Magnetic chitosan supported copper particles as a heterogeneous catalyst for benzaldehyde glycol acetal reaction

In this work, a series of magnetic chitosan (CS) supported-metal catalysts were successfully prepared for the acetalization of benzaldehyde (BzH) with ethylene glycol (EG). The structural properties of the catalysts were characterized by TEM, FT-IR, XRD, XPS, TGA-DTG, SEM-EDX and VSM. The results showed that Fe3O4-CS-Cu(20 %) catalyst possessed the best catalytic efficiency in all prepared catalysts due to its suitable acidity and excellent stability when they were utilized in the acetalization reaction to generate benzaldehyde glycol acetal. The response surface methodology based on Box-Behnken design was applied to optimize acetalization reaction conditions with the optimal yield of 96.26 % obtained via 3D surface diagram. The attractive feature of prepared catalysts was easy separation from solutions via an external magnetic field application. This work sheds light on the design of novel chitosan-supported metal catalysts which could be widely applied in acetalization industry.

Role of metal oxide ferrites in the process of magnetic hyperthermia - A review

Extensive research has been conducted on the manufacturing of nano ferrites, and their use in magnetic hyperthermia therapy has shown promising results in cancer treatment. This study aims primarily to provide an overview of the latest developments in the synthesis of magnetic nanoparticles (MNPs) for the treatment of hyperthermia. Magnetic nanoparticles are biocompatible and have a stable magnetic state, nano ferrites have become recognized as apex thermoseeds in biomedical applications, specifically for the treatment of magnetic hyperthermia. Employing dopant materials, biocompatible overlay, and preparation techniques, one may study the effectiveness of nano ferrites. Furthermore, specific requirements need to be met for using nano ferrites in cancer treatments like magnetic hyperthermia. These include low toxicity, biocompatibility, a higher specific absorption rate, a shorter time to reach the targeted hyperthermia temperature, crystalline size within the biological radius, and a lower dose of the nano ferrite. A potential resolution involves identifying the limitations and proposing enhanced nanocomposite materials that amplify their magnetic characteristics via a biocompatible overlay, all while optimizing the effectiveness and functioning of magnetic nanoferrites. To increase the effectiveness of ferrite nanoparticles in treating hyperthermia, this study will figure out their constraints and offer solutions for more effective ferrite-based nanocomposites that may prove to be a viable therapy option for cancer in the future.

Hyperthermia of Magnetically Soft-Soft Core-Shell Ferrite Nanoparticles

Magnetically soft-soft MnFe₂O₄-Fe₃O₄ core-shell nanoparticles were synthesized through a seed-mediated method using the organometallic decomposition of metal acetyl acetonates. Two sets of core-shell nanoparticles (S1 and S2) of similar core sizes of 5.0 nm and different shell thicknesses (4.1 nm for S1 and 5.7 nm for S2) were obtained by changing the number of nucleating sites. Magnetic measurements were conducted on the nanoparticles at low and room temperatures to study the shell thickness and temperature dependence of the magnetic properties. Interestingly, both core-shell nanoparticles showed similar saturation magnetization, revealing the ineffective role of the shell thickness. In addition, the coercivity in both samples displayed similar temperature dependencies and magnitudes. Signatures of spin glass (SG) like behavior were observed from the field-cooled temperature-dependent magnetization measurements. It was suggested to be due to interface spin freezing. We observed a slight and non-monotonic temperature-dependent exchange bias in both samples with slightly higher values for S2. The effective magnetic anisotropy constant was calculated to be slightly larger in S2 than that in S1. The magnetothermal efficiency of the chitosan-coated nanoparticles was determined by measuring the specific absorption rate (SAR) under an alternating magnetic field (AMF) at 200-350 G field strengths and frequencies (495.25-167.30 kHz). The S2 nanoparticles displayed larger SAR values than the S1 nanoparticles at all field parameters. A maximum SAR value of 356.5 W/g was obtained for S2 at 495.25 kHz and 350 G for the 1 mg/mL nanoparticle concentration of ferrogel. We attributed this behavior to the larger interface SG regions in S2, which mediated the interaction between the core and shell and thus provided indirect exchange coupling between the core and shell phases. The SAR values of the core-shell nanoparticles roughly agreed with the predictions of the linear response theory. The concentration of the nanoparticles was found to affect heat conversion to a great extent. The in vitro treatment of the MDA-MB-231 human breast cancer cell line and HT-29 human colorectal cancer cell was conducted at selected frequencies and field strengths to evaluate the efficiency of the nanoparticles in killing cancer cells. The cellular cytotoxicity was estimated using flow cytometry and an MTT assay at 0 and 24 h after treatment with the AMF. The cells subjected to a 45 min treatment of the AMF (384.50 kHz and 350 G) showed a remarkable decrease in cell viability. The enhanced SAR values of the core-shell nanoparticles compared to the seeds with the most enhancement in S2 is an indication of the potential for tailoring nanoparticle structures and hence their magnetic properties for effective heat generation.

