Search Results (127)

The contamination of aquatic systems by industrial dyes, particularly methylene blue (MB), presents a significant environmental challenge due to their chemical stability and toxicity. In this study, the development and application of a novel magnetic nanohybrid comprising multiwall carbon nanotubes (MWCNTs) functionalized with maghemite (γ-Fe₂O₃) nanoparticles biosynthesized using Eucalyptus globulus extract (denoted MWNT-NPE) is reported. The material was thoroughly characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Vibrating Sample Magnetometer (VSM), and Fourier-Transform Infrared (FTIR) techniques, revealing high crystallinity, mesoporosity, and superparamagnetic behavior. The MWNT-NPE exhibited exceptional MB adsorption performance under optimized conditions (pH 6, 0.8 g L⁻¹ dose, 40 min equilibrium), achieving a maximum adsorption capacity of 92.9 mg g⁻¹. Kinetic analysis indicated chemisorption and physisorption regimes depending on MB concentration, with the pseudo-second-order and Freundlich isotherm models providing the best fits of experimental data. FTIR spectroscopy demonstrated that the removal mechanism involves π–π stacking, hydrogen bonding, and electrostatic interactions between MB molecules and the composite’s surface functional groups. Notably, the magnetic nanohybrid retained over 98% removal efficiency across five regeneration cycles and successfully removed MB from synthetic effluents with efficiencies exceeding 91%. These findings highlight the synergistic adsorption and magnetic recovery capabilities of the bio-functionalized hybrid system, presenting a sustainable, reusable, and scalable solution for industrial dye remediation. Full article

Nanotechnology, specifically magnetic nanoparticles (MNPs), is revolutionizing cancer treatment. Magnetic hyperthermia is a treatment that, using MNPs, can selectively kill cancer cells without causing damage to the surrounding tissues. Background/Objectives: This work aimed to analyze how the synthesis conditions, namely, how the pH of the reaction can influence the magnetic properties of Fe₃O₄ nanoparticles for magnetic hyperthermia, using the hydrothermal synthesis. Methods: For the hydrothermal synthesis, FeCl₃·6H₂O and FeCl₂·4H₂O were mixed with different quantities of NaOH to adjust the pH. After obtaining a black precipitate, the samples were placed in an autoclave at 200 °C for 60 h, followed by a washing and drying phase. The obtained MNPs were analyzed using X-Ray Diffraction (XRD), Transmission Electron Microscopy, a Superconducting Quantum Interference Device, Specific Absorption Rate analysis, and cytotoxicity assays. Results: Different MNPs were analyzed (9.06 < pH < 12.75). The XRD results showed the presence of various iron oxide phases (magnetite, maghemite, and hematite), resulting from the oxidization of the iron phases present in the autoclave. In terms of the average particle size, it was verified that, by increasing the pH value, the size decreases (from 53.53 nm to 9.49 nm). Additionally, MNPs possess a superparamagnetic behaviour with high SAR values (above 69.3 W/g). Conclusions: It was found that the pH of the reaction can influence the size, morphology, magnetization, and thermal efficiency of the MNP. The MNP with the highest composition of Fe₃O₄ was synthesized with a pH of 12.75, with a cubic morphology and a SAR value of 92.7 ± 3.2 W/g. Full article

