Magnetic Nanoparticles Loading Research Articles

Spatially Confined Assembly and Immobilization of Hierarchical Nanoparticle Architectures inside Microdroplets in Magnetic Fields.

Magnetic field-directed colloidal interactions offer facile tools for assembly of structures that range from linear chains to multidimensional hierarchical architectures. While the field-driven assembly of colloidal particles has commonly been investigated in unbounded media, a knowledge gap remains concerning such assembly in confined microenvironments. Here, we investigate how confinement of ferromagnetic nanoparticles in microspheres directs their magnetic assembly into hierarchical architectures. Microdroplets from polydimethylsiloxane (PDMS) liquid precursor containing dispersed iron oxide magnetic nanoparticles (MNPs) were placed in a static magnetic field leading to the formation of organized assemblies inside the host droplets. By changing the MNP concentrations, we revealed a sequence of microstructures inside the droplets, ranging from linear chains at a low MNP loading, transitioning to a combination of chains and networked bundles, to solely 3D bundles at high MNP loading. These experimental results were analyzed with the aid of COMSOL simulations where we calculated the potential energy to identify the preferred assembly conformations. The chains at high MNP loading minimized their energy by aggregating laterally to form bundles with their MNP dipoles being out-of-registry. We cured these PDMS droplets to immobilize the assemblies by forming soft microbeads. These microbeads constitute an "interaction toolbox" with different magnetic macroscale responses, which are governed by the structuring of the MNPs and their magnetic polarizability. We show that thanks to their ability to rotate by field-induced torque under a rotating field, these microbeads can be employed in applications such as optical modulators and microrollers.

Magnetic nanoparticle loading and application of weak magnetic field to reconstruct the cake layer of coagulation-ultrafiltration process to achieve efficient antifouling: Performance and mechanism analysis

Abandoning the costly development of new membrane materials and instead directly remodeling the naturally occurring cake layer constitutes a dynamic, low-cost, long-lasting, and proactive strategy to "fight fouling with fouling". Several optimization strategies, including coagulation/modified magnetic seed loading and applying a weak magnetic force (0.01T) at the ultrafiltration end, improved the anti-fouling, retention, and sieving performances of conventional ultrafiltration process during the treatment of source water having complex natural organic matter (NOMs) and small molecule micropollutants. Two modified magnetic seeds we prepared were composite nano-seed particles (Fe3O4@SiO2-NH2 (FS) and Fe3O4@SiO2@PAMAM-NH2 (FSP)). Aim of the study was to regulate the formation of cake layer via comprehensive testing of the antifouling properties of optimized processes and related mechanistic studies. It was found to be essential to enhance the interception of xanthate and tryptophan proteins in the cake layer for improving the anti-fouling performance based on the correlation and redundancy analyses, while the use of modified magnetic seeds and magnetic field showed a significant positive impact on water production. Blockage modeling demonstrated the ability to form a mature cake layer during the initial filtration stage swiftly. This mitigated the risk of irreversible fouling caused by pore blockage during the early stage of coagulation-ultrafiltration. Morphologically, the reconstructed cake layer exhibited elevated surface porosity, an internal cavity channel structure, and enhanced roughness that can promote increased water flux and retention of water impurities. These optimized the maturity of the cake layer in both time and space. Density Functional Theory (DFT), Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and Modified Extended Derjaguin-Landau-Verwey-Overbeek (MDLVO) calculations indicated aggregation behavior of matter on the cake layer to be enhanced effectively due to magnetic seed loading. This is mainly due to the strengthening of polar interactions, including hydrogen bonding, π-π* conjugation, etc., which can happen between the cake layer loaded with FSP and the organic matter. Under the influence of a magnetic field, magnetic force energy (VMF) significantly impacts the system by eliminating energy barriers. This research will provide innovative strategies for effectively purifying intricate source water through ultrafiltration while controlling membrane fouling.

