Microwave-Assisted Silanization of Magnetite Nanoparticles Pre-Synthesized by a 3D Microfluidic Platform.

Magnetite nanoparticles (Fe3O4 NPs) are among the most investigated nanomaterials, being recognized for their biocompatibility, versatility, and strong magnetic properties. Given that their applicability depends on their dimensions, crystal morphology, and surface chemistry, Fe3O4 NPs must be synthesized in a controlled, simple, and reproducible manner. Since conventional methods often lack tight control over reaction parameters and produce materials with unreliable characteristics, increased scientific interest has been directed to microfluidic techniques. In this context, the present paper describes the development of an innovative 3D microfluidic platform suitable for synthesizing uniform Fe3O4 NPs with fine-tuned properties. On-chip co-precipitation was performed, followed by microwave-assisted silanization. The obtained nanoparticles were characterized from the compositional and microstructural perspectives by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, supplementary physicochemical investigations, such as Fourier Transform Infrared Spectroscopy (FT-IR), Kaiser Test, Ultraviolet-Visible (UV-Vis) Spectrophotometry, Dynamic Light Scattering (DLS), and Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) analyses, demonstrated the successful surface modification. Considering the positive results, the presented synthesis and functionalization method represents a fast, reliable, and effective alternative for producing tailored magnetic nanoparticles.

U(VI) removal from diluted aqueous systems by sorption-flotation.

The legacies of past uranium mining and milling activities for nuclear fuel fabrication continue to be a cause of concern and require assessment and remedial action for researchers worldwide. The discharge of uranium contaminated water into the environment is a matter of regulation (World Health Organization, WHO-15 µg/L, Romanian Legislation, RO-21 µg/L), environment and health. Therefore, various removal technologies of U(VI) from diluted aqueous solutions include chemical precipitation, ion exchange, adsorption, immobilization on zero-valent iron nanoparticles, etc. have been extensively applied. Our previous research has studied the removal of U(VI) from diluted aqueous systems such as mine waters using Fe0-based nanomaterials synthesized in the laboratory (NMS) (Crane et al. in Water Res 45:2391-2942, 2011). The carbonate rich aqueous system was treated with NMS to remove U(VI). It was observed that after half an hour of reacting time only about 50% was removed due to its high tendency to form stable soluble carbonated complexes. Considering that, the present article aims to investigate the Sorption/Flotation technique, by using a sorbent generated in situ Fe2O3· nH2O and sodium oleate surfactant to remove U(VI) from diluted aqueous systems and to update the knowledge on the mechanism of process. In order to determine the removal efficiency of U(VI), the influencing factors were studied: pH, sorbent dose, surfactant concentration, contact time, stirring rate, the U(VI) concentration, air pressure in pressurized water recipient, and the effect of some accompanying heavy metals ions (Cu(II), Cr(VI), and Mo(VI)). The removal efficiency (%R) was monitored and its maximum values allowed to establish the optimal separation parameters (the established process parameters), which were validated on real mine water samples (MW). High U (VI) removal efficiencies %R > 98% were obtained. The Sorption/ Flotation technique was applied to remove U(VI) from two types of real mine water samples, namely "simple" and "pre-treated with NMS", respectively. For the mine water samples pre-treated with NMS, it worked in two variants: with and without pH correction. For pH range = 7.5-9.5, molar ratios [U(VI)] : [Fe(III)] = 1 : 75, [U(VI)] : [NaOL] = 1 : 1 × 10-2, contact time 30 min., stirring speed 250 RPM, initial concentration of U(VI) 10 mg·L-1, air pressure in pressurized water recipient p = 4 × 105 N·m-2 is obtained %R > 98%. It has been found that Sorption / Flotation can function with good %R values as a stand-alone operation or in tandem with NMS pre-treatment of mine water and pH adjustment proved to be highly efficiency (CU(VI) < 1·10-3 mg·L-1).

Fly-Ash Evaluation as Potential EOL Material Replacement of Cement in Pastes: Morpho-Structural and Physico-Chemical Properties Assessment.

