Optimization of Magnetic Tunnel Junction Structure through Component Analysis and Deposition Parameters Adjustment.

In this work, we focus on a detailed study of the role of each component layer in the multilayer structure of a magnetic tunnel junction (MTJ) as well as the analysis of the effects that the deposition parameters of the thin films have on the performance of the structure. Various techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the effects of deposition parameters on the surface roughness and thickness of individual layers within the MTJ structure. Furthermore, this study investigates the influence of thin films thickness on the magnetoresistive properties of the MTJ structure, focusing on the free ferromagnetic layer and the barrier layer (MgO). Through systematic analysis and optimization of the deposition parameters, this study demonstrates a significant improvement in the tunnel magnetoresistance (TMR) of the MTJ structure of 10% on average, highlighting the importance of precise control over thin films properties for enhancing device performance.

High Catalytic Activity of CoxPt100-x Alloys for Phenolic Compound Reduction.

In this study, we report the influence of the Pt concentration in CoxPt100-x alloys on the catalytic activity of the alloys for 4-nitrophenol (4-NP) reduction. More precisely, a series of CoxPt100-x alloys with a Pt concentration ranging between 60% and 95% were prepared using electrodeposition at controlled potentials from stable hexachloroplatinate aqueous solution. The Pt concentration was tuned by varying the electrodeposition potential from -0.6 to -0.9 V. The changes in the CoxPt100-x alloy microstructure and crystalline structure have been investigated using SEM and TEM analysis. Our results show that the microstructure and the crystalline structure of the as-prepared materials do not depend on the electrodeposition potential. However, the catalytic activity of CoxPt100-x alloys is closely correlated with the potential applied during electrochemical synthesis, hence the Pt content. We demonstrated that the synthesized materials present a high catalytic activity (approx. 90%) after six cycles of reusability despite the fact that the Pt content of the as-prepared alloys decreases. The easy preparation method that guarantees more than 97% catalytic activity of the CoxPt100-x alloys, the easy recovery from solution, and the possibility of reusing the CoxPt100-x alloys are the benefits of the present study.

Fe-Cr-Nb-B Magnetic Particles and Adipose-Derived Mesenchymal Cells Trigger Cancer Cell Apoptosis by Magneto-Mechanical Actuation.

Magnetic nanoparticles (MPs) are emerging as powerful and versatile tools for biotechnology, including cancer research and theranostic applications. Stem cell-mediated magnetic particle delivery has been previously recognized as a modality to target sites of malignancies. Here, we propose the use of adipose-derived mesenchymal cells (ADSC) for the targeted delivery of Fe-Cr-Nb-B magnetic particles to human osteosarcoma (HOS) cells and magneto-mechanical actuation (MMA) for targeting and destroying HOS cells. We show that MPs are easily incorporated by ADSCs and HOS cells, as confirmed by TEM images and a ferrozine assay. MP-loaded ADSCs display increased motility towards tumor cells compared with their unloaded counterparts. MMA of MP-loaded ADSCs induces HOS destruction, as confirmed by the MTT and live/dead assays. MMA enables the release of the MPs towards cancer cells, producing a significant decrease (about 80%) in HOS viability immediately after application. In contrast, normal human dermal fibroblasts' (NHDFs) viability exposed to similar conditions remains high, showing a differential behavior of normal and malignant cells to MP load and MMA exposure. Taken together, the method could derive successful strategies for in vivo applications in targeting and destroying malignant cells while protecting normal cells.

Magnetic nanoparticle loaded human adipose derived mesenchymal cells spheroids in levitated culture.

Magnetic nanoparticles (MNP) are intensely scrutinized for biomedical applications due to their excellent biocompatibility and adjustable magnetic field (MF) responsiveness. Three-dimensional spheroid culture of ADSC improves stem cell proliferation and differentiation, increasing their potential for clinical applications. In this study we aimed to detect if MF levitated culture of ADSC loaded with proprietary MNP maintain the properties of ADSC and improve their performances. Levitated ADSC-MNP formed aggregates with increased volume and reduced number compared to nonlevitated ones. ADSC-MNP from levitated spheroid displayed higher viability, proliferation and mobility compared to nonlevitated and 2D culture. Levitated and nonlevitated ADSC-MNP spheroids underwent three lineage differentiation, demonstrating preserved ADSC stemness. Quantitative osteogenesis showed similar values in MNP-loaded levitated and nonlevitated spheroids. Significant increases in adipogenic conversion was observed for all 3D formulation. Chondrogenic conversion in levitated and nonlevitated spheroids produced comparable ratio glucosaminoglycan (GAG)/DNA. Increased chondrogenesis could be observed for ADSC-MNP in both levitated and nonlevitated condition. Taken together, ADSC-MNP levitated spheroids retain stemness and display superior cell viability and migratory capabilities. Furthermore, the method consistently increases spheroid maneuverability, potentially facilitating large scale manufacturing and automation. Levitated spheroid culture of ADSC-MNP can be further tested for various application in regenerative medicine and organ modeling.