This study focused on composites of magnetite magnetic nanoparticles (MNP) and poly(lactic acid) (PLA) prepared via sonochemical synthesis. The evaluation of MNP loadings (2, 5, 10, 15, and 20 wt.%) provided insights into the structural and reactivity properties of the materials. Methods used included XRD, FT-IR and Raman spectroscopy, SEM and TEM microscopy, textural and thermal analysis (TG and DTA), and magnetic property measurements. The agreement between theoretical and experimental MNP loadings was good. XRD patterns showed predominantly MNP and semicrystalline phases, with a minor maghemite phase detected by FT-Raman and magnetic measurements. FT-IR analysis revealed interactions between MNP and PLA, confirmed by thermal analysis showing higher transition temperatures for the composites (145 °C) compared to pure PLA (139 °C). FT-Raman spectra also indicated that PLA helps prevent iron oxide oxidation, enhancing nanoparticle stability. SEM and TEM micrographs showed well-dispersed, spherical nanoparticles with minimal agglomeration, dependent on MNP loading. The nanocomposites exhibited low N₂ adsorption, resulting in low surface area (~2.1 m²/g) and porosity (~0.03 cm³/g). Magnetic analysis indicated that in the 2MNP/PLA sample, MNP were in a superparamagnetic-like regime at 300 K, suggesting good dispersion of 2 wt.% MNP in the PLA matrix. Full article

Maghemite (γ-Fe₂O₃) nanoparticles are widely used in biomedical, catalytic, and environmental applications owing to their superparamagnetic properties and surface tunability. Functionalization with primary amine groups via 3-aminopropyltriethoxysilane (APTES) is commonly employed to enable the covalent immobilization of biomolecules and other functional species. The efficiency of this silanization process depends significantly on the density of surface hydroxyl groups, which serve as reactive sites for silane coupling. In this study, the impact of acid and base pretreatments on the surface hydroxylation of γ-Fe₂O₃ nanoparticles and the subsequent APTES grafting performance was systematically evaluated. Intermediate modification using tetraethoxysilane (TEOS) was explored as a strategy to enhance silanization by forming a hydroxyl-rich silica interlayer. Fourier transform infrared spectroscopy and zeta-potential measurements were performed to assess surface chemistry and functional-group incorporation. The results indicate that acid pretreatment significantly increases the availability of reactive –OH groups, while TEOS-assisted silanization improves the uniformity and density of surface-bound amine groups. These findings highlight the critical role of surface conditioning and sequential modification in achieving the controlled and robust amine functionalization of iron oxide nanoparticles. The developed approach provides a foundation for the rational design of surface engineering protocols for high-performance magnetic nanomaterials. Full article

Administration of monocyte-derived dendritic cells (moDCs) sensitized by cancer-associated antigens to the patient is applied to boost the T-cell mediated anti-tumor immune response. Loading moDCs with magnetic nanoparticles (MNPs) and controlling their migration to lymph nodes by an external magnetic field is a way to improve the effectiveness of immunotherapy. In this study, spherical MNPs of maghemite iron oxide with a diameter of about 14 nm were synthesized by laser target evaporation method (LTE) and examined in the context of their prospective use for the needs of moDCs immunotherapy. Characterization of the physicochemical properties of MNPs and their stabilization in physiological media, as well as the magnetic properties of MNPs in the suspensions were considered in detail. The cytotoxic effect of MNPs in growth medium on the human moDCs and MNPs uptake by the cells were also estimated. We show that up-taken MNPs and MNPs in growth medium demonstrated cytotoxic effect only at high concentrations. At the same time, at low concentrations MNPs up-taken by moDCs increased their viability causing the stimulation effect. The evaluation of the quantity of MNPs, up-taken by cells, is possible by magnetometry even for the smallest γ-Fe₂O₃ concentrations. Full article

Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode. Full article

Maghemite nanoparticles (NPs) were successfully developed using phenolic-rich extracts (cyanidin) from Citrus reticulata peel residues. The 11 nm maghemite NPs, obtained at 3% w/v and at 353 K, presented the optimal synthesis conditions. To improve dye adsorption performance, the synergetic adsorption behavior between these 11 nm NPs and multiwall carbon nanotubes was demonstrated. Prior to the adsorption tests, the aging effect on NPs was carefully assessed using various analytical techniques, which clearly showed the magnetite–maghemite phase transition. However, this had no impact on the cyanidin coating or adsorption properties. A remarkable percentage removal of (93 ± 3)% for methylene blue and (84 ± 3)% for methylene green was achieved in short equilibrium times of 10 and 25 min, respectively, with an optimum pH value of 5.5. Reuse experiments revealed that 90% removal for both dyes was achieved between the second to seventh regeneration cycles. Organic loading during these cycles was effectively confirmed by X-ray photoelectron spectroscopy and magnetic measurements. Dye adsorption involves a two-step mechanism: (i) electrostatic adsorption by the negative surface groups of the adsorbent (isoelectric point of 5.2) and the dye cationic groups and (ii) π–π stacking interactions between the aromatic benzene rings of the dyes, the hexagonal skeleton of the multiwall carbon nanotubes, and the phenolic ring groups of the biosynthesized sample. These results suggest that the low-cost modified phenolic adsorbent can be successfully applied to dye removal from water with promising recycling properties. Full article

Maghemite (γ-Fe₂O₃) nanoparticles have attracted considerable interest for electronic applications due to their tunable electrical properties. Doping strategies offer an effective way to optimize their resistive behavior for use in electronic devices. In this study, cobalt (Co) was incorporated into γ-Fe₂O₃ to enhance its resistive properties. X-ray diffraction (XRD) confirmed the retention of the cubic P4₃32 phase, with Co doping inducing subtle lattice distortions due to ionic substitution. Scanning and transmission electron microscopy (SEM/TEM) revealed morphological changes, where Co incorporation influenced particle shape and size distribution. Electrical conductivity analysis demonstrated a decrease in both AC and DC conductivity with the increase in Co content, indicating enhanced resistive behavior. The increase in activation energy suggests a reduction in charge carrier mobility, leading to higher resistivity. Impedance spectroscopy further confirmed increased real and imaginary impedance values, reinforcing the role of Co in suppressing charge transport. These results position cobalt-doped maghemite as a promising material for electronic resistive devices, such as tunable resistors and negative temperature coefficient (NTC) thermistors, where controlled conductivity and stable resistive behavior are essential. Full article

This study investigates the formation of by-product species during flame spray synthesis (SFS) of superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles. Four samples are synthesized by utilizing two standardized burner types (SpraySyn1 and SpraySyn2) and varying the iron (III) nonahydrate (INN) concentration (0.1 M and 0.2 M) in the precursor feed while using ethanol and 2-ethylhexanoic acid as solvent. Conducting complementary powder analysis revealed a predominant presence of carboxylates and carbonates as by-product species (~14–18 wt.%), while no strong indications for elemental carbon and precursor/solvent residues can be found. Carbonates/carboxylates are located on particle surfaces, and the particles’ surface loadings by these species are independent of the precursor concentration but depend on burner type, with SpraySyn2 exhibiting lower values, indicating a more complete combustion for this burner. Through time-resolved thermophoretic sampling, we further demonstrate that carbon forms temporally in the visible flame center when using SpraySyn1. Since carbon solely forms momentarily within large flame pulses and decomposes further downstream, its temporal formation is of minor relevance for the final particle purity. However, its local co-existence aside from γ-Fe₂O₃ in the flame has potential to bias in situ diagnostics. Full article