Synergistic naproxen adsorption and peroxymonosulfate-driven oxidation on defective magnetic porous graphene dual functional materials

In this study, recycled and highly active magnetic porous graphene (MPG) was prepared through defect treatment of graphene-based materials and the loading of magnetic nanoparticles. A coupling technology of adsorption and peroxymonosulfate advanced oxidation was established to remove Naproxen (NPX) from water by utilizing the excellent defect structure and abundant active sites of MPG. The removal efficiency of NPX using the MPG/PMS system was 100% within 120 min, in which the adsorption stage took 30 min and contributed 70.3% to the removal of NPX. Subsequently, the reaction rate constant reached the maximum value of 0.782 min−1 in the first minute of the chemical reaction stage after adding PMS. Quenching and EPR analysis confirmed that both free radicals (O2·-, SO4·- and·OH) and nonfree radicals (1O2) generated in the MPG/PMS system participated in the degradation of NPX. The electrochemical test further confirmed that the generation of nonfree radicals promoted by electron transfer played a major role, and the high chemical reaction active center was exposed due to the internal defects of MPG. The excellent anti-interference and widespread applicability of MPG have been verified. The intermediate products, degradation pathways, and toxicity changes of NPX degradation were analyzed and summarized.

Assembly of Metal-Phenolic Networks onto Microbubbles for One-Step Generation of Functional Microcapsules.

The one-step assembly of metal-phenolic networks (MPNs) onto particle templates can enable the facile, rapid, and robust construction of hollow microcapsules. However, the required template removal step may affect the refilling of functional species in the hollow interior space or the in situ encapsulation of guest molecules during the formation of the shells. Herein, a simple strategy for the one-step generation of functional MPNs microcapsules is proposed. This method uses bovine serum albumin microbubbles (BSA MBs) as soft templates and carriers, enabling the efficient pre-encapsulation of guest species by leveraging the coordination assembly of tannic acid (TA) and FeIII ions. The addition of TA and FeIII induces a change in the protein conformation of BSA MBs and produces semipermeable capsule shells, which allow gas to escape from the MBs without template removal. The MBs-templated strategy can produce highly biocompatible capsules with controllable structure and size, and it is applicable to produce other MPNs systems like BSA-TA-CuII and BSA-TA-NiII . Finally, those MBs-templated MPNs capsules can be further functionalized or modified for the loading of magnetic nanoparticles and the pre-encapsulation of model molecules through covalence or physical adsorption, exhibiting great promise in biomedical applications.

Electrospun superparamagnetic fibrous composite nanofiber films for enhanced oil spill recovery: Effect of capping and magnetic nanoparticle loading on oil sorption efficiency

Electrospun superparamagnetic fibrous composite nanofiber films for enhanced oil spill recovery: Effect of capping and magnetic nanoparticle loading on oil sorption efficiency

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions.

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe3O4 nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Combined Ferromagnetic Nanoparticles for Effective Periodontal Biofilm Eradication in Rat Model.

The critical challenge for periodontitis therapy is thoroughly eliminating the dental plaque biofilm, particularly penetrating the deep periodontal tissue. Regular therapeutic strategies are insufficient to penetrate the plaque without disturbing the commensal microflora of the oral cavity. Here, we constructed a Fe3O4 magnetic nanoparticle loading minocycline (FPM NPs) to penetrate the biofilm physically and effectively eliminate periodontal biofilm. In order to penetrate and remove the biofilm effectively, Fe3O4 magnetic nanoparticles were modified with minocycline using a co-precipitation method. The particle size and dispersion of the nanoparticles were characterized by transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. The antibacterial effects were examined to verify the magnetic targeting of FPM NPs. Confocal laser scanning microscopy was employed to check the effect of FPM + MF and develop the best FPM NPs treatment strategy. Additionally, the therapeutic effect of FPM NPs was investigated in periodontitis rat models. The expression of IL-1β, IL-6, and TNF-α in periodontal tissues was measured by qRT-PCR and Western blot. The multifunctional nanoparticles exhibited intense anti-biofilm activity and good biocompatibility. The magnetic forces could pull FMP NPs against the biofilm mass and kill bacteria deep in the biofilms both in vivo and in vitro. The integrity of the bacterial biofilm is disrupted under the motivation of the magnetic field, allowing for improved drug penetration and antibacterial performance. The periodontal inflammation recovered well after FPM NPs treatment in rat models. Furthermore, FPM NPs could be monitored in real-time and have magnetic targeting potentials. FPM NPs exhibit good chemical stability and biocompatibility. The novel nanoparticle presents a new approach for treating periodontitis and provides experimental support for using magnetic-targeted nanoparticles in clinic applications.

