Presence Of Magnetic Nanoparticles Research Articles

Magnetic zinc oxide/silica microbeads for the photocatalytic degradation of azo dyes

Photocatalysis is a promising technique for the complete degradation of azo dyes that are present in wastewater. In this work, a new photocatalyst in the form of ZnO/Fe3O4/SiO2 hybrid microbeads was fabricated for the photocatalytic degradation of methylene blue. The microbeads were synthesised through self-assembly and subsequent agglomeration of nanoparticles within an aqueous phase of a water-in-oil emulsion template. Photocatalytic degradation experiments were conducted through exposure of a methylene blue solution to UV light. The hybrid microbeads performed better than ZnO powder at the same initial dye and ZnO concentration because of higher adsorption and degradation. The initial concentration of dye solution and catalyst dosage have a significant impact on the degradation. Higher degradation is seen with lower initial dye concentration and higher catalyst dosage. The presence of magnetic nanoparticles within the beads allows for their full recovery and reuse for degradation experiments. Complete degradation of dye was achieved using the new ZnO/Fe3O4/SiO2 microbeads.

Heating efficiency of agarose samples doped with magnetic nanoparticles subjected to ultrasonic and magnetic field

Recently, magneto-ultrasound heating of tissue in the presence of magnetic nanoparticles (NPs) has been studied due to its high potential for use in oncological hyperthermia. It has been published that a synergistic effect, generation of additional heat caused by magneto-ultrasonic coupling, was observed in a tissue-mimicking material (TMM) enriched with magnetic NPs. The specific absorption rate (SAR) was determined from the temperature rise measurements in a focus of the ultrasound beam. It is important to use precise measurement methods when considering medical applications, for which there are limitations to the power of each field, resulting from the prevention of biological phenomena dangerous to the patient. This study demonstrates that in magneto-ultrasonic heating SAR can be measured much more accurately if the ultrasonic field is almost uniform. Measurements were performed on TMM containing Fe3O4 NPs with a diameter of approximately 8 nm and superparamagnetic properties. Both, the measurement and simulation results showed that the errors resulting from the inaccuracy of placing the temperature probe are smaller than in the case of the focused ultrasound. At the same time, the temperature increase caused by the ultrasonic field is almost linear and the influence of heat convection on the SAR determination is negligible. The measurements showed that magneto-ultrasonic hyperthermia can provide the desired thermal effect at lower ultrasound powers and magnetic fields compared to ultrasonic or magnetic hyperthermia used alone. No synergy effect was recorded.

Magnetic Multienzyme@Metal-Organic Material for Sustainable Biodegradation of Insoluble Biomass.

Biodegradation of insoluble biomass such as cellulose via carbohydrase enzymes is an effective approach to break down plant cell walls and extract valuable materials therein. Yet, the high cost and poor reusability of enzymes are practical concerns. We recently proved that immobilizing multiple digestive enzymes on metal-organic materials (MOMs) allows enzymes to be reused via gravimetric separation, improving the cost efficiency of cereal biomass degradation [ACS Appl. Mater. Interfaces 2021, 13, 36, 43085-43093]. However, this strategy cannot be adapted for enzymes whose substrates or products are insoluble (e.g., cellulose crystals). Recently, we described an alternative approach based on magnetic metal-organic frameworks (MOFs) using model enzymes/substrates [ACS Appl. Mater. Interfaces 2020, 12, 37, 41794-41801]. Here, we aim to prove the effectiveness of combining these two strategies in cellulose degradation. We immobilized multiple carbohydrase enzymes that cooperate in cellulose degradation via cocrystallization with Ca2+, a carboxylate ligand (BDC) in the absence and presence of magnetic nanoparticles (MNPs). We then compared the separation efficiency and enzyme reusability of the resultant multienzyme@Ca-BDC and multienzyme@MNP-Ca-BDC composites via gravimetric and magnetic separation, respectively, and found that, although both composites were effective in cellulose degradation in the first round, the multienzyme@MNP-Ca-BDC composites displayed significantly enhanced reusability. This work provides the first experimental demonstration of using magnetic solid supports to immobilize multiple carbohydrase enzymes simultaneously and degrade cellulose and promotes green/sustainable chemistry in three ways: (1) reusing the enzymes saves energy/sources to prepare them, (2) the synthetic conditions are "green" without generating unwanted wastes, and (3) using our composites to degrade cellulose is the first step of extracting valuable materials from sustainable biomasses such as plants whose growth does not rely on nonregeneratable resources.

