Agglomeration of magnetic nanoparticles

Nanomaterials in electrochemical nanobiosensors of miRNAs

Nanomaterial-based biosensors have received significant attention owing to their unique properties, especially enhanced sensitivity. Recent advancements in biomedical diagnosis have highlighted the role of microRNAs (miRNAs) as sensitive prognostic and diagnostic biomarkers for various diseases. Current diagnostics methods, however, need further improvements with regards to their sensitivity, mainly due to the low concentration levels of miRNAs in the body. The low limit of detection of nanomaterial-based biosensors has turned them into powerful tools for detecting and quantifying these biomarkers. Herein, we assemble an overview of recent developments in the application of different nanomaterials and nanostructures as miRNA electrochemical biosensing platforms, along with their pros and cons. The techniques are categorized based on the nanomaterial used.

Characterization and Antibacterial Potential of Iron Oxide Nanoparticles in Eradicating Uropathogenic E. coli

Proper management and control measurements are needed to stop the spread of highly pathogenic E. coli isolates that cause urinary tract infections (UTI) by developing new antibacterial agents to ensure the safety of public health. Therefore, the present investigations were used to achieve the synthesis of iron oxide nanoparticles (IONPs) via a simple coprecipitation method using ferric nitrates Fe (NO3)3 as the precursor and hydrazine solution as the precipitator and to explore the antibacterial activity against eradicating Uropathogenic Escherichia coli (E. coli). The synthesized IONPs were further studied using a UV-vis spectrophotometer, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopic (SEM) analysis. The maximum surface plasmon resonance peak was observed as absorption at 320 nm in a colloidal solution to validate the synthesis of IONPs. The FT-IR analysis was used to identify different photoactive functional groups that were responsible for the reduction of Fe (NO3)3 to IONPs. The crystalline nature of synthesized IONPs was revealed by XRD patterns with an average particle size ranging as 29 nm. The SEM image was employed to recognize the irregular morphology of synthesized nanoparticles. Moreover, significant antibacterial activity was observed at 1 mg/mL stock solution but after (125, 250, and 500 μg/mL) dilution, the synthesized IONPs showed moderate activity and became inactive at lower concentrations. The morphological and biochemical tests were used to confirm the presence of E. coli in the samples. Furthermore, the minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) were carried out to determine the inhibitory concentrations for the isolated bacteria. The isolated E. coli were also subjected to antibiotic sensitivity testing that showed high resistance to antibiotics such as penicillin and amoxicillin. Thus, the findings of this study were to use IONPs against antibiotic resistance that has been developed in an inappropriate way.

Preparation of a 3D printable high-performance GelMA hydrogel loading with magnetic cobalt ferrite nanoparticles

Osteosarcoma remains a worldwide concern due to the poor effectiveness of available therapies in the clinic. Therefore, it is necessary to find a safe and effective therapy to realize the complete resection of osteosarcoma and reconstruction of the bone defect. Magnetic hyperthermia based on magnetic nanoparticles can kill tumor cells by raising the temperature without causing the side effects of conventional cancer treatments. This research aims to design a high-performance magnetic hydrogel composed of gelatin methacrylate and highly magnetic cobalt ferrite (CFO) nanoparticles for osteosarcoma treatment. Specifically, CFO is surface functionalized with methacrylate groups (MeCFO). The surface modified CFO has good biocompatibility and stable solution dispersion ability. Afterward, MeCFO nanoparticles are incorporated into GelMA to fabricate a three-dimensional (3D) printable MeCFO/GelMA magnetic hydrogel and then photocross-linked by UV radiation. MeCFO/GelMA hydrogel has high porosity and swelling ability, indicating that the hydrogel possesses more space and good hydrophily for cell survival. The rheological results showed that the hydrogel has shear thinning property, which is suitable as a bioprinting ink to produce desired structures by a 3D printer. Furthermore, 50 μg/mL MeCFO not only decreases the cell activity of osteosarcoma cells but also promotes the osteogenic differentiation of mBMSCs. The results of the CCK-8 assay and live/dead staining showed that MeCFO/GelMA hydrogel had good cytocompatibility. These results indicated that MeCFO/GelMA hydrogel with potential antitumor and bone reconstruction functions is a promising therapeutic strategy after osteosarcoma resection.

