Magnetically responsive chitosan-pectin films incorporating Fe3O4 nanoparticles with enhanced antimicrobial activity.

Chitosan-pectin films with iron oxide (Fe3O4) magnetic nanoparticles were prepared by solution casting in order to produce biopolymer based magnetically active materials. Infrared (FTIR) spectra indicated physical interactions between the matrix and nanoparticles, corroborated by differential scanning calorimetry (DSC) results. In addition, thermal characterization suggested that the interactions between chitosan, pectin and the nanoparticles resulted in a less compact structure, influencing the film mechanical properties. Regarding vibrating-sample magnetometry (VSM) and electrical analysis, chitosan-pectin films with Fe3O4 nanoparticles showed ferrimagnetic behavior, with an increase of the dielectric constant as the nanoparticle concentration increased. Furthermore, films displayed enhanced antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) bacteria. Therefore, chitosan-pectin films with Fe3O4 magnetic nanoparticles provide promising results for active and intelligent food packaging applications.

Tuning the Magnetic Response of Magnetospirillum magneticum by Changing the Culture Medium: A Straightforward Approach to Improve Their Hyperthermia Efficiency.

Magnetotactic bacteria Magnetospirillum magneticum AMB-1 have been cultured using three different media: magnetic spirillum growth medium with Wolfe's mineral solution (MSGM + W), magnetic spirillum growth medium without Wolfe's mineral solution (MSGM - W), and flask standard medium (FSM). The influence of the culture medium on the structural, morphological, and magnetic characteristics of the magnetosome chains biosynthesized by these bacteria has been investigated by using transmission electron microscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. All bacteria exhibit similar average size for magnetosomes, 40-45 nm, but FSM bacteria present slightly longer subchains. In MSGM + W bacteria, Co2+ ions present in the medium substitute Fe2+ ions in octahedral positions with a total Co doping around 4-5%. In addition, the magnetic response of these bacteria has been thoroughly studied as functions of both the temperature and the applied magnetic field. While MSGM - W and FSM bacteria exhibit similar magnetic behavior, in the case of MSGM + W, the incorporation of the Co ions affects the magnetic response, in particular suppressing the Verwey (∼105 K) and low temperature (∼40 K) transitions and increasing the coercivity and remanence. Moreover, simulations based on a Stoner-Wolhfarth model have allowed us to reproduce the experimentally obtained magnetization versus magnetic field loops, revealing clear changes in different anisotropy contributions for these bacteria depending on the employed culture medium. Finally, we have related how these magnetic changes affect their heating efficiency by using AC magnetometric measurements. The obtained AC hysteresis loops, measured with an AC magnetic field amplitude of up to 90 mT and a frequency, f, of 149 kHz, reveal the influence of the culture medium on the heating properties of these bacteria: below 35 mT, MSGM - W bacteria are the best heating mediators, but above 60 mT, FSM and MSGM + W bacteria give the best heating results, reaching a maximum heating efficiency or specific absorption rate (SAR) of SAR/f ≈ 12 W g-1 kHz-1.

Structure and Properties of Copper Pyrophosphate by First-Principle Calculations.

Investigated the structural, electronic, and magnetic properties of copper pyrophosphate dihydrate (CuPPD) by the first-principle calculations based on the density functional theory (DFT). Simulations were performed with the generalized gradient approximation (GGA) of the exchange-correlation functional (Exc) supplemented by an on-site Coulomb self-interaction (U-Hubbard term). It was confirmed that the GGA method did not provide a satisfactory result in predicting the electronic energy band gap width (Eg) of the CuPPD crystals. Simultaneously, we measured the Eg of CuPPD nanocrystal placed inside mesoporous silica using the ultraviolet-visible spectroscopy (UV-VIS) technique. The proposed Hubbard correction for Cu-3d and O-2p states at U = 4.64 eV reproduces the experimental value of Eg = 2.34 eV. The electronic properties presented in this study and the results of UV-VIS investigations likely identify the semiconductor character of CuPPD crystal, which raises the prospect of using it as a component determining functional properties of nanomaterials, including quantum dots.

Magnetic Testis Targeting and Magnetic Hyperthermia for Noninvasive, Controllable Male Contraception via Intravenous Administration.

