still, conventional MXene synthesis approaches provide low single-flake MXene yield and frequently uncontrollable properties, demanding further post-processing. The MXene family also lacks magnetism, which is helpful for producing effective nanoadsorbents as their magnetic decantation is the cheapest and most convenient way to remove the spent adsorbent from water. Composite materials consisting of magnetic nanoparticles grown on top of MXene flakes are commonly used to provide magnetic properties to the resulting nanocomposite. In this paper, we study the possibility to delaminate multilayer Ti3C2Tx MXene sheets directly by growing iron oxide magnetic nanoparticles inside their interlayer spacing. We find out that, with a mass fraction of particles comparable or exceeding that of MXenes, their growth is accompanied by an effective enhancement of single-layer MXene yield and suitable magnetic properties of the resulting composite. The developed approach can be further used for simplifying synthesis protocols to obtain magnetic MXene-based nanoadsorbents with tunable properties. [ABSTRACT FROM AUTHOR]

This paper describes the preparation and obtained magnetic properties of large single domain iron oxide nanoparticles. Such ferrimagnetic particles are particularly interesting for diagnostic and therapeutic applications in medicine or (bio)technology. The particles were prepared by a modified oxidation method of non-magnetic precursors following the green rust synthesis and characterized regarding their structural and magnetic properties. For increasing preparation temperatures (5 to 85 °C), an increasing particle size in the range of 30 to 60 nm is observed. Magnetic measurements confirm a single domain ferrimagnetic behavior with a mean saturation magnetization of ca. 90 Am2/kg and a size-dependent coercivity in the range of 6 to 15 kA/m. The samples show a specific absorption rate (SAR) of up to 600 W/g, which is promising for magnetic hyperthermia application. For particle preparation temperatures above 45 °C, a non-magnetic impurity phase occurs besides the magnetic iron oxides that results in a reduced net saturation magnetization. [ABSTRACT FROM AUTHOR]

This study aimed to develop the method for determination of the ultra-small superparamagnetic iron oxide nanoparticle (USPION)-originated iron (UOI) in the tissues of rats on the basis of the magnetic characteristics (MC) in the liver, left heart ventricle (LHV), kidneys, aorta and blood of Wistar-Kyoto (WKY). Rats were treated intravenously by USPIONs dispersed in saline (transmission electron microscope (TEM) mean size ~30 nm, hydrodynamic size ~51 nm, nominal iron content 1 mg Fe/mL) at the low iron dose of 1 mg/kg. MC in the form of the mass magnetisation (M) versus the magnetic field (H) curves and temperature dependences of M (determined using the SQUID magnetometer), histochemical determination of iron (by Perl's method) and USPION-induced superoxide production (by lucigenin-enhanced chemiluminescence) were investigated 100 min post-infusion. USPIONs significantly elevated superoxide production in the liver, LHV, kidney and aorta vs. the control group. Histochemical staining confirmed the presence of iron in all solid biological samples, however, this method was not suitable to unequivocally confirm the presence of UOI. We improved the SQUID magnetometric method and sample preparation to allow the determination of UOI by measurements of the MC of the tissues at 300 K in solid and liquid samples. The presence of the UOI was confirmed in all the tissues investigated in USPIONs-treated rats. The greatest levels were found in blood and lower amounts in the aorta, liver, LHV and kidneys. In conclusion, we have improved SQUID-magnetometric method to make it suitable for detection of low amounts of UOI in blood and tissues of rats. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles (MNPs) have been studied for diagnostic purposes for decades. Their high surface-to-volume ratio, dispersibility, ability to interact with various molecules and superparamagnetic properties are at the core of what makes MNPs so promising. They have been applied in a multitude of areas in medicine, particularly Magnetic Resonance Imaging (MRI). Iron oxide nanoparticles (IONPs) are the most well-accepted based on their excellent superparamagnetic properties and low toxicity. Nevertheless, IONPs are facing many challenges that make their entry into the market difficult. To overcome these challenges, research has focused on developing MNPs with better safety profiles and enhanced magnetic properties. One particularly important strategy includes doping MNPs (particularly IONPs) with other metallic elements, such as cobalt (Co) and manganese (Mn), to reduce the iron (Fe) content released into the body resulting in the creation of multimodal nanoparticles with unique properties. Another approach includes the development of MNPs using other metals besides Fe, that possess great magnetic or other imaging properties. The future of this field seems to be the production of MNPs which can be used as multipurpose platforms that can combine different uses of MRI or different imaging techniques to design more effective and complete diagnostic tests. [ABSTRACT FROM AUTHOR]