Advanced micro-/nanotechnologies for exosome encapsulation and targeting in regenerative medicine.

Exosomes, a subset of vesicles generated from cell membranes, are crucial for cellular communication. Exosomes' innate qualities have been used in recent studies to create nanocarriers for various purposes, including medication delivery and immunotherapy. As a result, a wide range of approaches has been designed to utilize their non-immunogenic nature, drug-loading capacity, or targeting ability. In this study, we aimed to review the novel methods and approaches in exosome engineering for encapsulation and targeting in regenerative medicine. We have assessed and evaluated each method's efficacy, advantages, and disadvantages and discussed the results of related studies. Even though the therapeutic role of non-allogenic exosomes has been demonstrated in several studies, their application has certain limitations as these particles are neither fully specific to target tissue nor tissue retainable. Hence, there is a strong demand for developing more efficient encapsulation methods along with more accurate and precise targeting methods, such as 3D printing and magnetic nanoparticle loading in exosomes, respectively.

Facile fabrication of 3D biochar absorbers dual-loaded with Fe3O4 nanoparticles for enhanced microwave absorption

Biochar microwave absorption (MA) materials are attracting significant attention due to their sustainability and cost-effective features. To endow them with enhanced MA performance, surface loading of magnetic nanoparticles (NPs) based on biotemplates is becoming a valid strategy. However, realizing hybrid deposition of magnetic NPs onto surfaces and internal spaces of the biotemplates still remains a big challenge for effective absorption. Herein, we proposed a novel biochar absorber based on Spirulina (SP) cells dual-loaded with Fe3O4 NPs and demonstrated their enhanced performance for MA. In this approach, the SP cells were permeabilized and deposited with Fe3O4 NPs both extracellularly and intracellularly, to obtain the precursors (Fe3O4@SPs). Then, annealing treatment was conducted at various temperatures (X °C) to fabricate the biochar absorbers (Fe3O4@SP-BCs-X). The Fe3O4@SP-BCs-700 composites exhibited the best MA performance among the samples, and the minimum reflection loss (RLmin) could attain −45.54 dB at 14.68 GHz (thickness: 1.49 mm, mass ratio in paraffin: 18.6 wt%). Moreover, the biochar absorbers with hybrid deposition could achieve enhanced absorption compared to the samples with single deposition. Due to these superior features and facile fabrication, the Fe3O4@SP-BCs demonstrated great potential for MA applications.

Cell Tracking by Magnetic Particle Imaging: Methodology for Labeling THP-1 Monocytes with Magnetic Nanoparticles for Cellular Imaging.