Tailoring Interfacial Exchange Anisotropy in Hard-Soft Core-Shell Ferrite Nanoparticles for Magnetic Hyperthermia Applications

Magnetically hard-soft core-shell ferrite nanoparticles are synthesized using an organometallic decomposition method through seed-mediated growth. Two sets of core-shell nanoparticles (S1 and S2) with different shell (Fe3O4) thicknesses and similar core (CoFe2O4) sizes are obtained by varying the initial quantities of seed nanoparticles of size 6.0 ± 1.0 nm. The nanoparticles synthesized have average sizes of 9.5 ± 1.1 (S1) and 12.2 ± 1.7 (S2) nm with corresponding shell thicknesses of 3.5 and 6.1 nm. Magnetic properties are investigated under field-cooled and zero-field-cooled conditions at several temperatures and field cooling values. Magnetic heating efficiency for magnetic hyperthermia applications is investigated by measuring the specific absorption rate (SAR) in alternating magnetic fields at several field strengths and frequencies. The exchange bias is found to have a nonmonotonic and oscillatory relationship with temperature at all fields. SAR values of both core-shell samples are found to be considerably larger than that of the single-phase bare core particles. The effective anisotropy and SAR values are found to be larger in S2 than those in S1. However, the saturation magnetization displays the opposite behavior. These results are attributed to the occurrence of spin-glass regions at the core-shell interface of different amounts in the two samples. The novel outcome is that the interfacial exchange anisotropy of core-shell nanoparticles can be tailored to produce large effective magnetic anisotropy and thus large SAR values.

Specific Absorption Rate Dependency on the Co2+ Distribution and Magnetic Properties in CoxMn1-xFe2O4 Nanoparticles

Mixed ferrite nanoparticles with compositions CoxMn1-xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized by a simple chemical co-precipitation method. The structure and morphology of the nanoparticles were obtained by X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, and Mössbauer spectroscopy. The average crystallite sizes decreased with increasing x, starting with 34.9 ± 0.6 nm for MnFe2O4 (x = 0) and ending with 15.0 ± 0.3 nm for CoFe2O4 (x = 1.0). TEM images show an edge morphology with the majority of the particles having cubic geometry and wide size distributions. The mixed ferrite and CoFe2O4 nanoparticles have an inverse spinel structure indicated by the splitting of A1g peak at around 620 cm-1 in Raman spectra. The intensity ratios of the A1g(1) and A1g(2) peaks indicate significant redistribution of Co2+ and Fe3+ cations among tetrahedral and octahedral sites in the mixed ferrite nanoparticles. Magnetic hysterics loops show that all the particles possess significant remnant magnetization and coercivity at room temperature. The mass-normalized saturation magnetization is highest for the composition with x = 0.8 (67.63 emu/g), while CoFe2O4 has a value of 65.19 emu/g. The nanoparticles were PEG (poly ethylene glycol) coated and examined for the magneto thermic heating ability using alternating magnetic field. Heating profiles with frequencies of 333.45, 349.20, 390.15, 491.10, 634.45, and 765.95 kHz and 200, 250, 300, and 350 G field amplitudes were obtained. The composition with x = 0.2 (Co0.2Mn0.8Fe2O4) with saturation magnetization 57.41 emu/g shows the highest specific absorption rate (SAR) value of 190.61 W/g for 10 mg/mL water dispersions at a frequency of 765.95 kHz and 350 G field strength. The SAR values for the mixed ferrite and CoFe2O4 nanoparticles increase with increasing concentration of particle dispersions, whereas for MnFe2O4, nanoparticles decrease with increasing the concentration of particle dispersions. SARs obtained for Co0.2Mn0.8Fe2O4 and CoFe2O4 nanoparticles fixed in agar ferrogel dispersions at frequency of 765.95 kHz and 350 G field strength are 140.35 and 67.60 W/g, respectively. This study shows the importance of optimizing the occupancy of Co2+ among tetrahedral and octahedral sites of the spinel system, concentration of the magnetic nanoparticle dispersions, and viscosity of the surrounding medium on the magnetic properties and heating efficiencies.