Sequential Synthesis Methodology Yielding Well-Defined Porous 75%SrTiO3/25%NiFe2O4 Nanocomposite.

In this research, we reported on the formation of highly porous foam SrTiO3/NiFe2O4 (100-xSTO/xNFO) heterostructure by joint solid-state and sol-gel auto-combustion techniques. The colloidal assembly process is discussed based on the weight ratio x (x = 0, 25, 50, 75, and 100 wt %) of NiFe2O4 in the 100-xSTO/xNFO system. We proposed a mechanism describing the highly porous framework formation involving the self-assembly of SrTiO3 due to the gelation process of the nickel ferrite. We used a series of spectrophotometric techniques, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption isotherms method, UV-visible diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometer (VSM), and dielectric measurements, to investigate the structural, morphological, optical, magnetic, and dielectric properties of the synthesized samples. As revealed by FE-SEM analysis and textural characteristics, SrTiO3-NiFe2O4 nanocomposite self-assembled into a porous foam with an internally well-defined porous structure. HRTEM characterization certifies the distinctive crystalline phases obtained and reveals that SrTiO3 and NiFe2O4 nanoparticles were closely connected. The specific magnetization, coercivity, and permittivity values are higher in the 75STO/25NFO heterostructure and do not decrease proportionally to the amount of non-magnetic SrTiO3 present in the composition of samples.

Flash-cooling assisted sol-gel self-ignited synthesis of magnetic carbon dots-based heterostructure with antitumor properties.

This work addresses current direction of the nanoparticles-based systems intended for cancer therapy by developing a newly-formulated innovative chemically-engineered anti-tumor composite consisting in a magnetic, fluorescent, lipophilic, and biologically-active carbon heterostructure capable by itself or through coupling with a chemotherapeutic agent to selectively induce tumor cell death. The anti-tumor compound was synthesized through a modified sol-gel method by addition of a low-cost molecule with recently proven anti-tumor properties which was combusted and flash-cooled along with magnetic iron oxides precursors at 250 °C. The synthesized compound consisted in carbon dots, graphene and hematite nanoparticles which endowed the composite with unique simultaneous fluorescence, magnetic and anti-tumor properties. The in-vitro cytotoxicity performed on tumor cells (human osteosarcoma) and normal cells (fibroblasts) showed a selective cytotoxic effect induced after 24 h of treatment by the drug-free composite, leading to a cell death of 37%, for a composite concentration of 0.01 mg/mL per 104 tumor cells, whereas the composite loaded with an antitumor drug (mitoxantrone) boosted the cell death effect to 47% for similar exposure conditions. The method shows high potential as it boosts drug transfer within tumor cells. Different antitumor drugs already in clinical use can be used following their separate or in-cocktail controlled combustion.

The effect of magnetic field exposure on differentiation of magnetite nanoparticle-loaded adipose-derived stem cells.

Magnetic nanoparticles (MNPs) are versatile tools for various applications in biotechnology and nanomedicine. MNPs-mediated cell tracking, targeting and imaging are increasingly studied for regenerative medicine applications in cell therapy and tissue engineering. Mechanical stimulation influences mesenchymal stem cell differentiation. Here we show that MNPs-mediated magneto-mechanical stimulation of human primary adipose derived stem cells (ADSCs) exposed to variable magnetic field (MF) influences their adipogenic and osteogenic differentiation. ADSCs loaded with biocompatible magnetite nanoparticles of 6.6 nm, and with an average load of 21 picograms iron/cell were exposed to variable low intensity (0.5 mT - LMF) and higher intensity magnetic fields (14.7 and 21.6 mT - HMF). Type, duration, intensity and frequency of MF differently affect differentiation. Short time (2 days) intermittent exposure to LMF increases adipogenesis while longer (7 days) intermittent as well as continuous exposure favors osteogenesis. HMF (21.6 mT) short time intermittent exposure favors osteogenesis. Different exposure protocols can be used to increase differentiation dependently on expected results. Magnetic remotely-actuated MNPs up-taken by ADSCs promotes the shift towards osteoblastic lineage. ADSCs-MNPs under MF exposure could be used for enabling osteoblastic conversion during cell therapy for systemic osteoporosis. Current results enable further in vivo studies investigating the role of remotely-controlled magnetically actuated ADSCs-MNPs for the treatment of osteoporosis.

Soft Ferromagnetic Bulk Metallic Glass with Potential Self-Healing Ability.

A new concept of soft ferromagnetic bulk metallic glass (BMG) with self-healing ability is proposed. The specific [Fe36Co36B19.2Si4.8Nb4]100-x(Ga)x (x = 0, 0.5, 1 and1.5) BMGs prepared by copper mold casting were investigated as a function of Ga content. The Ga-containing BMGs still hold soft magnetic properties and exhibit large plastic strain of 1.53% in compression. Local melting during shearing produces molten droplets of several µm size throughout the fracture surface. This concept of local melting during shearing can be utilized to produce BMGs with self-healing ability. The molten regions play a vital role in deflecting shear transformation zones, thereby enhancing the mechanical properties.