Fabrication and Characterization of W-Substituted ZnFe2O4 for Gas Sensing Applications

A sol–gel technique was successfully employed in creating pure and W-substituted zinc ferrite, with nominal compositions of ZnFe2−2xWxO4 (0.0 ≤ x ≤ 0.15). For the purposes of investigating the physical and chemical properties of the generated powders, several analytical techniques were used. In TEM images of all the compositions, mixed-shaped particles (cubic, spherical, and hexagonal) were observed. The crystallite size decreases from 82 nm (x = 0.0) to 32 nm (x = 0.15) with an increase in the W doping contents in the ZnFe2O4 lattice. The microstrain increases with increasing W doping content. Furthermore, the surface area of pure ZnFe2O4, 0.05 W-ZnFe2O4, 0.10 W-ZnFe2O4, and 0.15 W-ZnFe2O4 NPs were calculated as being 121.5, 129.1, 134.4 and 143.2 m2 g−1, respectively, with a mesoporous pore structure for all ferrite samples. The calculated BJH pore size distribution was within the range of 160 to 205 Å. All W-doped ZnFe2O4 samples show H-M loops with paramagnetic characteristics. The magnetization (M) directly increases by increasing the applied field (H) without achieving saturation up to 20 kA/m. For comparison, the magnetization at 20 kA/m gradually decreases with increasing W doping content. Among all the synthesized samples, the 0.15 W-ZnFe2O4 NPs demonstrated the highest sensitivity towards acetone gas at 350 °C.

The Synthesis Methodology and Characterization of Nanogold-Coated Fe3O4 Magnetic Nanoparticles

Core-shell nanostructures are widely used in many fields, including medicine and the related areas. An example of such structures are nanogold-shelled Fe₃O₄ magnetic nanoparticles. Systems consisting of a magnetic core and a shell made from nanogold show unique optical and magnetic properties. Thus, it is essential to develop the methodology of their preparation. Here, we report the synthesis methodology of Fe₃O₄@Au developed so as to limit their agglomeration and increase their stability. For this purpose, the impact of the reaction environment was verified. The properties of the particles were characterized via UV-Vis spectrophotometry, dynamic light scattering (DLS), X-ray diffraction (XRD), and Scanning Electron Microscopy-Energy Dispersive X-ray analysis (SEM-EDS technique). Moreover, biological investigations, including determining the cytotoxicity of the particles towards murine fibroblasts and the pro-inflammatory activity were also performed. It was demonstrated that the application of an oil and water reaction environment leads to the preparation of the particles with lower polydispersity, whose agglomerates’ disintegration is 24 times faster than the disintegration of nanoparticle agglomerates formed as a result of the reaction performed in a water environment. Importantly, developed Fe₃O₄@Au nanoparticles showed no pro-inflammatory activity regardless of their concentration and the reaction environment applied during their synthesis and the viability of cell lines incubated for 24 h with the particle suspensions was at least 92.88%. Thus, the developed synthesis methodology of the particles as well as performed investigations confirmed a great application potential of developed materials for biomedical purposes.

The Structure, Magnetic, and Gas Sensing Characteristics of W-Substituted Co-Ferrite Nanoparticles

Ferrites have been broadly investigated as gas sensors. The present article reports on the synthesis of Co-ferrite doped with W ions and their gas sensing abilities. A series of single phase CoFe2O4 powder with different W-doping (0.0 ≤ x ≤ 0.15) was synthesized using sol-gel synthesis. A variation in the saturation magnetization (Ms) and the lattice dimension with W(VI) substitution was associated with a change in the distribution of Fe(III) ions between tetrahedral and octahedral sites. Introducing W(VI) ions into the spinel lattice induced the rearrangement of Fe(III) ions. The total Ms increased with W-doping up to x = 0.05 (Ms = 50.1 Am2/kg) and it dramatically decreased to 34.6 Am2/kg with x = 0.15 of doping. However, the lattice parameter increased with increasing doping levels. Different W-doped CoFe2O4 were examined for a gas sensing response in the temperature range of 200–450 °C. Comparing the sensor responses to various reducing gases, the material’s response was shown to be sensitive and selective for acetone. The addition of W (0.15%) had a significant impact on the response and on the operating temperature of the sensor material, indicating that it might be used as an acetone sensor.

(Carboxymethyl-stevioside)-coated magnetic dots for enhanced magnetic hyperthermia and improved glioblastoma treatment

The use of different types of biomaterials as surfactant moities has a defined role in magnetic hyperthermia-mediated cancer therapy (MHCT). In this work, we present carboxymethyl-stevioside (CMS)-modified magnetic dots (MDs) as efficient magnetic hyperthermia agents for glioma therapy. The synthesized MDs with CMS biosurfactant coating exhibited significant water stability that resulted in a remarkable specific absorption rate of 209.25 W/g on application of alternating magnetic field of strength 359 kHz and 188 Oe. The MDs further demonstrated significant anti-migratory and anti-invasive effect on glioma C6 cells by inhibiting the gene expression of matrix metalloproteinases-2 and -9. The effect of immediate and long term hyperthermia treatment was then evaluated after repetitive exposure to hyperthermia, in terms of glioma cell viability, the effect of treatment on cell morphology, the cell cycle distribution and oxidative stress generation. The results obtained suggest the promising potential of CMS-modified nano-heaters for excellent magnetic hyperthermia-mediated glioma therapy.

Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions

We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m², could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.