Magnetic particle imaging (MPI) is a noninvasive tomographic imaging modality for the quantitative visualization of magnetic nanoparticles (MNPs) with high temporal and spatial resolution. The general capability of MPI for cell tracking (e.g., monitoring living cells labeled with MNPs) has successfully been shown. MNPs in cell culture media are often subjected to structural and magnetic changes. In addition to the deteriorating reproducibility, this also complicates the systematic study of the relationship between the MNP properties and their cellular uptake for MPI. Here, we present a method for the preparation of magnetically labeled THP-1 (Tamm–Horsfall Protein-1) monocytes that are used in MPI cell tracking. The method development was performed using two different MPI tracers, which exhibited electrostatic and steric stabilizations, respectively. In the first step, the interaction between the MNPs and cell culture media was investigated and adjusted to ensure high structural and magnetic stability. Furthermore, the influences of the incubation time, MNP concentration used for cellular uptake, and individual preparation steps (e.g., the washing of cells) were systematically investigated. Finally, the success of the developed loading method was demonstrated by the MPI measurements. The presented systematic investigation of the factors that influence the MNP loading of cells will help to develop a reliable and reproducible method for MPI monocyte tracking for the early detection of inflammation in the future.

Dual-Responsive multifunctional “core–shell” magnetic nanoparticles promoting Fenton reaction for tumor ferroptosis therapy

Ferroptosis is a newly found promising cell death pathway, which bypasses apoptosis and overcomes multidrug resistance of tumor. In this study, acid and redox dual-responsive multifunctional magnetic nanoparticles loading with Sorafenib (Sor), namely FMMHG/Sor, were prepared for tumor ferroptosis therapy. Fe3O4 nanoparticles as the core provided sufficient iron ion for ferroptosis and magnetic targeting. Mesoporous organosilica nanoparticles (MON) was coated on the outside of Fe3O4 to form “core–shell” structure, which contained the disulfidebond with redox-responsive. MnO2 was dropped on the surface of MON as gatekeeper, which was decomposed at low pH into O2 to promote drug release. Glucose oxidase (GOD) catalyzed glucose to produce H2O2, which reacted with iron ion to generate hydroxylradical (OH•) vie Fenton reaction. OH• inhibited GPX4 expression to induce ferroptosis with Sor as a synergistic inducer. Hyaluronic acid (HA) protected nanoparticles from removed by immune system and actively targeted to tumor cells. Overall, pH and redox dual-responsive FMMHG/Sor is a promising antitumor nanomedicine with magnetic targeting and active targeting for efficient tumor ferroptosis therapy.

Multifunctional nanostructured drug delivery carriers for cancer therapy: Multimodal imaging and ultrasound-induced drug release

Development of multimodal systems for therapy and diagnosis of neoplastic diseases is an unmet need in oncology. The possibility of simultaneous diagnostics, monitoring, and therapy of various diseases allows expanding the applicability of modern systems for drug delivery. We have developed hybrid particles based on biocompatible polymers containing magnetic nanoparticles (MNPs), photoacoustic (MNPs), fluorescent (Cy5 or Cy7 dyes), and therapeutic components (doxorubicin). To achieve high loading efficiency of MNP and Dox to nanostructured carriers, we utilized a novel freezing-induced loading technique. To reduce the systemic toxicity of antitumor drugs and increase their therapeutic efficacy, we can use targeted delivery followed by the remote control of drug release using high intensity-focused ultrasound (HIFU). Loading of MNPs allowed performing magnetic targeting of the carriers and enhanced optoacoustic signal after controlled destruction of the shell and release of therapeutics as well as MRI imaging. The raster scanning optoacoustic mesoscopy (PA, RSOM), MRI, and fluorescent tomography (FT) confirmed the ultrasound-induced release of doxorubicin from capsules: in vitro (in tubes and pieces of meat) and in vivo (after delivery to the liver). Disruption of capsules results in a significant increase of doxorubicin and Cy7 fluorescence initially quenched by magnetite nanoparticles that can be used for real-time monitoring of drug release in vivo. In addition, we explicitly studied cytotoxicity, intracellular localization, and biodistribution of these particles. Elaborated drug delivery carriers have a good perspective for simultaneous imaging and focal therapy of different cancer types, including liver cancer.