The study investigated the phenomenon of the fast aggregation of single-domain magnetic iron oxide nanoparticles in stable aqueous colloidal suspensions due to the presence of a radio-frequency (RF) magnetic field. Single-domain nanoparticles have specific magnetic properties, especially the unique property of absorbing the energy of such a field and releasing it in the form of heat. The localized heating causes the colloid to become unstable, leading to faster agglomeration of nanoparticles and, consequently, to rapid sedimentation. It has been shown that the destabilization of a stable magnetic nanoparticle colloid by the RF magnetic field can be used for the controlled filtration of larger agglomerates of the colloid solution. Two particular cases of stable colloidal suspensions were considered: a suspension of the bare nanoparticles in an alkaline solution and the silica-stabilized nanoparticles in a neutral solution. The obtained results are important primarily for biomedical applications and wastewater treatment. [ABSTRACT FROM AUTHOR]

Pyrrhotite nanoparticles with 5C and 3C superstructures were synthesized via a simple one-step thermal decomposition method in which hexadecylamine was used as a solvent at various reaction temperatures (TR). Structural analysis showed that at TR = 360 °C, almost uniform in size and shape Fe7S8 nanoparticles with 3C superstructure are formed, and an increase in the reaction temperature leads to the formation of Fe9S10 nanoparticles (5C superstructure), herewith a significant increase in the size of nanoparticles is observed. High-temperature magnetic measurements in 5 repeated heating-cooling cycles revealed that after the first heating branch in the Fe9S10 samples, the λ—Peak transition disappears, and the magnetization has a Weiss-type behavior characteristic of the Fe7S8 sample. The change in the behavior of magnetization can be explained by the redistribution of iron vacancies, which changes the initial phase composition of nanoparticles. [ABSTRACT FROM AUTHOR]

The activation of magnetic nanoparticles in hyperthermia treatment by an external alternating magnetic field is a promising technique for targeted cancer therapy. The external alternating magnetic field generates heat in the tumor area, which is utilized to kill cancerous cells. Depending on the tumor type and site to be targeted, various types of magnetic nanoparticles, with variable coating materials of different shape and surface charge, have been developed. The tunable physical and chemical properties of magnetic nanoparticles enhance their heating efficiency. Moreover, heating efficiency is directly related with the product values of the applied magnetic field and frequency. Protein corona formation is another important parameter affecting the heating efficiency of MNPs in magnetic hyperthermia. This review provides the basics of magnetic hyperthermia, mechanisms of heat losses, thermal doses for hyperthermia therapy, and strategies to improve heating efficiency. The purpose of this review is to build a bridge between the synthesis/coating of magnetic nanoparticles and their practical application in magnetic hyperthermia. [ABSTRACT FROM AUTHOR]

Micromixer technology is a novel approach to manufacture magnetic single-core iron oxide nanoparticles that offer huge potential for biomedical applications. This platform allows a continuous, scalable, and highly controllable synthesis of magnetic nanoparticles with biocompatible educts via aqueous synthesis route. Since each biomedical application requires specific physical and chemical properties, a comprehensive understanding of the synthesis mechanisms is not only mandatory to control the size and shape of desired nanoparticle systems but, above all, to obtain the envisaged magnetic particle characteristics. The accurate process control of the micromixer technology can be maintained by adjusting two parameters: the synthesis temperature and the residence time. To this end, we performed a systematic variation of these two control parameters synthesizing magnetic nanoparticle systems, which were analyzed afterward by structural (transmission electron microscopy and differential sedimentation centrifugation) and, especially, magnetic characterization methods (magnetic particle spectroscopy and AC susceptibility). Furthermore, we investigated the reproducibility of the microtechnological nanoparticle manufacturing process compared to batch preparation. Our characterization demonstrated the high magnetic quality of single-core iron oxide nanoparticles with core diameters in the range of 20 nm to 40 nm synthesized by micromixer technology. Moreover, we demonstrated the high capability of a newly developed benchtop magnetic particle spectroscopy device that directly monitored the magnetic properties of the magnetic nanoparticles with the highest sensitivity and millisecond temporal resolution during continuous micromixer synthesis. [ABSTRACT FROM AUTHOR]