Impact of Choline Hydroxide-Supported Magnetic Nanoparticles on Peroxidase Activity and Conformational Stability of Cytochrome c.

Nanotechnology has advanced significantly; however, little is known about the potential implications on human health-related issues, particularly blood carrying enzymes. Ionic liquids are also well-recognized for maintaining the structure and activity of enzymes. In this regard, we delineate a facile synthetic approach of preparation of Fe3O4 nanoparticles (NPs) as well as choline hydroxide [CH][OH] ionic liquid (IL)-supported Fe3O4 NPs (Fe3O4-CHOH). This approach of combining magnetic nanoparticles (MNPs) with IL results in distinctive properties, which may offer enormous utility in the field of biomedical research due to the effortless separation of MNPs by an external magnetic field. Detailed characterization of MNPs including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) was carried out. The biomolecular interactions of Fe3O4 and Fe3O4-CHOH NPs with cytochrome c (Cyt c) were studied in detail using various spectroscopic and microscopic techniques. From spectroscopic studies, it can be concluded that the secondary structure of Cyt c is more stable in the presence of Fe3O4-CHOH NPs than Fe3O4 NPs. The binding constant of Cyt c in the presence of MNPs was also calculated using the Benesi-Hildebrand equation. Furthermore, dynamic light scattering (DLS), ζ-potential, and microscopic studies were performed to study the interaction of Cyt c with MNPs. These studies provided evidence favoring the formation of bionanoconjugates of Cyt c with MNPs. Moreover, the enzymatic activity of Cyt c increases in the presence of both MNPs. The peroxidase activity of Cyt c in MNPs explicitly elucidates that the enzyme is preserved for a long time in the presence of Fe3O4-CHOH NPs. Later on, TEM and field emission scanning electron microscopy (FESEM) were also performed to gather more information regarding the morphology of Cyt c in the presence of MNPs.

Binder-free ultrathin pellets of nanocomposites based on Fe3O4@nitrogen-doped reduced graphene oxide aerogel for electromagnetic interference shielding

The synergistic effects of a hybrid nanocomposite (Fe3O4@NrGO) and their influence on electromagnetic pollution shielding (EMI SE) were explored. This is a current concern where the impacts need to be fully clarified and assertively addressed. Thus, the main focus of the paper was based on the physical and mechanical properties of porosity, surface area, flexibility and, mainly, electrical conductivity of the graphene aerogels, which do not require the use of a binder and are of great interest for the EMI SE area. The precursors (rGO, NrGO and Fe3O4), as well as the nanocomposite, underwent thorough structural characterisation to understand their nature. Characteristic bands of C-N/C=N bonds and a content of 8.03 at% N were identified, with a high N:O ratio of 1.31, indicating efficient doping of the conductive matrix. The aerogel NrGO phase, with a quality of just 5 layers, and the Fe3O4 phase, with domains around 5 nm, were confirmed, as well as the superposition of the signals in the Fe3O4@NrGO pattern. Electron microscopy images and elemental map also demonstrated the efficient distribution of Fe3O4 in the matrix and its porous appearance. Thus, leveraging the advantages of aerogel, extremely light ultra-thin pellets measuring 0.1 mm and weighing 10 mg were produced. The high nitrogen doping of the graphene network, the presence of magnetic nanoparticles, as well as the high surface area and porosity achieved in the production of the nanocomposite, were responsible for high specific shielding effectiveness of 2730 dB · cm−1 at 10.7 GHz and an average in the X-band of 1590 dB · cm−1. Thus, the improved and synergistic mechanisms highlighted the promising advantages of using these highly porous doped materials, demonstrating that the Fe3O4@NrGO hybrid presents high value for investigations in the application of EMI SE.