Mesoporous ferromagnetic manganese ferrite nanoparticles for enhanced visible light mineralization of azoic dye into nontoxic by-products

In this study, a one pot facile synthesis of ferromagnetic manganese ferrite nanoparticles (MnFe₂O₄) was carried out using chemical co-precipitation method for mineralization of azo dye (Congo red (CR)) in aqueous solution under visible light irradiation. The synthesized MnFe₂O₄ nanoparticles were highly crystalline and showed face-centred cubic (FCC) structure with average particle size of 58 ± 4 nm. The BET analysis of the MnFe₂O₄ nanoparticles revealed the mesoporous distribution of material with high surface area can provide large electro active sites and short diffusion paths for the transport of ions which plays a vital role in the photocatalytic degradation of CR. The point of zero charge (pH_PZC) was observed to be 6.7 indicating favourable condition for material-anionic dye interaction. The XPS studies revealed that the large amounts of oxygen vacancies were produced due to the defects in the lattice oxygen. The MnFe₂O₄ nanoparticles mineralised 98.3 ± 0.2% of 50 mg/L CR within 30 min when tested in photocatalytic reactor under 565 nm. The particles were recoverable under the influence of an external magnet after the photocatalytic reaction and were reusable. The recovered nanoparticles showed 96% of CR degradation efficiency even after five cycles of reuse. The by-product analysis with GC-MS indicated mineralization of CR into simple alcohols and acids. The aqueous solution containing mineralised CR was nontoxic to Trigonella foenumgraecum and Vigna mungo seeds and favoured increased germination, plumule and radicle length when compared to untreated CR.

Molecular Stereocomplexation for Enhancing the Stability of Nanoparticles Encapsulated in Polymeric Micelles for Magnetic Resonance Imaging

A generalizable approach for improving the stability of polylactide-based (PLA-based) micelles for encapsulating nanoparticles (NPs) is demonstrated, using stereocomplexation between a pair of poly (ethylene glycol)-b-poly(d-lactide)/poly(ethylene glycol)-b-poly(l-lactide) block copolymer blends. Three different superparamagnetic ferrite-based NPs with distinct nanostructures are first prepared by the high-temperature pyrolysis method, including spherical MnFe₂O₄, cubic MnFe₂O₄, and core-shell MnFe₂O₄@Fe₃O₄. The diameters of these NPs are approximately 7-10 nm as revealed by transmission electron microscopy. These hydrophobic NPs can be encapsulated within self-assembled, stereocomplexed PLA (sc-PLA) micelles. All sc-PLA micelle systems loaded with three different NPs exhibit enhanced stability at elevated temperatures (20-60 °C) and with extended storage time (∼96 h) compared with analogous samples without stereocomplex formation, confirmed by dynamic light scattering measurements. The magnetic NP-loaded micelles with mean diameters of approximately 150 nm show both biocompatibility and superparamagnetic property. Under a 1.5 T magnetic field, cubic MnFe₂O₄ (c-MnFe₂O₄)-loaded micelles exhibit an excellent negative contrast enhancement of MR signals (373 mM^-1·s^-1), while core-shell MnFe₂O₄@Fe₃O₄-loaded micelles show a slightly lower signal for MR imaging (275 mM^-1·s^-1). These results suggest the potential of using sc-PLA-based polymer micelles as universal carriers for magnetic resonance imaging contrast agents with improved stability for different applications such as cancer diagnosis.