All-screen-printed graphite sensors integrating permanent bonded magnets. Fabrication, characterization and analytical utility

Electrochemical magneto assays have been extremely popular thanks to the facile manipulation of magnetic nanoparticles (MNPs) by a magnetic field. To this end, various related accessories, such as magnetic electrode shafts, electrochemical cells integrating (electro)magnets, magnetic stickers etc. have been developed aiming to attract MNPs on the electrode surface. Herein, we introduce for the first time screen-printed electrodes (SPEs) coupled with screen-printed permanent bonded magnets as a compact, portable, cheap and disposable alternative to aforementioned products. The bonded magnet (3 mm ∅, 56 ± 6 μm thick) consists of micro sized NdFeB particles dispersed in a thixotropic ink, and it was printed on a 100 μm thick polyester film, aligned with the electroactive surface of the SPE, which is printed on the other side of the substrate. Various parameters, such as the composition of the NdFeB/ink blend, the thickness and the pattern (compact or hole-engraved) of the printed magnet, and the thickness of the substrate were investigated by both experimental and theoretical studies. After the magnetization of the bonded magnet with a vibrating sample magnetometer at 2 T, a sufficient magnetic field strength was obtained. The performance is enhanced if a void round area is created in the center of the magnet to introduce a further area of strong field gradient. This pattern allows the development of stronger attracting forces to MNPs, higher MNPs loading and a better distribution of them on the electrode surface. The effective electron transfer between Fe3O4 MNPs and the electrode surface is shown with the electrochemical conversion of surface confined Fe3O4 MNPs to Prussian blue electroactive moieties and the amperometric determination of hydrogen peroxide, while the ultrasensitive determination of riboflavin using Ag/Fe3O4 MNP modified magnet-SPEs is demonstrated.

Dihydroartemisinin-Loaded Magnetic Nanoparticles for Enhanced Chemodynamic Therapy.

Recently, chemodynamic therapy (CDT) has represented a new approach for cancer treatment with low toxicity and side effects. Nonetheless, it has been a challenge to improve the therapeutic effect through increasing the amount of reactive oxygen species (ROS). Herein, we increased the amount of ROS agents in the Fenton-like reaction by loading dihydroartemisinin (DHA) which was an artemisinin (ART) derivative containing peroxide groups, into magnetic nanoparticles (MNP), thereby improving the therapeutic effect of CDT. Blank MNP were almost non-cytotoxic, whereas three MNP loading ART-based drugs, MNP-ART, MNP-DHA, and MNP-artesunate (MNP-AS), all showed significant killing effect on breast cancer cells (MCF-7 cells), in which MNP-DHA were the most potent. What’s more, the MNP-DHA showed high toxicity to drug-resistant breast cancer cells (MCF-7/ADR cells), demonstrating its ability to overcome multidrug resistance (MDR). The study revealed that MNP could produce ferrous ions under the acidic condition of tumor microenvironment, which catalyzed DHA to produce large amounts of ROS, leading to cell death. Further experiments also showed that the MNP-DHA had significant inhibitory effect on another two aggressive breast cancer cell lines (MDA-MB-231 and MDA-MB-453 cells), which indicated that the great potential of MNP-DHA for the treatment of intractable breast cancers.

Magnetic tubular carbon nanofibers as efficient Cu(II) ion adsorbent from wastewater

Abstract Novel magnetic tubular carbon nanofibers (MTCFs) were prepared from hypercrosslinked α, ά-dichloro-p-xylene as a green adsorbent for efficient Cu(II) ion removal from the wastewater. The new route involving the following steps, such as dual oil phase polymerization, carboxyl functionalization and loading of magnetic nanoparticles (Fe3O4) was developed. The surface area, saturation magnetization, inner and outer diameters of MTCFs are 280.94 m2/g, 10.65 emu/g, 25 nm and 110 nm. The adsorption properties were studied by batch methods. The highest removal efficiency for Cu(II) ion was achieved 99.9 ± 0.1% in a short contact time 10 min and a small amount of MTCFs dosage 0.5 g/L with pH = 6. From kinetic studies, the Pseudo first order kinetic model was best fitted with experimental data than the Pseudo second order. From isothermal studies, the Langmuir model was best fixed with the highest R2 in contrast to the Freundlich isotherm model. The highest adsorption for Cu(II) ion 375.93 mg/g was achieved from the Langmuir isotherm. The parameters determined from thermodynamics ΔGᵒ, ΔHᵒ, ΔSᵒ confirmed Cu(II) ion adsorption was spontaneous, thermodynamically it was endothermic and random adsorption process. Regeneration and reuse of MTCFs up to six cycles with the same contact for all adsorption cycles.