Nanocomposites Based on Magnetic Nanoparticles and Metal-Organic Frameworks for Therapy, Diagnosis, and Theragnostics.

In the last two decades, metal-organic frameworks (MOFs) with highly tunable structure and porosity, have emerged as drug nanocarriers in the biomedical field. In particular, nanoscaled MOFs (nanoMOFs) have been widely investigated because of their potential biocompatibility, high drug loadings, and progressive release. To enhance their properties, MOFs have been combined with magnetic nanoparticles (MNPs) to form magnetic nanocomposites (MNP@MOF) with additional functionalities. Due to the magnetic properties of the MNPs, their presence in the nanosystems enables potential combinatorial magnetic targeted therapy and diagnosis. In this Review, we analyze the four main synthetic strategies currently employed for the fabrication of MNP@MOF nanocomposites, namely, mixing, in situ formation of MNPs in presynthesized MOF, in situ formation of MOFs in the presence of MNPs, and layer-by-layer methods. Additionally, we discuss the current progress in bioapplications, focusing on drug delivery systems (DDSs), magnetic resonance imaging (MRI), magnetic hyperthermia (MHT), and theragnostic systems. Overall, we provide a comprehensive overview of the recent advances in the development and bioapplications of MNP@MOF nanocomposites, highlighting their potential for future biomedical applications with a critical analysis of the challenges and limitations of these nanocomposites in terms of their synthesis, characterization, biocompatibility, and applicability.

Fe3O4@Zeolite‐Y Functionalized with N‐Methylimidazolium Ionic Liquid: Design and Performance as a New Recyclable and Magnetically Nanocatalyst in the Three‐Component Synthesis of N‐Heterocyclic‐1,3‐thiazolidinones

AbstractIn this research, first, nanoporous zeolite‐NaY was functionalized with 3‐chloropropyltriethoxysilane (organic linker) and then N‐methylimidazole group. Then magnetic nanoparticles (Fe3O4) under ultrasonic energy conditions on the surface and internal pores of zeolite‐Y (1‐MeIm IL@ZY‐Fe3O4) were formed. The identification, confirmation of the structure and morphology of the prepared magnetic nanohybrid was done by using FTIR, FESEM, TEM, EDX, TGA, XRD, VSM and BET instrumental techniques. Next, its catalytic performance in the synthesis of a number of 3‐benzimidazolyl (or benzothiazolyl)‐1,3‐thiazolidin‐4‐one derivatives was investigated through the three‐component condensation reaction of various aromatic aldehydes, 2‐aminobenzimidazole or 2‐aminobenzothiazole, and thioglycolic acid in EtOH at room temperature. The results of the experiments show that the presence of magnetic nanoparticles (Fe3O4) inside the pores of zeolite functionalized with ionic liquid not only causes easy and quick separation of the nanocatalyst by an external magnetic field but also can be effective in catalyzing the reaction as a Lewis acid.

Frictional contribution in nanomagnetic particles substituted magnetorheological fluid

A series of Fe flake-based MR fluids were prepared using a ferrofluid as a dispersion medium. The concentration of micron-size particles was kept constant, and the nanoparticle concentration was varied. The MR fluids were characterised structurally and rheologically. The experimental results were fitted with various models.This paper aims to elucidate how the frictional behaviour of the flakes is modified in the presence of magnetic nanoparticles. The measurements were carried out on fluid flow under different conditions, such as applied magnetic field, shear rate, and stress. The data was analysed using the recent PUP (Pisuwala-Upadhyay-Parekh) rheology model. The results clearly show that the friction between the anisotropic particles decreases with an increase in nanoparticle concentration. The conclusion is further enforced by testing a commercial MRF with spherical particles.

Nano Freezing-Thawing of Atlantic Salmon Fillets: Impact on Thermodynamic and Quality Characteristics.