Relaxivity of manganese ferrite nanoparticles

Manganese ferrite nanoparticles are superparamagnetic and have very high saturation magnetization, which makes them candidates for application as MRI contrast agents. Because these nanoparticles are very effective enhancers of transverse relaxation, they are particularly suitable as negative (T₂-weighted) contrast agents. The magnitude of the relaxivity of nanoparticulate Mn ferrites seems to be determined mainly by the method of preparation, their dimensions, and their saturation magnetization.

Influence of Oxidation Degree of Graphene Oxide on Its Nuclear Relaxivity and Contrast in MRI

Graphene oxide (GO) serves as a versatile platform for various applications, with the oxygen content of GO playing an important role in governing its properties. In the present study, different GO types covering a wide range of oxidation degree were prepared using our newly developed two-step method involving ball milling of graphite followed by its oxidation to GO. In addition to the variations in their physicochemical properties, the different GO types exhibited differences in proton relaxivity due to their paramagnetic nature. Nuclear magnetic resonance spectroscopy studies showed that the degree of oxidation of GO perturbs its nuclear relaxation properties and, together with intercalated Mn2+ ions, provides large contrast variation in magnetic resonance imaging (MRI). The study for the first time reveals that the surface chemistry of GO affects its relaxivity and opens up new avenues for developing tunable GO-based contrast agents in magnetic resonance imaging for diagnostics and therapies.

Magnetic Nanoparticles as In Vivo Tracers for Alzheimer’s Disease

Drug formulations and suitable methods for their detection play a very crucial role in the development of therapeutics towards degenerative neurological diseases. For diseases such as Alzheimer’s disease, magnetic resonance imaging (MRI) is a non-invasive clinical technique suitable for early diagnosis. In this review, we will discuss the different experimental conditions which can push MRI as the technique of choice and the gold standard for early diagnosis of Alzheimer’s disease. Here, we describe and compare various techniques for administration of nanoparticles targeted to the brain and suitable formulations of nanoparticles for use as magnetically active therapeutic probes in drug delivery targeting the brain. We explore different physiological pathways involved in the transport of such nanoparticles for successful entry in the brain. In our lab, we have used different formulations of iron oxide nanoparticles (IONPs) and protein nanocages as contrast agents in anatomical MRI of an Alzheimer’s disease (AD) brain. We compare these coatings and their benefits to provide the best contrast in addition to biocompatibility properties to be used as sustainable drug-release systems. In the later sections, the contrast enhancement techniques in MRI studies are discussed. Examples of contrast-enhanced imaging using advanced pulse sequences are discussed with the main focus on important studies in the field of neurological diseases. In addition, T1 contrast agents such as gadolinium chelates are compared with the T2 contrast agents mainly made of superparamagnetic inorganic metal nanoparticles.

Preparation of chitosan based magnetic nanocomposite for tetracycline adsorption: Kinetic and thermodynamic studies

In the present study, the magnetic nanocomposite is fabricated using chitosan, thiobarbituric acid, malondialdehyde and Fe₃O₄ nanoparticles (CTM@Fe₃O₄). The fabricated nanocomposite (CTM@Fe₃O₄) is characterized using FTIR, TGA, BET, XRD, Raman, XPS, FESEM, and HRTEM techniques. The results of BET analysis confirmed that the nanocomposite has a mesoporous structure with high surface area of 376 m² g^-1 and high pore volume 0.3828 cm³ g^-1. The adsorption of tetracycline (TC) onto CTM@Fe₃O₄ adsorbent is carried out using batch technique by changing several factors such as pH, concentration, contact time, and temperature. Langmuir and pseudo-second-order nonlinear models were found to be the best-fit models to predict isotherms and kinetics of adsorption, respectively. The highest adsorption capacity of 215.31mg/g was achieved at the optimum conditions of 0.05g adsorbent dosage, 60mg/L TC concentration. Overall, results demonstrated that CTM@Fe₃O₄ nanocomposite was an excellent adsorbent material with superparamagnetic properties, which allowed the separation as well as recovery of the adsorbent from aqueous solution using external magnet for effective industrial applications.