The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders in the presence of ethanol vapors as a sensitizer. This technique uses the energy from a continuous-wave CO₂ laser operating at a 9.25 μm wavelength, which is transferred to the reactive precursors via the excited ethanol molecules, inducing a rapid heating of the argon-entrained Fe(CO)₅ vapors in the presence of oxygen. For a parametric study, different samples were prepared by changing the percentages of sensitizer in the reactive mixture. Moreover, the raw samples were thermally treated at different temperatures and their morpho-structural and magnetic properties were investigated. The results indicated a high degree of crystallinity (mean ordered dimension) and enhanced magnetic properties when high percentages of ethanol vapors were employed. On the contrary, at low ethanol concentrations, due to a decrease in the reaction temperature, nanoparticles with a very low size were synthesized. The raw particles have a dimension in the range of 2.5 to 10 nm (XRD and TEM). Most of them exhibited superparamagnetic behavior at room temperature, with saturation magnetization values up to 60 emu/g. The crystalline phase detected in samples is mainly maghemite, with a decreased carbon presence (up to 8 at%). In addition to the expected Fe-OH on the particles surfaces, C (and O) bearing functional groups such as C-OH or C=O that act as a supplementary hydrophilic agent in water-based suspension were detected. Using the as-synthesized and thermally treated nanopowders, water suspensions without or with hydrophilic agents (CMCNa, L-Dopa, chitosan) were prepared by means of a horn ultrasonic homogenizer at 0.5 mg/mL concentrations. DLS analyzes revealed that some powder suspensions maintained stable agglomerates over time, with a mean size of 100 nm, pH values between 4.8 and 5.3, and zeta-potential values exceeding 40 mV. All tested agents greatly improved the stability of 250–450 °C thermally treated NPs, with L-Dopa and Chitosan inducing smaller hydrodynamic sizes. Full article

This research describes the development and thorough characterization of a novel, versatile, and biocompatible hybrid nanocarrier of the NO-releasing agent NOC-18, with a specific focus on optimizing the purification process. In this study, we focused on the sustained release of NO using biocompatible and diagnostic hybrid magnetic nanoparticles (hMNPs) containing cerium-doped maghemite (CM) NPs, embedded within human serum albumin (HSA) protein. A comprehensive study was conducted using electron paramagnetic resonance (EPR) alongside the Griess assay to evaluate NO release from the chosen NO donor, NOC-18, and to assess the limitations of the molecule under various reaction conditions, identifying the optimal conditions for binding NOC-18 with minimal NO loss. Two types of particles were designed: In-hMNPs, where NOC-18 is encapsulated within the particles, and Out-hMNPs, where NOC-18 is attached onto the surface. Our results demonstrated that In-hMNPs provided a sustained and prolonged release of NO (half-life, 50 h) compared to the rapid release for the Out-hMNPs, likely due to the strong bonds formed with cerium, which helped to stabilize the NO molecules. These results represent a promising approach to designing a dual-function agent that combines contrast properties for tumor MRI with the possibility of increasing the permeability of tumor vasculature. The employment of this dual-function agent in combination with nanotherapeutics could improve the latter’s efficacy by facilitating their access to the tumor. Full article

The evaluation of chlorhexidine-carrier nanosystems based on iron oxide magnetic nanoparticles (IOMNPs), has gained significant attention in recent years due to the unique properties of the magnetic nanoparticles (NPSs). Chlorhexidine (CHX), a well-established antimicrobial agent, has been widely used in medical applications, including oral hygiene and surgical antisepsis. This study aims to report an in vitro and in ovo toxicological screening of the synthesized CHX-NPS nanosystem, of the carrier matrix (maghemite NPSs) and of the drug to be delivered (CHX solution), by employing two types of cell lines—HaCaT immortalized human keratinocytes and JB6 Cl 41-5a murine epidermal cells. After the characterization of the CHX-NPS nanosystem through infrared spectroscopy and electronic microscopy, the in vitro results showed that the CHX antimicrobial efficacy was enhanced when delivered through a nanoscale system, with improved bioavailability and reduced toxicity when this was tested as the newly CHX-NPS nanosystem. The in ovo screening exhibited that the CHX-NPS nanosystem did not cause any sign of irritation on the chorioallantoic membrane vasculature and was classified as a non-irritant substance. Despite this, future research should focus on optimizing this type of nanosystem and conducting comprehensive in vivo studies to validate its therapeutic efficacy and safety in clinical settings. Full article