The presence of magnetic nanoparticles (MNPs) suppresses ice nucleation and growth during freezing and thawing. In this study, the effects of MNPs-assisted cryogenic freezing integrated with MNP-combined microwave thawing (NNMT) on the thermodynamic and quality changes of salmon fillets were investigated. Results have shown that NNMT raises Tg (glass transition temperature) and Tmax (transition temperature), thus improving the storage stability of salmon fillets. MNPs-assisted freezing and thawing treatment, especially NNMT treatment, significantly improved the water holding capacity, texture, color, and other quality characteristics of salmon fillets. In addition, the lipid and protein oxidation degrees of the NNMT treatment were the lowest, while the myofibrillar protein solubility of NNMT was the highest (87.28%). This study demonstrated that NNMT has minimal impact on the freezing-thawing quality of salmon fillets, making it a more suitable option for the preservation of aquatic foods.

Rational design of stimuli‐responsive magnetic polymer hybrid (nano)materials

AbstractCombining organic and inorganic materials is a fascinating strategy to produce hybrid materials that combine the advantages of both polymeric and inorganic materials. Among the various types of organic–inorganic hybrids, stimuli‐responsive magnetic polymer hybrids (RMPHs) are particularly promising materials for a wide variety of applications. While the magnetic properties are generally provided by the presence of magnetic nanoparticles, such as iron oxide nanoparticles, the polymeric compound brings the stimuli‐responsiveness, e.g. responsiveness to pH, temperature, redox reaction or irradiation. Furthermore, as the chemical structure and architecture of the polymeric materials are diverse and easily tunable, stimuli‐RMPHs have found applications in various domains, including catalysis, biotechnology, (bio)imaging and cancer therapy. Given the importance of the hybrids' shape and morphology for the targeted application, this review presents the possible synthetic strategies to rationally design stimuli‐RMPHs of various morphologies ranging from nanometric core–shell structures to nanogels, microgels and membranes. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Opposite effects produced by magnetic nanoparticles:Phospholipid films generated at a liquid/liquid interface, in the drug transfer processes

The interaction between Fe3O4 magnetic nanoparticles (MNPs) coated with polysaccharides, and different phospholipids adsorbed at a water|1,2-dichloroethane interface, was studied employing cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and capacity curves. For this study, an anionic phospholipid, distearoyl phosphatidic acid (DSPA), and a zwitterionic phospholipid distearoyl phosphatidylethanolamine (DSPE) were used, which have the same carbonated chain. Fe3O4 nanoparticles were coated with two different polysaccharides, one lineal, chitosan (CHI), and other with a branched structure, diethylaminoethyl dextran (DEAE-D), both commonly used in medical applications. The effect of the MNPs coating agents in the final interaction with MNPs:phospholipid hybrid films was evaluated. EIS confirm that the presence of Fe3O4@CHI:DSPA mixture film conduces to a homogeneous film at the interface, in contrast, for Fe3O4@DEAE-D:DSPA mixture films, conduces to a inhomogeneous film with pores formation. In addition, the effect of this hybrid films (MNPs:phospholipid) in the anionic diclofenac (DCFNC−) and cationic triflupromazine (HTFPZ+) transfer process across the water|1,2-dichloroethane interface was studied. It was demonstrated that Fe3O4@CHI:DSPA film can totally block DCFNC− transfer process but for Fe3O4@DEAE-D:DSPA or DSPE film the DCFNC− can transfer across the uncovered zones present at the interface. Otherwise, for positively charged HTFPZ+, the drug transfer is higher in presence of MNPs:phospholipid mixture film due to a sum of effects, electrostatic interaction between HTFPZ+ and phospholipid and hydrophobic interactions between HTFPZ+ and polysaccharide coated MNPs.

Coupling of cationic porphyrins on manganese ferrite nanoparticles: A potential multifunctional nanostructure for theranostics applications