The main objective of the study was to produce alternative binder materials, obtained with low cost, low energy consumption, and low CO2 production, by regenerating end-of-life (EOL) materials from mineral deposits, to replace ordinary Portland cement (OPC). The materials analyzed were ash and slag from the Turceni thermal power plant deposit, Romania. These were initially examined for morphology, mineralogical composition, elemental composition, degree of crystallinity, and heating behavior, to determine their ability to be used as a potential source of supplementary cementitious materials (SCM) and to establish the activation and transformation temperature in the SCM. The in-situ pozzolanic behavior of commercial cement, as well as cement mixtures with different percentages of ash addition, were further observed. The mechanical resistance, water absorption, sorptivity capacity, resistance to alkali reactions (ASR), corrosion resistance, and resistance to reaction with sulfates were evaluated in this study using low-vacuum scanning electron microscopy.

Dextran-Coated Iron Oxide Nanoparticles Loaded with Curcumin for Antimicrobial Therapies.

The current trend in antimicrobial-agent development focuses on the use of natural compounds that limit the toxicity of conventional drugs and provide a potential solution to the antimicrobial resistance crisis. Curcumin represents a natural bioactive compound with well-known antimicrobial, anticancer, and antioxidant properties. However, its hydrophobicity considerably limits the possibility of body administration. Therefore, dextran-coated iron oxide nanoparticles can be used as efficient drug-delivery supports that could overcome this limitation. The iron oxide nanoparticles were synthesized through the microwave-assisted hydrothermal method by varying the treatment parameters (pressure and reaction time). The nanoparticles were subsequently coated with dextran and used for the loading of curcumin (in various concentrations). The drug-delivery systems were characterized through X-ray diffraction (XRD) coupled with Rietveld refinement, transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), selected area electron diffraction (SAED), dynamic light scattering (DLS) and zeta potential, thermogravimetry and differential scanning calorimetry (TG-DSC), vibrating sample magnetometry (VSM), and UV-Vis spectrophotometry, as well as regarding their antimicrobial efficiency and biocompatibility using the appropriate assays. The results demonstrate a promising antimicrobial efficiency, as well as an increased possibility of controlling the properties of the resulted nanosystems. Thus, the present study represents an important step forward toward the development of highly efficient antimicrobial drug-delivery systems.

Melissa officinalis: Composition, Pharmacological Effects and Derived Release Systems-A Review.

Melissa officinalis is a medicinal plant rich in biologically active compounds which is used worldwide for its therapeutic effects. Chemical studies on its composition have shown that it contains mainly flavonoids, terpenoids, phenolic acids, tannins, and essential oil. The main active constituents of Melissa officinalis are volatile compounds (geranial, neral, citronellal and geraniol), triterpenes (ursolic acid and oleanolic acid), phenolic acids (rosmarinic acid, caffeic acid and chlorogenic acid), and flavonoids (quercetin, rhamnocitrin, and luteolin). According to the biological studies, the essential oil and extracts of Melissa officinalis have active compounds that determine many pharmacological effects with potential medical uses. A new field of research has led to the development of controlled release systems with active substances from plants. Therefore, the essential oil or extract of Melissa officinalis has become a major target to be incorporated into various controlled release systems which allow a sustained delivery.

Iron Oxide-Silica Core-Shell Nanoparticles Functionalized with Essential Oils for Antimicrobial Therapies.

Recent years have witnessed a tremendous interest in the use of essential oils in biomedical applications due to their intrinsic antimicrobial, antioxidant, and anticancer properties. However, their low aqueous solubility and high volatility compromise their maximum potential, thus requiring the development of efficient supports for their delivery. Hence, this manuscript focuses on developing nanostructured systems based on Fe3O4@SiO2 core-shell nanoparticles and three different types of essential oils, i.e., thyme, rosemary, and basil, to overcome these limitations. Specifically, this work represents a comparative study between co-precipitation and microwave-assisted hydrothermal methods for the synthesis of Fe3O4@SiO2 core-shell nanoparticles. All magnetic samples were characterized by X-ray diffraction (XRD), gas chromatography-mass spectrometry (GC-MS), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry and differential scanning calorimetry (TG-DSC), and vibrating sample magnetometry (VSM) to study the impact of the synthesis method on the nanoparticle formation and properties, in terms of crystallinity, purity, size, morphology, stability, and magnetization. Moreover, the antimicrobial properties of the synthesized nanocomposites were assessed through in vitro tests on Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. In this manner, this study demonstrated the efficiency of the core-shell nanostructured systems as potential applications in antimicrobial therapies.