Owing to recent advancements in nanotechnology, magnetic iron oxide nanoparticles (MNPs), particularly magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃), are currently widely employed in the field of medicine. These MNPs, characterized by their large specific surface area, potential for diverse functionalization, and magnetic properties, have found application in various medical domains, including tumor imaging (MRI), radiolabelling, internal radiotherapy, hyperthermia, gene therapy, drug delivery, and theranostics. However, ensuring the non-toxicity of MNPs when employed in medical practices is paramount. Thus, ongoing research endeavors are essential to comprehensively understand and address potential toxicological implications associated with their usage. This review aims to present the latest research and findings on assessing the potential toxicity of magnetic nanoparticles. It meticulously delineates the primary mechanisms of MNP toxicity at the cellular level, encompassing oxidative stress, genotoxic effects, disruption of the cytoskeleton, cell membrane perturbation, alterations in the cell cycle, dysregulation of gene expression, inflammatory response, disturbance in ion homeostasis, and interference with cell migration and mobility. Furthermore, the review expounds upon the potential impact of MNPs on various organs and systems, including the brain and nervous system, heart and circulatory system, liver, spleen, lymph nodes, skin, urinary, and reproductive systems. Full article

Magnetic fluid hyperthermia, a minimally invasive localized therapy that uses heat generated by magnetic nanoparticles under an AC magnetic field, is a complementary approach for cancer treatment that is excellent due to its advantages of being noninvasive and addressing only the affected region. Still, its use as a stand-alone therapy is hindered by the simultaneous requirement of nanoparticle biocompatibility, good heating efficiency, and physiological safe dose. To overcome these limits, the biocompatible magnetic nanoparticles’ heating efficiency must be optimized. Iron oxide nanoparticles are accepted as the more biocompatible magnetic nanoparticles available. Therefore, in this work, superparamagnetic iron oxide nanoparticles were synthesized by a low-cost coprecipitation method and modified with starch and gum to increase their heating efficiency and compatibility with living tissues. Two different reducing agents, sodium hydroxide (NaOH) and ammonium hydroxide (NH₄OH), were used to compare their influence. The X-ray diffraction results indicate the formation of a single magnetite/maghemite phase in all cases, with the particle size distribution depending on the coating and reducing agent. Citric acid functionalized water-based ferrofluids were also prepared to study the heating efficiency of the nanoparticles under a magnetic field with a 274 kHz frequency and a 14 kAm⁻¹ amplitude. The samples prepared with NaOH display a higher specific loss power (SLP) compared to the ones prepared with NH₄OH. The SLP value of 72 Wg⁻¹ for the magnetic nanoparticles coated with a combination of starch and gum arabic, corresponding to an intrinsic loss power (ILP) of 2.60 nWg⁻¹, indicates that they are potential materials for magnetic hyperthermia therapy. Full article

In this study, we achieved the biosynthesis of novel 7–8 nm iron-oxide nanoparticles in the presence of different concentrations (5 to 50% w/v) of commercial white quinoa extract. Initially, quinoa extract was prepared at various concentrations by a purification route. The biosynthesis optimization was systematically monitored by X-ray diffraction, and the Rietveld quantitative analysis showed the presence of goethite (5 to 10 wt.%) and maghemite phases. The first phase disappeared upon increasing the organic loading (40 and 50% w/v). The organic loading was corroborated by thermogravimetric measurements, and it increased with quinoa extract concentration. Its use reduces the amount of precipitation agent at high quinoa extract concentrations with the formation of magnetic nanoparticles with hard ferrimagnetic character (42 and 11 emu g⁻¹). The enrichment of hydroxyl groups and the negative zeta potential above pH = 7 were corroborated by a reduction in the point of zero charge in all the samples. For alkaline values, the zeta potential values were above the stability range, indicating highly stable chemical species. The evidence of hydroxyl and amide functionalization was qualitatively observed using infrared analysis, which showed that the carboxyl (quercetin/kaempferol), amide I, and amide III chemical groups are retained after biosynthesis. The resultant biosynthesized samples can find applications in environmental remediation due to the affinity of the chemical agents present on the particle surfaces and easy-to-handle them magnetically. Full article