We present here the coupling of cationic meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (TMPyP) and their zinc complex (ZnTMPyP) with magnetic nanoparticles (MNPs) of manganese ferrite (MnFe2O4) covered with citric acid (CA), dimercaptosuccinic acid (DMSA), and tripolyphosphate (TPP). In the presence of MNPs, the fluorescence emission of porphyrins was suppressed through static fluorescence quenching. Stern-Volmer method was employed to determine the binding constants (Kb) between porphyrins and MNPs. These interactions were described based on the coating layer properties and the unfunctionalized metallic sites on the surface of MNPs. The higher binding constants (Kb) were observed for TPP and CA MNPs (KbTPP < KbCA), which possess a poor recovery coefficient. In this case, the residuals unfunctionalized Fe3+/Mn2+ atomic sites on the MNPs surface can interact with nitrogen atoms of macrocyclic ring of free base porphyrin and the free oxygens from carboxylate and phosphate groups interact with amino hydrogens of porphyrin ring through hydrogen bonds. For ZnTMPyP, can occur a coordination of zinc atoms by the carboxylate or phosphate groups that are able to form strong and stable interactions. Furthermore, it was observed that while porphyrins are bound to MNPs, fluorescence emission and singlet oxygen production are reduced. However, such properties were recovered after the release of porphyrins from MNPs. To investigate the molecules release, a proof-of-concept photothermal experiment was designed and performed, where temperatures higher than 50 °C were reached. These results show that this system combines properties which can be employed for development of drug delivery system, magnetic tracers for alternating current biosusceptometry (ACB), as well as application of photodynamic (PDT), photothermal therapy (PTT) and magnetic hyperthermia (MHT) therapies.

Cr-Zn/Ni-Containing Nanocomposites as Effective Magnetically Recoverable Catalysts for CO2 Hydrogenation to Methanol: The Role of Metal Doping and Polymer Co-Support

CO2 hydrogenation to methanol is an important process that could solve the problem of emitted CO2 that contributes to environmental concern. Here we developed Cr-, Cr-Zn-, and Cr-Ni-containing nanocomposites based on a solid support (SiO2 or Al2O3) with embedded magnetic nanoparticles (NPs) and covered by a cross-linked pyridylphenylene polymer layer. The decomposition of Cr, Zn, and Ni precursors in the presence of supports containing magnetic oxide led to formation of amorphous metal oxides evenly distributed over the support-polymer space, together with the partial diffusion of metal species into magnetic NPs. We demonstrated the catalytic activity of Cr2O3 in the hydrogenation reaction of CO2 to methanol, which was further increased by 50% and 204% by incorporation of Ni and Zn species, respectively. The fine intermixing of metal species ensures an enhanced methanol productivity. Careful adjustment of constituent elements, e.g., catalytic metal, type of support, presence of magnetic NPs, and deposition of hydrophobic polymer layer contributes to the synergetic promotional effect required for activation of CO2 molecules as well. The results of catalytic recycle experiments revealed excellent stability of the catalysts due to protective role of hydrophobic polymer.

Synthetic and natural ester-based nanofluids with fullerene and magnetite nanoparticles – An experimental AC breakdown voltage study

Ester-based electrical insulating liquids constitute an attractive alternative to widely used mineral oils, especially due to their ecological benefits. In this study, we present an experimental comparison of AC breakdown voltage (BDV) in both natural and synthetic ester-based nanofluids with various concentrations of fullerene (C60) and magnetite (Fe3O4) nanoparticles. The BDV measurement was conducted with an AC voltage rise rate of 2 kV/s according IEC 60156 standard. While the suspensions of magnetite nanoparticles exhibited increased AC BDV for all samples tested, the fullerene-based nanofluids exhibited the enhanced AC BDV only for two among six nanoparticle concentrations. Accordingly, we present a comparative view of the electrical breakdown development using statistical descriptors. This study uses Weibull and normal distributions for statistical analysis to estimate AC breakdown voltage at different cumulative probability levels 1 %, 10 %, and 50 %. The parameters of theoretical distributions are fitted to the experimental data. Subsequently, statistical test of conformity to the distributions, and their skewness and kurtosis are analysed. The analysis reveals that AC BDV of nanofluids increases with the increasing cumulative probability more than those of pure esters. It is shown that the addition of fullerene nanoparticles tends to reduce AC BDV in the natural ester but not in the synthetic ester. The presence of magnetic nanoparticles in both esters yielded an enhancement of the AC BDV but in a different measure.