MAPLE Coatings Embedded with Essential Oil-Conjugated Magnetite for Anti-Biofilm Applications.

The present study reports on the development and evaluation of nanostructured composite coatings of polylactic acid (PLA) embedded with iron oxide nanoparticles (Fe3O4) modified with Eucalyptus (Eucalyptus globulus) essential oil. The co-precipitation method was employed to synthesize the magnetite particles conjugated with Eucalyptus natural antibiotic (Fe3O4@EG), while their composition and microstructure were investigated using grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The matrix-assisted pulsed laser evaporation (MAPLE) technique was further employed to obtain PLA/Fe3O4@EG thin films. Optimal experimental conditions for laser processing were established by complementary infrared microscopy (IRM) and scanning electron microscopy (SEM) investigations. The in vitro biocompatibility with eukaryote cells was proven using mesenchymal stem cells, while the anti-biofilm efficiency of composite PLA/Fe3O4@EG coatings was assessed against Gram-negative and Gram-positive pathogens.

Multifunctional Platforms Based on Graphene Oxide and Natural Products.

Background and objectives: In the last few years, graphene oxide has attracted much attention in biomedical applications due to its unique physico-chemical properties and can be used as a carrier for both hydrophilic and/or hydrophobic biomolecules. The purpose of this paper was to synthesize graphene oxide and to obtain multifunctional platforms based on graphene oxide as a nanocarrier loaded with few biologically active substances with anticancer, antimicrobial or anti-inflammatory properties such as gallic acid, caffeic acid, limonene and nutmeg and cembra pine essential oils. Materials and Methods: Graphene oxide was obtained according to the method developed by Hummers and further loaded with biologically active agents. The obtained platforms were characterized using FTIR, HPLC, TGA, SEM, TEM and Raman spectroscopy. Results: Gallic acid released 80% within 10 days but all the other biologically active agents did not release because their affinity for the graphene oxide support was higher than that of the phosphate buffer solution. SEM characterization showed the formation of nanosheets and a slight increase in the degree of agglomeration of the particles. The ratio I2D/IG for all samples was between 0.18 for GO-cembra pine and 0.27 for GO-limonene, indicating that the GO materials were in the form of multilayers. The individual GO sheets were found to have less than 20 µm, the thickness of GO was estimated to be ~4 nm and an interlayer spacing of about 2.12 Å. Raman spectroscopy indicated that the bioactive substances were adsorbed on the surface and no degradation occurred during loading. Conclusions: These findings encourage this research to further explore, both in vitro and in vivo, the biological activities of bioactive agents for their use in medicine.

New Approach to Prepare Willow Bark Extract-Lipid Based Nanosystems with Enhanced Antioxidant Activity.

In this study the conventional oils used for lipid nanocarriers (NLCs) synthesis were replaced by high concentration of fish oils (e.g., fish oil concentrated in omega-3 fatty acids, fish oil enriched in omega-3 and omega-6 fatty acids and salmon oil), in order to produce appropriate lipid based nanosystems able to entrap willow bark extract (WBE). Formulation factors such as the nature of the fish oil, glycerol content and WBE loading were evaluated to produce optimum lipid based nanosystems with suitable physical stability and enhanced antioxidant activity. The synthesized WBE-NLC showed spherical and homogeneous particles and average diameters in the range of 200-250 nm, as determined by TEM measurements. The electrokinetic potentials were negative for all free- and WBE-loaded NLCs, with values between -29.1 ÷ - 35.8 mV, which reveal an excellent physical stability. By scanning calorimetry measurements it has been shown that the lipid crystallization and melting behavior of NLCs before and after loading with WBE were no significantly influenced by the type of fish oil used and only in a few NLCs formulations an obvious perturbation of lipid network have been detected. The chemiluminescence technique has been used to assess the effect of fish oil type on the in vitro antioxidant activity of WBE-NLCs. Ability of WBE entrapped within NLCs to scavange the free radicals was greater than for native WBE and fish oils. The difference between the antioxidant activity of WBE-NLC (98%) and those of pure WBE (AA% = 77.2) and fish oil (AA% = 83.7), may be explained by the occurrence of a synergistic effect between the components of lipid nanocarriers.