Field-Induced Agglomerations of Polyethylene-Glycol-Functionalized Nanoclusters: Rheological Behaviour and Optical Microscopy.

This research aims to investigate the agglomeration processes of magnetoresponsive functionalized nanocluster suspensions in a magnetic field, as well as how these structures impact the behaviour of these suspensions in biomedical applications. The synthesis, shape, colloidal stability, and magnetic characteristics of PEG-functionalized nanoclusters are described in this paper. Experiments using TEM, XPS, dynamic light scattering (DLS), VSM, and optical microscopy were performed to study chain-like agglomeration production and its influence on colloidal behaviour in physiologically relevant suspensions. The applied magnetic field aligns the magnetic moments of the nanoclusters. It provides an attraction between neighbouring particles, resulting in the formation of chains, linear aggregates, or agglomerates of clusters aligned along the applied field direction. Optical microscopy has been used to observe the creation of these aligned linear formations. The design of chain-like structures can cause considerable changes in the characteristics of ferrofluids, ranging from rheological differences to colloidal stability changes.

Recent Advances in the Development of Drug Delivery Applications of Magnetic Nanomaterials.

With the predicted rise in the incidence of cancer, there is an ever-growing need for new cancer treatment strategies. Recently, magnetic nanoparticles have stood out as promising nanostructures for imaging and drug delivery systems as they possess unique properties. Moreover, magnetic nanomaterials functionalized with other compounds can lead to multicomponent nanoparticles with innovative structures and synergetic performance. The incorporation of chemotherapeutic drugs or RNA in magnetic drug delivery systems represents a promising alternative that can increase efficiency and reduce the side effects of anticancer therapy. This review presents a critical overview of the recent literature concerning the advancements in the field of magnetic nanoparticles used in drug delivery, with a focus on their classification, characteristics, synthesis and functionalization methods, limitations, and examples of magnetic drug delivery systems incorporating chemotherapeutics or RNA.

Novel Magnetic Composite Materials for Dental Structure Restoration Application.

In general, magnetic nanoparticles are not often used in dental applications due to some limitations of these materials, such as aggregation problems and low mechanical and chemical resistance but also esthetic problems due to their black color. Our research presents the synthesis of novel magnetic dental composite materials based on magnetic nanoparticles, functionalized and properly coated to overcome the limitations of using magnetic nanoparticles in dental applications. The composites were prepared using a preparation flow containing several integrated reaction steps used previously sequentially. An adequate and deep characterization of dental magnetic composites has been carried out in order to demonstrate that each limitation has been successfully overcome. It was proved that each component brings particular benefits in dental interventions: Fe3O4 nanoparticles have biocompatible, non-toxic properties and also antimicrobial effects; the SiO2 layer significantly increases the mechanical strength of the material; and the Ca(OH)2 layer initiates local calcification and significantly improves the color of the dental composite material. Due to magnetic properties, an innovative application approach on the tooth surface can be achieved under an external magnetic field, which, compared to conventional methods, has a major impact on reducing the occurrence of dental caries under filling materials as well as on reducing microfractures.

Anticoagulant Properties of Coated Fe-Pd Ferromagnetic Shape Memory Ribbons.

Shape memory alloys, especially ferromagnetic shape memory alloys, are interesting new materials for the manufacturing of stents. Iron-palladium alloys in particular can be used to manufacture self-expanding temporary stents due to their optimum rate of degradation, which is between that of magnesium and pure iron, two metals commonly used in temporary stent research. In order to avoid blood clotting upon the introduction of the stent, they are often coated with anticoagulants. In this study, sulfated pectin, a heparin mimetic, was synthesized in different ways and used as coating on multiple iron-palladium alloys. The static and dynamic prothrombin time (PT) and activated partial thromboplastin time (APTT) of the prepared materials were compared to samples uncoated or coated with polyethylene glycol. While no large differences were observed in the prothrombin time measurements, the activated partial thromboplastin time increased significantly with all alloys coated with sulfated pectin. Aside from that, sulfated pectin synthesized by different methods also caused slight changes in the activated partial thromboplastin time. These findings show that iron-palladium alloys can be coated with anticoagulants to improve their utility as material for temporary stents. Sulfated pectin was characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy, and the coated alloys by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Magnetoresponsive Functionalized Nanocomposite Aggregation Kinetics and Chain Formation at the Targeted Site during Magnetic Targeting.