Synthesis of a reusable magnetic photocatalyst based on carbon xerogel/TiO2 composites and its application on acetaminophen degradation

This work describes the production photocatalyst in two steps, (1) production of N-CXTi nanocomposites by sol-gel polymerization of resorcinol-formaldehyde-melamine in the presence of K2TiF6 inorganic metallic salt with TiO2 as precursor; (2) Synthesis of the Fe3O4/N-CXTi and Fe3O4/SiO2/N-CXTi nanocomposites by mechanical mixing of N-CXTi and magnetic nanoparticles. The magnetic nanoparticles (Fe3O4 and Fe3O4/SiO2) were prepared by a chemical co-precipitation method and subsequent functionalization by silica (SiO2). The materials were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry, and textural properties. The composites presented a morphology heterogeneous structure and the presence of two phases for the introduction of TiO2. The region was formed by amorphous carbon and carbon spheres, where Ti is detected only immersed in the amorphous carbon particles, in the anatase and rutile phase, and the presence of magnetic nanoparticles is located surrounded by the carbon structure. Results for the recovery and reuse of the photocatalyst Fe3O4/SiO2/N-CXTi presented the highest efficiency in the removal of the acetaminophen (APP) in the aqueous medium; the result of the reaction carried out in the presence of ultraviolet irradiation showed that the magnetic photocatalyst removed 99.2% of APP in an aqueous medium. Results for the recovery and reuse of the photocatalysts for nine consecutive reactions showed that they can be separated from the reaction medium in a simple and fast way, without significant losses of photocatalytic efficiency and excellent recovery of the photocatalyst.

Magnetic nanoparticles embedded in microlasers for controlled transport in different sensing media

In recent years, whispering gallery mode microlasers have attracted tremendous interest in sensing due to their ultra-high sensitivity at atomic levels. However, due to the non-magnetic properties, it is difficult to locate the microlasers at hard-to-reach positions, thus, limiting their sensing potential in many in-vitro and in-vivo applications. In this work, we report magnetic microlasers fabricated by encapsulating Ni0.2Zn0.8Fe2O4 magnetic nanoparticles (MNPs) within their cavity made of bovine serum albumin. The presence of MNPs allows the transportable actuation of the magnetic microlasers while maintaining lasing emission characteristics. Microlasers with various concentrations of MNPs are investigated to identify the optimum concentration that can balance a good magnetization, a low lasing threshold, and a high quality (Q) factor. These magnetic microlasers can be employed for sensing applications where sensors need to be navigated through different sensing media. As a proof of concept, we observed a clear shift of lasing wavelength of a magnetic microlaser while dragging it through different adjacent media by magnetic navigation. This result demonstrates the potential applications of magnetic microlasers for future biological and chemical applications.

Multiple slip, Soret and Dufour effects in fluid flow near a vertical stretching sheet in the presence of magnetic nanoparticles

This paper presents a mathematical analysis of multiple slip, Soret and Dufour effects in a boundary layer flow of an electrically conducting nanofluid over a vertically stretching sheet. The flow situation has been described mathematically by using partial differential equations. Suitable transformations are utilized to make the model equation convenient for computation. An efficient optimal homotopy analysis method has been implemented successfully to obtain analytic approximations to the unknown functions in the flow problem. The influences of wall slip parameters, porosity of the medium, Buoyancy forces, magnetic field, thermal radiation, Soret and Dufour effects, heat source and chemical reaction parameters are examined in detail. The variations of the dimensionless velocity, temperature and concentration profiles in relation to the emerging parameters are explored intensively. The rates of momentum, heat and mass transfer near the stretching surface are also studied against the pertinent parameters. The study reveals that the increase in velocity slip parameter speeds up the fluid motion and increasing the Soret effect raises concentration of nanoparticles near the stretching sheet. Further, the analytic approximations for the solutions of the present model obtained by implementing the optimal homotopy analysis method are found in a very good agreement with some early works under common assumptions.

