Avrami behavior of magnetite nanoparticles formation in co-precipitation process

In this work, magnetite nanoparticles (mean particle size about 20 nm) were synthesized via coprecipitation method. In order to investigate the kinetics of nanoparticle formation, variation in the amount of reactants within the process was measured using pH-meter and atomic absorption spectroscopy (AAS) instruments. Results show that nanoparticle formation behavior can be described by Avrami equations. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to study the chemical and morphological characterization of nanoparticles. Some simplifying assumptions were employed for estimating the nucleation and growth rate of magnetite nanoparticles

Modeling for Superheating Phenomenon of Embedded Superfine Metallic Nanoparticles

Abstract A theoretical model is proposed to predict the size-dependency of melting point for embedded nanoparticles (NPs) by employing surface and interior average coordination number, cohesive energy and atomic bond strength. The model was applied on the perfect clusters of icosahedral (IC) and body centered tetragonal (BCT) without any vacancies and defects. The predicted results for superfine NPs (lower than 50 nm) of In, Ag, Sn and Pb were consistent with experimental results

PLGA/TiO2 nanocomposite scaffolds for biomedical applications: fabrication, photocatalytic, and antibacterial properties

Introduction: Porous 3D scaffolds synthesized using biocompatible and biodegradable materials could provide suitable microenvironment and mechanical support for optimal cell growth and function. The effect of the scaffold porosity on the mechanical properties, as well as the TiO2 nanoparticles addition on the bioactivity, antimicrobial, photocatalytic, and cytotoxicity properties of scaffolds were investigated. Methods: In the present study, porous scaffolds consisting poly (lactide-co-glycolide) (PLGA) containing TiO2 nanoparticles were fabricated via air-liquid foaming technique, which is a novel method and has more advantages due to not using additives for nucleation compared to former ways. Results: Adjustment of the foaming process parameters was demonstrated to allow for textural control of the resulting scaffolds and their pore size tuning in the range of 200–600 μm. Mechanical properties of the scaffolds, in particular, their compressive strength, revealed an inverse relationship with the pore size, and varied in the range of 0.97–0.75 MPa. The scaffold with the pore size 270 μm, compressive strength 0.97 MPa, and porosity level 90%, was chosen as the optimum case for the bone tissue engineering (BTE) application. Furthermore, 99% antibacterial effect of the PLGA/10 wt.% TiO2 nanocomposite scaffolds against the strain was achieved using Escherichia coli. Besides, no negative effect of the new method was observed on the bioactivity behavior and apatite forming ability of scaffolds in the simulated body fluid (SBF). This nanocomposite also displayed a good cytocompatibility when assayed with MG 63 cells. Lastly, the nanocomposite scaffolds revealed the capability to degrade methylene blue (MB) dye by nearly 90% under the UV irradiation for 3 hours. Conclusion: Based on the results, nanocomposite new scaffolds are proposed as a promising candidate for the BTE applications as a replacement for the previous ones

The effect of superparamagnetic iron oxide nanoparticles surface engineering on relaxivity of magnetoliposome

The purpose of this work is evaluating the effect of ultra small superparamagnetic iron oxide nanoparticles (USPIONs) coatings on encapsulation efficiency in liposomes and cellular cytotoxicity assay. Moreover, we assessed the effects of surface engineering on the relaxivity of magnetoliposome nanoparticles in order to create a targeted reagent for the intelligent diagnosis of cancers by MRI. For estimating the effect of nanoparticle coatings on encapsulation, several kinds of USPIONs coated by dextran, PEG5000 and citrate were used. All kinds of samples are monodispersed and below 100 ± 10 nm and the coatings of USPIONs have no significant effect on magnetoliposome diameter. The coating of USPIONs could have effect on percentage of encapsulation. The dextran coated USPIONs have more stability and quality accordingly the encapsulation increased up to 92, then the magnetoliposome nano particles have been targeted by Herceptin and anti-HER2 VHH, separately. Over storage period of four weeks the resulting particles were stable and physico-chemical properties such as size and zetapotential did not show any significant changes. The relaxivity of contrast agents was measured using a 1.5 T MRI. The r2/r1 ratio was more than two for all samples which demonstrate the negative contrast enhancing of all SPION embedded specimens. The high ratio of r2/r1 as well as high r2 is the best combination of a negative contrast agent as it is obtained for pure magnetite. The value of r2/r1 for all other samples including Herceptin targeted magnetoliposome, anti-HER2 VHH targeted magnetoliposome and non-targeted magnetoliposome were between ~21 to ~28, which show the magnetite embedded samples have enough negative contrast to be detectable by MRI. Therefore the HER2 targeted magnetoliposomes are a good and stable candidate as contrast agents in clinical radiology and biomedical research with minimal cytotoxicity and biocompatibility effects. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd

Dip coating of silica layer on melt-spun Finemet ribbons: surface morphology and electrical resistivity changes

In this study, melt-spun Finemet ribbons were coated by a thin layer of SiO2 using dip coating method. Amorphous ribbon prepared by melt spinning method and dip coating were done by using a solution of tetraethylen orthosilicate as a SiO2 precursor, ethanol as solvent and distilled water for hydrolysis. Different thicknesses of SiO2 layer, namely 304, 349, 451, 526 and 970 nm were obtained proportional to the number of dipping. Surface morphology and chemical composition of the coatings were analyzed by using Scanning Electron Microscope equipped with an energy dispersive spectroscope. The results clearly verified the presence of Si and O elements and confirmed the presence of silica layer on the surface of all coated ribbons. Microstructure and surface morphology of samples showed a smooth and brittle layer. Electrical resistivity of the samples was measured with a standard four-point probe device. The results confirmed an intense in increase of resistivity. Average value of electrical resistivity for coated samples was around 104 Ω-m compared to 10-6 Ω-m for Finemet ribbons. Capacity of the samples was evaluated by electronic parameter analyzer device in two different frequencies of 100 kHz and 1000 kHz. Impedance measurements of coated samples in 100 and 1000 kHz showed an increase about 70 and 10 times respectively