Drug therapy for vascular disease has been promoted to inhibit angiogenesis in atherosclerotic plaques and prevent restenosis following surgical intervention. This paper investigates the arterial depositions and distribution of PEG-functionalized magnetic nanocomposite clusters (PEG_MNCs) following local delivery in a stented artery model in a uniform magnetic field produced by a regionally positioned external permanent magnet; also, the PEG_MNCs aggregation or chain formation in and around the implanted stent. The central concept is to employ one external permanent magnet system, which produces enough magnetic field to magnetize and guide the magnetic nanoclusters in the stented artery region. At room temperature (25 °C), optical microscopy of the suspension model's aggregation process was carried out in the external magnetic field. According to the optical microscopy pictures, the PEG_MNC particles form long linear aggregates due to dipolar magnetic interactions when there is an external magnetic field. During magnetic particle targeting, 20 mL of the model suspensions are injected (at a constant flow rate of 39.6 mL/min for the period of 30 s) by the syringe pump in the mean flow (flow velocity is Um = 0.25 m/s, corresponding to the Reynolds number of Re = 232) into the stented artery model. The PEG_MNC clusters are attracted by the magnetic forces (generated by the permanent external magnet) and captured around the stent struts and the bottom artery wall before and inside the implanted stent. The colloidal interaction among the MNC clusters was investigated by calculating the electrostatic repulsion, van der Waals and magnetic dipole-dipole energies. The current work offers essential details about PEG_MNCs aggregation and chain structure development in the presence of an external magnetic field and the process underlying this structure formation.

High performance magnetorheological fluids: very high magnetization FeCo-Fe3O4 nanoclusters in a ferrofluid carrier.

High magnetization Fe3O4/OA-FeCo/Al2O3 nanocomposite magnetic clusters have been obtained using a modified oil-in-water miniemulsion method. These nanocomposite clusters dispersed in a ferrofluid carrier result in a magnetorheological fluid with improved characteristics. The magnetic clusters have a magnetic core consisting of a mixture of magnetite nanoparticles of about 6 nm average size, stabilized with oleic acid (Fe3O4/OA) and FeCo/Al2O3 particles of about 50 nm average size, compactly packed in the form of spherical clusters with a diameter distribution in the range 100-300 nm and a hydrophilic coating of sodium lauryl sulphate surfactant. The surface chemical composition of the Fe3O4/OA-FeCo/Al2O3 clusters investigated by XPS indicates the presence of the Co2+ and Co3+ oxidation states of cobalt and the components of Fe2+ and Fe3+ characteristic to both an enhanced oxidation state at the surface of the FeCo particles and to the presence of magnetic nanoparticles of spinel structure which are decorating the supporting FeCo. This specific decorating morphology is also indicated by TEM images. Advanced characterization of the Fe3O4/OA-FeCo/Al2O3 magnetic clusters has been performed using Mössbauer spectroscopy and magnetization measurements at various temperatures between 6 K and 200 K. The unexpected formation of Co ferrite decorating nanoparticles was supported by Mössbauer spectroscopy. The dispersion of magnetic clusters in the ferrofluid carrier highly influences the flow properties in the absence of the field (shear thinning for low and moderate shear rates) and especially in applied magnetic field, when significant magnetoviscous effect and shear thinning was observed for the whole range of shear rate values. Detailed analysis of the magnetorheological behavior of the nanocomposite magnetic clusters dispersed in a ferrofluid carrier evidence significantly higher normalized dynamic yield stress values in comparison with the magnetite nanocluster suspensions of the same mass concentration, a promising result for this new type of nanocomposite magnetorheological fluid.

In Vivo Distribution of Poly(ethylene glycol) Functionalized Iron Oxide Nanoclusters: An Ultrastructural Study.