Magnetic polymer gels are a new promising class of nanocomposite gels. In this work, magnetic PEO/iron oxide nanocomposite hydrogels were synthesized using the one-step γ-irradiation method starting from poly(ethylene oxide) (PEO) and iron(III) precursor alkaline aqueous suspensions followed by simultaneous crosslinking of PEO chains and reduction of Fe(III) precursor. γ-irradiation dose and concentrations of Fe3+, 2-propanol and PEO in the initial suspensions were varied and optimized. With 2-propanol and at high doses magnetic gels with embedded magnetite nanoparticles were obtained, as confirmed by XRD, SEM and Mössbauer spectrometry. The quantitative determination of γ-irradiation generated Fe2+ was performed using the 1,10-phenanthroline method. The maximal Fe2+ molar fraction of 0.55 was achieved at 300 kGy, pH = 12 and initial 5% of Fe3+. The DSC and rheological measurements confirmed the formation of a well-structured network. The thermal and rheological properties of gels depended on the dose, PEO concentration and initial Fe3+ content (amount of nanoparticles synthesized inside gels). More amorphous and stronger gels were formed at higher dose and higher nanoparticle content. The properties of synthesized gels were determined by the presence of magnetic iron oxide nanoparticles, which acted as reinforcing agents and additional crosslinkers of PEO chains thus facilitating the one-step gel formation. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles have received remarkable attention in different applications. For biomedical applications, they need to possess suitable core size, acceptable hydrodynamic diameter, high saturation magnetization, and reduced toxicity. Our aim is to control the synthesis parameters of nanostructured iron oxides in order to obtain magnetite nanoparticles in a single step, in environmentally friendly conditions, under inert gas atmosphere. The physical–chemical, structural, magnetic, and biocompatible properties of magnetite prepared by hydrothermal method in different temperature and pressure conditions have been explored. Magnetite formation has been proved by Fourier-transform infrared spectroscopy and X-ray diffraction characterization. It has been found that crystallite size increases with pressure and temperature increase, while hydrodynamic diameter is influenced by temperature. Magnetic measurements indicated that the magnetic core of particles synthesized at high temperature is larger, in accordance with the crystallite size analysis. Particles synthesized at 100 °C have nearly identical magnetic moments, at 20 × 103 μB, corresponding to magnetic cores of 10–11 nm, while the particles synthesized at 200 °C show slightly higher magnetic moments (25 × 103 μB) and larger magnetic cores (13 nm). Viability test results revealed that the particles show only minor intrinsic toxicity, meaning that these particles could be suited for biomedical applications. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4) particles with a diameter around 10 nm have a very low coercivity (Hc) and relative remnant magnetization (Mr/Ms), which is unfavorable for magnetic fluid hyperthermia. In contrast, cobalt ferrite (CoFe2O4) particles of the same size have a very high Hc and Mr/Ms, which is magnetically too hard to obtain suitable specific heating power (SHP) in hyperthermia. For the optimization of the magnetic properties, the Fe2+ ions of magnetite were substituted by Co2+ step by step, which results in a Co doped iron oxide inverse spinel with an adjustable Fe2+ substitution degree in the full range of pure iron oxide up to pure cobalt ferrite. The obtained magnetic nanoparticles were characterized regarding their structural and magnetic properties as well as their cell toxicity. The pure iron oxide particles showed an average size of 8 nm, which increased up to 12 nm for the cobalt ferrite. For ferrofluids containing the prepared particles, only a limited dependence of Hc and Mr/Ms on the Co content in the particles was found, which confirms a stable dispersion of the particles within the ferrofluid. For dry particles, a strong correlation between the Co content and the resulting Hc and Mr/Ms was detected. For small substitution degrees, only a slight increase in Hc was found for the increasing Co content, whereas for a substitution of more than 10% of the Fe atoms by Co, a strong linear increase in Hc and Mr/Ms was obtained. Mössbauer spectroscopy revealed predominantly Fe3+ in all samples, while also verifying an ordered magnetic structure with a low to moderate surface spin canting. Relative spectral areas of Mössbauer subspectra indicated a mainly random distribution of Co2+ ions rather than the more pronounced octahedral site-preference of bulk CoFe2O4. Cell vitality studies confirmed no increased toxicity of the Co-doped iron oxide nanoparticles compared to the pure iron oxide ones. Magnetic heating performance was confirmed to be a function of coercivity as well. The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size. The found heating performance is suitable for magnetic hyperthermia application. [ABSTRACT FROM AUTHOR]