Effects of radiofrequency exposure on in vitro blood-brain barrier permeability in the presence of magnetic nanoparticles

The blood-brain barrier (BBB) remains a major obstacle for the delivery of drugs in the treatment of many neurological diseases. In this study, we aimed to investigate the effects of radiofrequency electromagnetic fields (RF-EMFs) on the permeability of an in vitro BBB model under RF exposure alone, or in the presence of nanoparticles (NPs). For this purpose, an in vitro BBB model was established by seeding human umbilical vein endothelial cells (HUVECs) and human glioblastoma cell line (T98G) on the apical and basolateral sides of the transwell membrane, respectively. The integrity of the BBB model was confirmed by measuring transendothelial electrical resistance (TEER), and a fluorescein isothiocyanate (FITC)-dextran permeability assay was performed when the resistance reached 120 Ω cm2. After the RF-field exposure (13.56 MHz, 80 W, 10 min), we found that FITC-dextran transported across the in vitro BBB was increased 10-fold compared to FITC-dextran transported without an RF-field. This notable phenomenon, which can be called the burst permeability RF effect (BP-RF), has been proposed for the first time in the literature. Subsequently, the effect of the RF-field on BBB permeability was also investigated in the presence of superparamagnetic iron oxide nanoparticles (SPIONs) and magnetic poly(lactic-co-glycolic acid)-polyethylene glycol (PLGA-b-PEG) nanoparticles (m-PNPs). It was found that the amount of both transported NPs on the basolateral sides increased after exposure to the RF-field. As a result, the RF-field can be applied simultaneously during treatment with clinical agents or nanocarriers, improving the permeability of the BBB, which may contribute to therapeutic efficacy of many drugs that are used in neurological diseases.

Nano-Fe3O4/In: a heterogeneous magnetic nanocatalyst for synthesis of tetrazole derivatives under solvent-free conditions

We prepared magnetically recoverable Fe3O4/In nanoparticles as a heterogeneous, economically, and nontoxic catalyst for producing 5-substituted-tetrazoles. A suitable, quick, and highly efficient method for synthesis of 5-substituted-1H-tetrazoles was proposed via a multicomponent reaction of aromatic aldehydes, malononitrile, and sodium azide in the presence of magnetic nanoparticles Fe3O4/In, under solvent-free conditions. Various characterization including XRD, FTIR, SEM, and EDX were performed to recognize the inherent features of the nanoparticles. Design expert software was used to optimize the reaction conditions including reaction temperature, catalyst content, and reaction time. The results show high efficiency, obtained by using a small amount of nanocatalyst. The advantages of this protocol including easy recovery of the nanocatalyst by an external magnet, ability to reuse for five runs without noticeable loss in activity, simple workup, solvent-free, and mild reaction conditions making it interesting from a financial and environmental point of view.

Magnetically Recoverable Nanoparticulate Catalysts for Cross-Coupling Reactions: The Dendritic Support Influences the Catalytic Performance.

Carbon-carbon cross-coupling reactions are among the most important synthetic tools for the preparation of pharmaceuticals and bioactive compounds. However, these reactions are normally carried out using copper, phosphines, and/or amines, which are poisonous for pharmaceuticals. The use of nanocomposite catalysts holds promise for facilitating these reactions and making them more environmentally friendly. In the present work, the PEGylated (PEG stands for poly(ethylene glycol) pyridylphenylene dendrons immobilized on silica loaded with magnetic nanoparticles have been successfully employed for the stabilization of Pd2+ complexes and Pd nanoparticles. The catalyst developed showed excellent catalytic activity in copper-free Sonogashira and Heck cross-coupling reactions. The reactions proceeded smoothly in green solvents at low palladium loading, resulting in high yields of cross-coupling products (from 80% to 97%) within short reaction times. The presence of magnetic nanoparticles allows easy magnetic separation for repeated use without a noticeable decrease of catalytic activity due to the strong stabilization of Pd species by rigid and bulky dendritic ligands. The PEG dendron periphery makes the catalyst hydrophilic and better suited for green solvents. The minor drop in activity upon the catalyst reuse is explained by the formation of Pd nanoparticles from the Pd2+ species during the catalytic reaction. The magnetic separation and reuse of the nanocomposite catalyst reduces the cost of target products as well as energy and material consumption and diminishes residual contamination by the catalyst. These factors as well as the absence of copper in the catalyst makeup pave the way for future applications of such catalysts in cross-coupling reactions.