Rapid 3D Printing Magnetically Active Microstructures with High Solid Loading

The capability of fabricating magnetically active 3D microstructures is crucial for miniaturization of microrobots or microactuators. While additive manufacturing using magnetic nanoparticle‐infused polymer resin offers the highly desirable precision and flexibility, the difficulty in handling resin with higher solid loading of magnetic nanoparticles needed to maximize the magnetic actuation forces remains to be the main obstacle. The increased viscosity of the magnetic resin not only significantly reduces the fabrication speed, but also makes the process vulnerable to the precipitation of the suspended magnetic nanoparticles. Herein, a comprehensive solution that synergizes the optimization of magnetic photopolymerizable resin and the high‐speed 3D printing using microcontinuous liquid interface production (μCLIP) process is reported. An optimized magnetic photopolymerizable resin with 30 wt% solid loading of Fe3O4 nanoparticles is well dispersed over 72 h. Process characteristics of the magnetic photopolymerizable resins with variation in the solid loading of magnetic nanoparticles are investigated experimentally. The capability of 3D printing centimeter‐size samples with sub‐75 μm fine features using high solid loading (30 wt%) is also demonstrated. The increased printing speed using μCLIP significantly reduces the fabrication time to the order of minutes to hours, making the process more robust against the precipitation of the magnetic particles.

A novel electroconductive interface based on Fe3 O4 magnetic nanoparticle and cysteamine functionalized AuNPs: Preparation and application as signal amplification element to minoring of antigen-antibody immunocomplex and biosensing of prostate cancer.

In this study, a novel electroconductive interface was prepared based on Fe3 O4 magnetic nanoparticle and cysteamine functionalized gold nanoparticle. The engineered interface was used as signal amplification substrate in the electrochemical analysis of antibody-antigen binding. For this purpose, biotinilated-anti-prostate-specific antigen (PSA) antibody was bioconjugated with iron oxide magnetic nanoparticles (Fe3 O4 ) and drop-casted on the surface of glassy carbon electrode (GCE). Also, secondary antibody (HRP-Ab2) encapsulated on gold nanoparticles caped by cysteamine was immobilized on the surface of GCE modified electrode. A transmission electron microscopy images shows that a sandwich immunoreaction was done and binding of Ab1 and Ab2 performed successfully. Various parameters of immunoassay, including the loading of magnetic nanoparticles, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.001 μg. L-1 of PSA was obtained under optimum experimental conditions. It is found that such magneto-bioassay could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for early stage diagnosis of cancer in near future.

Magnetic/Gold Core-Shell Hybrid Particles for Targeting and Imaging-Guided Photothermal Cancer Therapy.