Cancer is a major health concern and the prognosis is often poor. Significant advances in nanotechnology are now driving a revolution in cancer detection and treatment. The goal of this study was to develop a novel hybrid nanosystem for melanoma treatment, integrating therapeutic and magnetic targeting modalities. Hence, we designed long circulating and pH-sensitive liposomes loading both dichloro(1,10-phenanthroline) copper (II) (Cuphen), a cytotoxic metallodrug, and iron oxide nanoparticles (IONPs). The synthetized IONPs were characterized by transmission electron microscopy and dynamic light scattering. Lipid-based nanoformulations were prepared by the dehydration rehydration method, followed by an extrusion step for reducing and homogenizing the mean size. Liposomes were characterized in terms of incorporation parameters and mean size. High Cuphen loadings were obtained and the presence of IONPs slightly reduced Cuphen incorporation parameters. Cuphen antiproliferative properties were preserved after association to liposomes and IONPs (at 2 mg/mL) did not interfere on cellular proliferation of murine and human melanoma cell lines. Moreover, the developed nanoformulations displayed magnetic properties. The absence of hemolytic activity for formulations under study demonstrated their safety for parenteral administration. In conclusion, a lipid-based nanosystem loading the cytotoxic metallodrug, Cuphen, and displaying magnetic properties was successfully designed. [ABSTRACT FROM AUTHOR]

Magnetic iron oxides have been used in biomedical applications, such as contrast agents for magnetic resonance imaging, carriers for controlled drug delivery and immunoassays, or magnetic hyperthermia for the past 40 years. Our aim is to investigate the effect of pressure and temperature on the structural, thermal, and magnetic properties of iron oxides prepared by hydrothermal synthesis at temperatures of 100–200 °C and pressures of 20–1000 bar. It has been found that pressure influences the type of iron oxide crystalline phase. Thus, the results obtained by Mössbauer characterization are in excellent agreement with X-ray diffraction and optical microscopy characterization, showing that, for lower pressure values (<100 bar), hematite is formed, while, at pressures >100 bar, the major crystalline phase is goethite. In addition, thermal analysis results are consistent with particle size analysis by X-ray diffraction, confirming the crystallization of the synthesized iron oxides. One order of magnitude higher magnetization has been obtained for sample synthesized at 1000 bar. The same sample provides after annealing treatment, the highest amount of good quality magnetite leading to a magnetization at saturation of 30 emu/g and a coercive field of 1000 Oe at 10 K and 450 Oe at 300 K, convenient for various applications. [ABSTRACT FROM AUTHOR]

Self-assembled peptide hydrogels have emerged in recent years as the new paradigm in biomaterials research. We have contributed to this field the development of hydrogels based on dehydrodipeptides N-capped with naproxen. The dehydrodipeptide hydrogels can be loaded with drugs, thus being potential nanocarriers for drug delivery. In this work novel dehydrodipeptides containing tyrosine and aspartic acid amino acid residues N-capped with naproxen and C-terminal dehydrophenylalanine were prepared and characterized. Superparamagnetic iron oxide nanoparticles (SPIONs) were incorporated into the dehydrodipeptide-based hydrogels and their effect on the self-assembly, structure and rheological and magnetic properties of the hydrogels was studied. Magnetic hydrogels, with incorporated SPIONs, displayed concentration-dependent T2-MRI contrast enhancement. Moreover, upon magnetic excitation (alternating magnetic field –AMF–) the SPIONs were able to generate a significant amount of heat. Hence, magnetic hyperthermia can be used as a remote trigger for release of drug cargos and SPIONs incorporated into the self-assembled dehydrodipeptide hydrogels. [ABSTRACT FROM AUTHOR]