The in vivo distribution of 50 nm clusters of polyethylene glycol-conjugated superparamagnetic iron oxide nanoparticles (SPIONs-PEG) was conducted in this study. SPIONs-PEG were synthesized de novo, and their structure and paramagnetic behaviors were analyzed by specific methods (TEM, DLS, XRD, VSM). Wistar rats were treated with 10 mg Fe/kg body weight SPIONs-PEG and their organs and blood were examined at two intervals for short-term (15, 30, 60, 180 min) and long-term (6, 12, 24 h) exposure evaluation. Most exposed organs were investigated through light and transmission electron microscopy, and blood and urine samples were examined through fluorescence spectrophotometry. SPIONs-PEG clusters entered the bloodstream after intraperitoneal and intravenous administrations and ended up in the urine, with the highest clearance at 12 h. The skin and spleen were within normal histological parameters, while the liver, kidney, brain, and lungs showed signs of transient local anoxia or other transient pathological affections. This study shows that once internalized, the synthesized SPIONs-PEG disperse well through the bloodstream with minor to nil induced tissue damage, are biocompatible, have good clearance, and are suited for biomedical applications.

Dental Adhesive Interfaces Reinforced with Magnetic Nanoparticles: Evaluation and Modeling with Micro-CT versus Optical Microscopy.

Dental adhesives are used in a wide range of applications, including to place direct composite restorations in frontal or posterior teeth. One of the most frequent causes for the failure of composite resin restorations is microleakages. The first aim of this work is to introduce a new type of self-etched dental adhesive doped with magnetic nanoparticles (MPs) synthetized in the laboratory. The scope is to produce adhesives with a minimized width/thickness to decrease the risk of microleakages. The second aim is to assess the width/thickness of the adhesive layer in all the characteristic areas of the teeth using both the less precise but most common optical microscopy and the more accurate and volumetric micro-Computed Tomography (CT) investigations. Twenty extracted teeth have been divided into four groups: Group 1 includes 'blank' samples with adhesives that are not doped with MPs; Group 2 includes samples with adhesives doped with MPs; Groups 3 and 4 include samples with adhesives doped with MPs that are subjected to an active magnetic field for 5 and 10 min, respectively. Microscopy investigations followed by micro-CT and EDAX are performed on the adhesive. While a rather good agreement is obtained between the microscopy and micro-CT results, the capability of the latter to offer a full volumetric reconstruction of the layer is exploited to analyze the adhesion of the four considered dental materials. Thus, from micro-CT results the graphs of the surface areas as functions of the adhesive layer width are modeled mathematically, as well as the volume of sealants, for each of the four groups. To our knowledge, it is the first time that such a methodology is used. Characteristic parameters are extracted and the ascertainment of the optimal parameter that should be utilized for such assessments is discussed. The study demonstrates the adhesion improvement produced for Groups 3 and 4, where MPs are used. It also concludes that the magnetic field should be applied to the adhesive material for the longest possible exposure time (with a trade-off with the clinical duration of the treatment).

Magnetic microgels, a promising candidate for enhanced magnetic adsorbent particles in bioseparation: synthesis, physicochemical characterization, and separation performance.

For specific applications in the field of high gradient magnetic separation of biomaterials, magnetic nanoparticle clusters of controlled size and high magnetic moment in an external magnetic field are of particular interest. We report the synthesis and characterization of magnetic microgels designed for magnetic separation purposes, as well as the separation efficiency of the obtained microgel particles. High magnetization magnetic microgels with superparamagnetic behaviour were obtained in a two-step synthesis procedure by a miniemulsion technique using highly stable ferrofluid on a volatile nonpolar carrier. Spherical clusters of closely packed hydrophobic oleic acid-coated magnetite nanoparticles were coated with cross linked polymer shells of polyacrylic acid, poly-N-isopropylacrylamide, and poly-3-acrylamidopropyl trimethylammonium chloride. The morphology, size distribution, chemical surface composition, and magnetic properties of the magnetic microgels were determined using transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Magnetically induced phase condensation in aqueous suspensions of magnetic microgels was investigated by optical microscopy and static light scattering. The condensed phase consists of elongated oblong structures oriented in the direction of the external magnetic field and may grow up to several microns in thickness and tens or even hundreds of microns in length. The dependence of phase condensation magnetic supersaturation on the magnetic field intensity was determined. The experiments using high gradient magnetic separation show high values of separation efficiency (99.9-99.97%) for the magnetic microgels.