The development of hybrid particles for tumor diagnosis and therapy has received considerable attention because they are capable of combining tumor diagnosis and treatment concurrently. So far hybrid particles for efficient and safe tumor theranostics are still very limited. Herein we have designed a new type of hybrid particles and evaluated its potential to be used in image-guided cancer diagnosis and therapy without the need of any toxic anticancer or contrast agents. The hybrid particles, consist of magnetic nanoparticles which are embedded in the poly(methyl methacrylate) (PMMA) cores and gold shells on chitosan (CTS) (γ-Fe₂O₃ @PMMA/CTS@Au). The hybrid particles were synthesized through initial formation of the core-shell structured γ-Fe₂O₃ @PMMA/CTS particles containing approximately 20% loading of magnetic nanoparticles. A gold layer was then built on top of the core-shell magnetic particles via a reduction of gold salt by amines from the chitosan assisted with the reducing agent NaBH₄, followed by growing to complete gold shells in the presence of ascorbic acid (42.6% Au content). The properties of the composite particles including their chemical composition, morphology, particle size, size distribution, surface charge, magnetic responsiveness and photothermal ability were systematically characterized. The potential application of the γ-Fe₂O₃ @PMMA/CTS@Au hybrid particles in tumor diagnosis and therapy was assessed in vitro and in vivo using 4T1 tumor cells and 4T1 tumor-bearing mice through combining magnetic targeting, photoacoustic (PA)/computed tomography (CT) imaging and photothermal therapy. Results suggest that the γ-Fe₂O₃ @PMMA/CTS@Au particles can serve as a multifunctional tumor theranostic nanoplatform for magnetically targeted photothermal therapy. Breast cancer has been effectively eliminated without the use of any anticancer drugs or contrast agents. Therefore, this type of core-shell hybrid particles represents a new composite particle design for effective and safe tumor theranostics.

Printed Thin Diblock Copolymer Films with Dense Magnetic Nanostructure

Thin hybrid films with dense magnetic structures for sensor applications are printed using diblock copolymer (DBC) templating magnetic nanoparticles (MNPs). To achieve a high-density magnetic structure, the printing ink is prepared by mixing polystyrene- block-poly(methyl methacrylate) (PS- b-PMMA) with a large PS volume fraction and PS selective MNPs. Solvent vapor annealing is applied to generate a parallel cylindrical film morphology (with respect to the substrate), in which the MNP-residing PS domains are well separated by the PMMA matrix, and thus, the formation of large MNP agglomerates is avoided. Moreover, the morphologies of the printed thin films are determined as a function of the MNP concentration with real and reciprocal space characterization techniques. The PS domains are found to be saturated with MNPs at 1 wt %, at which the structural order of the hybrid films reaches a maximum within the studied range of MNP concentration. As a beneficial aspect, the MNP loading improves the morphological order of the thin DBC films. The dense magnetic structure endows the thin films with a faster superparamagnetic responsive behavior, as compared to thick films where identical MNPs are used, but dispersed inside the minority domains of the DBC.

Effect of initial susceptibility and relaxation dynamics on radio frequency alternating magnetic field induced heating in superparamagnetic nanoparticle dispersions

Radiofrequency alternating magnetic field (RFAMF) induced heating of superparamagnetic nanoparticle dispersions (magnetic nanofluids) have attracted wide attention due to its superior potential for various industrial and bio-medical applications. Here, we probe the role of initial susceptibility and relaxation dynamics on RFAMF induced heating efficiency of magnetic nanofluids containing oleic acid capped single domain Fe3O4 magnetic nanoparticles (MNP) with nearly similar saturation magnetization values. Our results suggest that the initial susceptibility of MNP plays a major role in RFAMF induced heating efficiency and the variation of MNP size dependant relaxation dynamics alone is not sufficient to account for the field induced heating efficiency. Calculations on quasi-static hysteresis loops revealed a decrease in initial susceptibility with increasing MNP loading due to enhanced dipolar interaction, which resulted in the observed decrease in heating efficiency with increasing MNP concentration. The effect of relaxation dynamics on SAR, probed by varying the base fluid viscosity, showed that the heating efficiency is largely unaffected with increasing medium viscosity for magnetic nanofluids with Neel dominated relaxation modes, whereas heating efficiency decreased by ∼70% for magnetic nanofluids with Brownian dominant relaxation modes. This study attempts to decouple the individual contributions of initial susceptibility and relaxation dynamics and the results obtained are beneficial for designing magnetic nanofluids with enhanced magneto-thermal conversion efficiency.