Performance evaluation of dextran-coated CaFe12O19/MnFe2O4 exchange-spring composites for the self-heating properties at radio frequency field.

The CaFe12O19/MnFe2O4 composites with the hard (CaFe12O19) and soft (MnFe2O4) magnetic phases, were prepared by chemical co-precipitation method. The prepared composites were calcined at three different temperatures to form different phases. The structural, morphological, and magnetic properties of composite were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), room temperature vibrational sample magnetometer (VSM), and transmission electron microscopy (TEM). The presence of the hard and soft phases has been confirmed without any secondary phase from XRD analysis, indicating the formation of composite. The crystallite size is found to be in the range of 24-44 nm calculated by Scherrer's formula. The TEM revealed hexagonal platelets of CaFe12O19 with spinel MnFe2O4 particles with an average particle size of 48 nm formed at the surface of the CaFe12O19/MnFe2O4 composite. The room temperature magnetic properties of composite were evaluated by employing VSM. The magnetic measurements have displayed enhancement in coercivity and magnetization for CaFe12O19/MnFe2O4, indicating that the composite possessed excellent exchange coupling. The composite's enhanced energy product ((BH)max) made it highly promising for biomedical applications such as hyperthermia. The exchange-spring coupled magnetic composite was coated with dextran to make it biocompatible, which is necessary for hyperthermia applications. The coating was confirmed using Fourier transform infrared spectroscopy (FTIR). Cytotoxicity tests on Vero cell lines showed that the coated composites had an excellent (>95%) cell survival rate. The hyperthermia heating of composite was measured for different concentrations of composite (0.25, 0.5, 1, 2, and 4 mg/mL) from which specific loss power (SLP) was calculated. From these SLP values, the optimized concentration was identified.

Superior Cyclic Stability and Capacitive Performance of Cation- and Water Molecule-Preintercalated δ-MnO2/h-WO3 Nanostructures as Supercapacitor Electrodes.

The large number of active sites in the layered structure of δ-MnO2 with considerable interlayer spacing makes it an excellent candidate for ion storage. Unfortunately, the δ-MnO2-based electrode has not yet attained the exceptional storage potential that it should demonstrate because of disappointing structural deterioration during periodic charging and discharging. Here, we represent that stable Na ion storage in δ-MnO2 may be triggered by the preintercalation of K ions and water molecules. Furthermore, the sluggish reaction kinetics and poor electrical conductivity of preintercalated δ-MnO2 layers are overcome by the incorporation of h-WO3 in the preintercalated δ-MnO2 to form novel composite electrodes. The composites contain mixed valence metals, which provide a great number of active sites along with improved redox activity, while maintaining a fast ion transfer efficiency to enhance the pseudocapacitance performance. Based on our research, the composite prepared from preintercalated δ-MnO2 with 5 wt % h-WO3 provides a specific capacitance of up to 363.8 F g-1 at a current density of 1.5 A g-1 and an improved energy density (32.3 W h kg-1) along with an ∼14% increase in capacity upon cycling up to 5000 cycles. Hence, the interaction between the preintercalated δ-MnO2 and h-WO3 nanorods results in satisfactory energy storage performance due to the defect-rich structure, high conductivity, superior stability, and lower charge transfer resistance. This research has the potential to pave the way for a new class of hybrid supercapacitors that could fill the energy gap between chemical batteries and ideal capacitors.

Evaluation of chitosan-Ag/TiO2 nanocomposite for the enhancement of shelf life of chili and banana fruits.

Post-harvest losses of fruits and vegetables account for a large share of food waste in the world due to improper handling and packaging. By using the sol-gel method, Ag/TiO2 nanocomposite was prepared in this study from micro-sized commercial TiO2 powder and incorporated in a chitosan-cellulose matrix for the purpose of promising food packaging. The particle size and distribution of Ag nanoparticles (9.2437 nm size) confirmed their successful inclusion in the TiO2 surface. The morphology of the package assured the successful and uniform disbursement of Ag/TiO2 nanocomposite into the chitosan-cellulose matrix, which led to enhanced water resistance and photocatalytic activity. The developed package is proficient in hindering the growth of fecal coliform bacteria (Esche (Escherichia coli) by 9 mm in the agar plate. Moreover, the efficient application of chitosan-Ag/TiO2 nanocomposite in food coating and packaging was examined in extending shelf life, minimizing water loss, and preventing microbial infection during the storage of chili (up to 7 days at 37 °C) and banana, respectively. It can be concluded from the results that chitosan-Ag/TiO2 nanocomposite-based food coating and packaging have competent potential for enhancing the shelf life of moist foods.