Controlled temperature-mediated curcumin release from magneto-thermal nanocarriers to kill bone tumors

Systemic chemotherapy has lost its position to treat cancer over the past years mainly due to drug resistance, side effects, and limited survival ratio. Among a plethora of local drug delivery systems to solve this issue, the combinatorial strategy of chemo-hyperthermia has recently received attention. Herein we developed a magneto-thermal nanocarrier consisted of superparamagnetic iron oxide nanoparticles (SPIONs) coated by a blend formulation of a three-block copolymer Pluronic F127 and F68 on the oleic acid (OA) in which Curcumin as a natural and chemical anti-cancer agent was loaded. The subsequent nanocarrier SPION@OA-F127/F68-Cur was designed with a controlled gelation temperature of the shell, which could consequently control the release of curcumin. The release was systematically studied as a function of temperature and pH, via response surface methodology (RSM). The bone tumor killing efficacy of the released curcumin from the carrier in combination with the hyperthermia was studied on MG-63 osteosarcoma cells through Alamar blue assay, live-dead staining and apoptosis caspase 3/7 activation kit. It was found that the shrinkage of the F127/F68 layer stimulated by elevated temperature in an alternative magnetic field caused the curcumin release. Although the maximum release concentration and cell death took place at 45 °C, treatment at 41 °C was chosen as the optimum condition due to considerable cell apoptosis and lower side effects of mild hyperthermia. The cell metabolic activity results confirmed the synergistic effects of curcumin and hyperthermia in killing MG-63 osteosarcoma cells

Particulate 3D Hydrogels of Silk Fibroin-Pluronic to Deliver Curcumin for Infection-Free Wound Healing

Skin is the largest protective tissue of the body and is at risk of damage. Hence, the design and development of wound dressing materials is key for tissue repair and regeneration. Although silk fibroin is a known biopolymer in tissue engineering, its degradation rate is not correlated with wound closure rate. To address this disadvantage, we mimicked the hierarchical structure of skin and also provided antibacterial properties; a hydrogel with globular structure consisting of silk fibroin, pluronic F127, and curcumin was developed. In this regard, the effect of pluronic and curcumin on the structural and mechanical properties of the hydrogel was studied. The results showed that curcumin affected the particle size, crystallinity, and ultimate elongation of the hydrogels. In vitro assays confirmed that the hydrogel containing curcumin is not cytotoxic while the diffused curcumin and pluronic provided a considerable bactericidal property against Methicillin-resistant Staphylococcus aureus. Interestingly, presence of pluronic caused more than a 99% reduction in planktonic and adherent bacteria in the curcumin-free hydrogel groups. Moreover, curcumin improved this number further and inhibited bacteria adhesion to prevent biofilm formation. Overall, the developed hydrogel showed the potential to be used for skin tissue regeneration

A new approach for calculation of relaxation time and magnetic anisotropy of ferrofluids containing superparmagnetic nanoparticles

In this work, a new approach is described for the calculation of the relaxation time and magnetic anisotropy energy of magnetic nanoparticles. Ferrofluids containing monodispersed magnetite nanoparticles were synthesized via hydrothermal method and then heated using the 10 kA/m external AC magnetic fields in three different frequencies: 10, 50 and 100 kHz. By measuring the temperature variations during the application of the magnetic field, the total magnetic time constant including both Brownian and Neel relaxation times can be calculated. By measuring the magnetic core size and hydrodynamic size of particles, the magnetic anisotropy can be calculated too. Synthesized ferrofluids were characterized via TEM, XRD, VSM and PCS techniques and the results were used for the mentioned calculations

A novel pathway to produce biodegradable and bioactive PLGA/TiO2 nanocomposite scaffolds for tissue engineering: Air�liquid foaming

Poly (lactate-co-glycolate) (PLGA) is a typical biocompatible and biodegradable synthetic polymer. The addition of TiO2 nanoparticles has shown to improve compressive modulus of PLGA scaffolds and reduced fast degradation. A novel method has been applied to fabricate PLGA/TiO2 scaffolds without using any inorganic solvent, with aim of improving the biocompatibility, macroscale morphology, and well inter-connected pores efficacy: Air�Liquid Foaming. Field Emission Scanning Electron Microscopy (FESEM) revealed an increase in interconnected porosity of up to 98. As well the compressive testing showed enhancement in modulus. Bioactivity and in vitro degradation were studied with immersion of scaffolds in Simulated Body Fluid (SBF) and incubation in Phosphate Buffered Saline (PBS), respectively. Formation of apatite layer corroborated the bioactivity after soaking in SBF. Degradation rate of scaffolds was increased with excessive addition of TiO2 contents withal. The in vitro cultured human-like MG63 ostoblast cells showed attachment, proliferation, and nontoxcitiy in contact, using MTT assay 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide. According to the results, the novel method utilized in this study generated porous viable tissue without using any inorganic solvent or porogen can be a promising candidate in further treatment of orthopedic patients effectively. © 2020 Wiley Periodicals, Inc