Mild testicular hyperthermia by the photothermal effect of gold nanorods could realize controllable male contraception. However, associated limitations, such as testicular administration and infrared laser inflicting severe pain, and the nondegradability of nanoparticles potentially causing toxicity, have restricted further clinical application. Inspired by the excellent physicochemical properties of iron oxide nanoparticles (IONPs), and the finding that testicular injection of PEG-coated IONPs with a diameter of 50 nm (PEG@Fe3O4-50) following an alternating magnetic field (AMF) could achieve controllable male contraception; here we propose a noninvasive, targeting approach for male contraception via intravenous administration. The magnetic properties and testes targeting of IONPs were proven to be greatly affected by their surface chemistry and particle size. After systemic administration, citric acid stabilized IONPs with size of 100 nm (CA@Fe3O4-100) were found to be the best ideal thermoagent for realizing the noninvasive contraception. This study offers new strategies for male contraception.

Magnetic nanoparticle decorated anodic alumina nanotubes for fluorescent detection of cathepsin B.

In this work, we present the process to provide anodic alumina nanotubes with magnetic responsivity based on magnetic nanoparticles. We demonstrate the possibility to cause the motion of these composite nanotubes under magnetic field, providing them with guided mobility. The obtained magnetic anodic alumina nanotubes are completely characterized and their potential to undergo selective and effective functionalization, and stimuli-responsive load release is demonstrated. For this purpose, protease-triggered release of fluorescent molecules loaded inside the magnetic anodic alumina nanotubes (MAANTs) by selective functionalization is performed. The inner walls of the MAANTs were selectively covered with protein padding of albumin-fluorescein isothiocyanate conjugate (FITC-BSA) through means of silanization. Protein functionalization was designed to undergo proteolytic hydrolysis in presence of cathepsin B- protease highly expressed during growth and initial stages of tumor metastasis - in order to cleave peptide bond of albumin and release fluorescent fragments of the protein. Proteolytic reaction with the enzyme is performed under acidic conditions. Presented arrangement is an exemplary combination of functionalities - which are vast - and of value for applications like drug delivery and biosensing applications.

Chitosan-polyvinylpyrrolidone CoxFe3-xO4 (0.25 ≤ x ≤ 1) nanoparticles for hyperthermia applications.

Blends of chitosan (CS) and polyvinylpyrrolidone (PVP) with cobalt ferrite nanoparticles (CoFe2O4) have the potential for use in several biomedical applications as drug delivery systems and for hyperthermia applications. Herein, we present a detailed study of the effect of chitosan and PVP on the structural, magnetic and specific absorption rate (SAR) properties of CoxFe3-xO4 (x = 0.25, 0.50, 0.75 and 1.00) as an effective heat nanomediator for hyperthermia. Structural characterization was carried out using X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Magnetic properties as a function of the Co2+ content were studied using a vibrating sample magnetometer (VSM) at room temperature. Hyperthermia investigations were performed at 454 ±â€¯20 kHz with a magnetic field amplitude of 5.5 mT. CS-PVP coated nanoparticles at x = 1.00 show a maximum SAR of 386 W/g, while bare nanoparticles show a SAR of 270 W/g. The advantage of the designed nanoparticles coated system lies in the fact that the versatile blending of chitosan and PVP enhance the SAR properties for hyperthermia of cobalt ferrite nanoparticles and provide biocompatibility and stability to the samples.

Synthesis of Dy-Y co-substituted manganese­zinc spinel nanoferrites induced anti-bacterial and anti-cancer activities: Comparison between sonochemical and sol-gel auto-combustion methods.

This study described the beneficial properties of ultrasonic irradiation approach to synthesize the spinel-type Dy-Y co-substituted Mn-Zn nanospinel ferrites (NSFs). We have used two different approaches like citrate sol-gel combustion and ultrasonic irradiation routes to produced series of Mn0.5Zn0.5Fe2-2x(DyxYx)O4 (0.0 ≤ x ≤ 0.05) NSFs (DyY-MnZn NSFs). The structure and morphology of NSFs X-was examined by using XRD, EDX, SEM and TEM methods. We have found that spinel ferrites and hematite phase in DyY-MnZn NSFs produced by citrate sol-gel, while DyY-MnZn NSFs created by ultrasonic irradiation contain a pure phase of spinel ferrite. TEM analysis revealed the spherical nanoparticles with fairly uniform size. We have also analyzed the biological applications of DyY-MnZn NSFs prepared by both methods (ultrasonication and sol-gel) by examining their anti-cancer and anti-bacterial (Escherichia coli and Staphylococcus aureu) activities. We have found that both methods produced inhibitory actions on colon cancer cells (HCT-116) and bacterial cells, whereas, no inhibitory action was observed when examined on normal and non-cancerous cells (HEK-293).