Progeny Transfer Effects of Chitosan-Coated Cobalt Ferrite Nanoparticles.

Cobalt ferrite nanoparticles (CFNs) are promising materials for their enticing properties for different biomedical applications, including magnetic resonance imaging (MRI) contrast, drug carriers, biosensors, and many more. In our previous study, a chitosan-coated CFN (CCN) nanocomplex demonstrated potential as an MRI contrast dye by improving the biocompatibility of CFN. In this study, we report the progeny transfer effects of CCN following a single intravenous injection of CCN (20, 40, or 60 mg/kg) in pregnant albino Wistar rats. Biochemical and histological observation reveals that CCN is tolerated with respect to maternal organ functions (e.g., liver, kidney). Atomic absorption spectroscopy results showed that CCN or CCN-leached iron could cross the placental barrier and deposit in the fetus. Furthermore, this deposition accelerated lipid peroxidation in the placenta and fetus.

Manganese Ferrite Nanoparticles (MnFe2O4): Size Dependence for Hyperthermia and Negative/Positive Contrast Enhancement in MRI.

We synthesized manganese ferrite (MnFe2O4) nanoparticles of different sizes by varying pH during chemical co-precipitation procedure and modified their surfaces with polysaccharide chitosan (CS) to investigate characteristics of hyperthermia and magnetic resonance imaging (MRI). Structural features were analyzed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), selected area diffraction (SAED) patterns, and Mössbauer spectroscopy to confirm the formation of superparamagnetic MnFe2O4 nanoparticles with a size range of 5-15 nm for pH of 9-12. The hydrodynamic sizes of nanoparticles were less than 250 nm with a polydispersity index of 0.3, whereas the zeta potentials were higher than 30 mV to ensure electrostatic repulsion for stable colloidal suspension. MRI properties at 7T demonstrated that transverse relaxation (T2) doubled as the size of CS-coated MnFe2O4 nanoparticles tripled in vitro. However, longitudinal relaxation (T1) was strongest for the smallest CS-coated MnFe2O4 nanoparticles, as revealed by in vivo positive contrast MRI angiography. Cytotoxicity assay on HeLa cells showed CS-coated MnFe2O4 nanoparticles is viable regardless of ambient pH, whereas hyperthermia studies revealed that both the maximum temperature and specific loss power obtained by alternating magnetic field exposure depended on nanoparticle size and concentration. Overall, these results reveal the exciting potential of CS-coated MnFe2O4 nanoparticles in MRI and hyperthermia studies for biomedical research.

Evaluation of a novel nanocrystalline hydroxyapatite powder and a solid hydroxyapatite/Chitosan-Gelatin bioceramic for scaffold preparation used as a bone substitute material.

Artificially fabricated hydroxyapatite (HAP) shows excellent biocompatibility with various kinds of cells and tissues which makes it an ideal candidate for a bone substitute material. In this study, hydroxyapatite nanoparticles have been prepared by using the wet chemical precipitation method using calcium nitrate tetra-hydrate [Ca(NO3)2.4H2O] and di-ammonium hydrogen phosphate [(NH4)2 HPO4] as precursors. The composite scaffolds have been prepared by a freeze-drying method with hydroxyapatite, chitosan, and gelatin which form a 3D network of interconnected pores. Glutaraldehyde solution has been used in the scaffolds to crosslink the amino groups (|NH2) of gelatin with the aldehyde groups (|CHO) of chitosan. The X-ray diffraction (XRD) performed on different scaffolds indicates that the incorporation of a certain amount of hydroxyapatite has no influence on the chitosan/gelatin network and at the same time, the organic matrix does not affect the crystallinity of hydroxyapatite. Transmission electron microscope (TEM) images show the needle-like crystal structure of hydroxyapatite nanoparticle. Scanning Electron Microscope (SEM) analysis shows an interconnected porous network in the scaffold where HAP nanoparticles are found to be dispersed in the biopolymer matrix. Fourier transforms infrared spectroscopy (FTIR) confirms the presence of hydroxyl group (OH-) , phosphate group (PO3- 4) , carbonate group (CO2- 3) , imine group (C=N), etc. TGA reveals the thermal stability of the scaffolds. The cytotoxicity of the scaffolds is examined qualitatively by VERO (animal cell) cell and quantitatively by MTTassay. The MTT-assay suggests keeping the weight percentage of glutaraldehyde solution lower than 0.2%. The result found from this study demonstrated that a proper bone replacing scaffold can be made up by controlling the amount of hydroxyapatite, gelatin, and chitosan which will be biocompatible, biodegradable, and biofriendly for any living organism.