Principles of Magnetic Hyperthermia: A Focus on Using Multifunctional Hybrid Magnetic Nanoparticles

Hyperthermia is a noninvasive method that uses heat for cancer therapy where high temperatures have a damaging effect on tumor cells. However, large amounts of heat need to be delivered, which could have negative effects on healthy tissues. Thus, to minimize the negative side effects on healthy cells, a large amount of heat must be delivered only to the tumor cells. Magnetic hyperthermia (MH) uses magnetic nanoparticles particles (MNPs) that are exposed to alternating magnetic field (AMF) to generate heat in local regions (tissues or cells). This cancer therapy method has several advantages, such as (a) it is noninvasive, thus requiring surgery, and (b) it is local, and thus does not damage health cells. However, there are several issues that need to achieved: (a) the MNPs should be biocompatible, biodegradable, with good colloidal stability (b) the MNPs should be successfully delivered to the tumor cells, (c) the MNPs should be used with small amounts and thus MNPs with large heat generation capabilities are required, (d) the AMF used to heat the MNPs should meet safety conditions with limited frequency and amplitude ranges, (e) the changes of temperature should be traced at the cellular level with accurate and noninvasive techniques, (f) factors affecting heat transport from the MNPs to the cells must be understood, and (g) the effect of temperature on the biological mechanisms of cells should be clearly understood. Thus, in this multidisciplinary field, research is needed to investigate these issues. In this report, we shed some light on the principles of heat generation by MNPs in AMF, the limitations and challenges of MH, and the applications of MH using multifunctional hybrid MNPs.

Controllable synthesis of a novel magnetic core-shell nanoparticle for dual-modal imaging and pH-responsive drug delivery

In this study, novel magnetic core-shell nanoparticles Fe₃O₄@La-BTC/GO have been synthesized by the layer-by-layer self-assembly (LBL) method and further modified by attachment of amino-modified PEG chains. The nanoparticles were thoroughly characterized by x-ray diffraction, FTIR, scanning electron microscopy and transmission electron microscopy. The core-shell structure was shown to be controlled by the LBL method. The drug loading of doxorubicin (DOX) within the Fe₃O₄@La-BTC/GO-PEG nanoparticles with different numbers of deposited layers was investigated. It was found that DOX loading increased with increasing number of metal organic framework coating layers, indicating that the drug loading can be controlled through the controllable LBL method. Cytotoxicity assays indicated that the Fe₃O₄@La-BTC/GO-PEG nanoparticles were biocompatible. The DOX was released rapidly at pH 3.8 and pH 5.8, but at pH 7.4 the rate and extent of release was greatly attenuated. The nanoparticles therefore demonstrate an excellent pH-triggered drug release. In addition, the particles could be tracked by magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI). A clear dose-dependent contrast enhancement in T ₂-weighted MR images and fluorescence images indicate the potential of these nanoparticles as dual-mode MRI/FOI contrast agents.

Effect of core–shell nanoparticle geometry on the enhancement of the proton relaxivity value in a nuclear magnetic resonance experiment

This work illustrates the effect of core–shell nanoparticle geometry on the enhancement of the proton relaxivity value in a nuclear magnetic resonance experiment.

Controlling the magnetic properties of polymer–iron oxide nanoparticle composite thin films via spatial particle orientation

We investigated the effect of Fe₃O₄ nanoparticle orientation on the magnetic properties of hybrid polymer nanocomposite thin films.