A CuII complex with an carbamoylcyanonitrosomethanide ligand formed in situ by the nucleophilic addition of water to dicyanonitrosomethanide: structure, spectral and magnetic properties.

The complex (2,2'-biquinoline-κ2N,N')(carbamoylcyanonitrosomethanide-κ2N,O)chloridocopper(II) acetonitrile monosolvate, [Cu(C3H2N3O2)Cl(C18H12N2)]·CH3CN or [Cu(ccnm)Cl(biq)]·acn (acn is acetonitrile, biq is 2,2'-biquinoline and ccnm is carbamoylcyanonitrosomethanide), (I), was prepared as a result of nucleophilic addition of water to the dicyanonitrosomethanide ion in the presence of CuII and biq. IR spectroscopy confirmed the presence of ccnm, biq and acn in (I). The solid-state structure consists of the neutral complex containing ccnm and biq ligands, coordinated to the CuII atom in a bidendate chelating manner, and a chloride ligand, resulting in a distorted tetragonal pyramidal coordination of CuII. The asymmetric unit is supplemented by one molecule of solvated acn which, along with the nitrile group of ccnm, serves as an acceptor in intermolecular hydrogen bonding, creating infinite chains along the b axis. Magnetic measurements revealed a paramagnetic behaviour with a very small Weiss temperature Θ = -0.32 K and high anisotropy of the g tensor (gx = 2.036, gy = 2.120 and gz = 2.205).

Multi-functional magnetic nanoparticles as an effective drug carrier for the controlled anti-tumor treatment.

Because of the complications and mutability of cancers, combination of chemotherapy and other therapy with multi-mechanisms would be a bright future for the treatment of cancer. Thus, development of multi-functional tumor-targeted drug delivery systems with two or more than two functions should be of great significance. In the study, the Fe3O4@C nanoparticles linked with thermoresponsive copolymer (MTC-NPs) were synthesized, after that, the magnetic properties and photothermal effects of MTC NPs were evaluated. Compared to the pure water, MTC-NPs absorbed more energy and transform it into heat under the 808 nm laser irradiation, and the temperature could increase over 60℃. In addition, the grafted copolymer with coil-to-globule transition acts as a gatekeeper for the temperature-controlled release of mitoxantrone molecules. The super paramagnetic behavior of MTC-NPs certified by the hysteresis loop gives a negligible coercivity at room temperature. Both in vitro and in vivo studies confirmed that the synergistic combination of magnetic targeting, drug controlled release, and thermochemotherapy improve the anti-tumor efficacy with lower side effects. This nanoparticle is a great potential drug carrier in anti-tumor drugs, which can improve the effect of hyperthermia, increase target distribution in tumor, and enhance curative effect for tumor while reducing normal tissue toxicity.

Polyphenol-Inspired Facile Construction of Smart Assemblies for ATP- and pH-Responsive Tumor MR/Optical Imaging and Photothermal Therapy.

Smart assemblies have attracted increased interest in various areas, especially in developing novel stimuli-responsive theranostics. Herein, commercially available, natural tannic acid (TA) and iron oxide nanoparticles (Fe3 O4 NPs) are utilized as models to construct smart magnetic assemblies based on polyphenol-inspired NPs-phenolic self-assembly between NPs and TA. Interestingly, the magnetic assemblies can be specially disassembled by adenosine triphosphate, which shows a stronger affinity to Fe3 O4 NPs than that of TA and partly replaces the surface coordinated TA. The disassembly can further be facilitated by the acidic environment hence causing the remarkable change of the transverse relaxivity and potent "turn-on" of fluorescence (FL) signals. Therefore, the assemblies for specific and sensitive tumor magnetic resonance and FL dual-modal imaging and photothermal therapy after intravenous injection of the assemblies are successfully employed. This work not only provides understandings on the self-assembly between NPs and polyphenols, but also will open new insights for facilely constructing versatile assemblies and extending their biomedical applications.

Contrasting Structural Reconstructions, Electronic Properties, and Magnetic Orderings along Different Edges of Zigzag Transition Metal Dichalcogenide Nanoribbons.

Two-dimensional transition metal dichalcogenides represent an emerging class of layered materials exhibiting various intriguing properties, and integration of such materials for potential device applications will necessarily invoke further reduction of their dimensionality. Using first-principles approaches, here we investigate the structural, electronic, and magnetic properties along the two different edges of zigzag MX2 (M = Mo, W; X = S, Se) nanoribbons. Along the M edges, we reveal a previously unrecognized but energetically strongly preferred (2 × 1) reconstruction pattern, which is universally operative for all the four systems (and possibly more), characterized by an elegant self-passivation mechanism through place exchanges of the outmost X and M edge atoms. In contrast, the X edges undergo a much milder (2 × 1) or (3 × 1) reconstruction for MoX2 or WX2, respectively. These contrasting structural preferences of the edges can be exploited for controlled fabrication of properly tailored transition metal dichalcogenide nanoribbons under nonequilibrium growth conditions. We further use the zigzag MoX2 nanoribbons to demonstrate that the Mo and X edges possess distinctly different electronic and magnetic properties, which are significant for catalytic and spintronic applications.

Unconventional Magnetic and Resistive Hysteresis in an Iodine-Bonded Molecular Conductor.

Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine-bonded molecular conductor (DIETSe)2 FeBr2 Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin-flop transition. Utilizing a mixed-anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties.

Synthesis and characterization of a uranium(II) monoarene complex supported by δ backbonding.

The low-temperature (<-35 °C) reduction of the trivalent uranium monoarene complex [{((Ad,Me) ArO)3 mes}U] (1), with potassium spheres in the presence of a slight excess of 2.2.2-cryptand, affords the quantitative conversion of 1 into the uranium(II) monoarene complex [K(2.2.2-crypt)][(((Ad,Me) ArO)3 mes)U] (1-K). The molecular and electronic structure of 1-K was established experimentally by single-crystal X-ray diffraction, variable-temperature (1) H NMR and X-band EPR spectroscopy, solution-state and solid-state magnetism studies, and optical absorption spectroscopy. The electronic structure of the complex was further investigated by DFT calculations. The complete body of evidence confirms that 1-K is a uranium(II) monoarene complex with a 5f (4) electronic configuration supported by δ backbonding and that the nearly reversible, room-temperature reduction observed for 1 at -2.495 V vs. Fc/Fc(+) is principally metal-centered.

A magnetic ionic liquid based on tetrachloroferrate exhibits three-dimensional magnetic ordering: a combined experimental and theoretical study of the magnetic interaction mechanism.

A new magnetic ionic liquid (MIL) with 3D antiferromagnetic ordering has been synthetized and characterized. The information obtained from magnetic characterization was supplemented by analysis of DFT calculations and the magneto-structural correlations. The result gives no evidence for direct iron-iron interactions, corroborating that the 3D magnetic ordering in MILs takes place via super-exchange coupling containing two diamagnetic atoms intermediaries.

DNA as a molecular local thermal probe for the analysis of magnetic hyperthermia.

Too hot to handle: The surroundings of magnetic nanoparticles can be heated by applying a magnetic field. Polymer-coated magnetic nanoparticles were functionalized with single-stranded DNA molecules and further hybridized with DNA modified with different fluorophores. By correlating the denaturation profiles of the DNA with the local temperature, temperature gradients for the vicinity of the excited nanoparticles were determined.

Magnetic Interactions as Supramolecular Function: Structure and Magnetic Properties of Hydrogen-Bridged Dinuclear Copper(II) Complexes.

The self-complementary coordination unit [Cu(H2 sabhea)]+ with a pentadentate amino alcohol as ligand enables the synthesis of the first triply hydrogen-bridged dinuclear copper(II) complex. Proton transfer allows the reversible transformation between this triply and the corresponding doubly hydrogen-bridged form. Despite the very short hydrogen bond found for the triply bridged complex, its exchange coupling constant is much smaller than that for the doubly bridged complex. H3 sabhea=N-salicylidene-2-(bis(2-hydroxyethyl)amino)ethyl amine.