Superparamagnetic Fe3O4 Research Articles

Design and controlled synthesis of molecularly imprinted fluorescence sensor supported by multifunctional magnetic covalent organic framework: Efficient detection of clofibric acid in the environment

While some studies have explored magnetic covalent organic frameworks (MCOFs) for fluorescence sensing, substantial research gaps remain, especially in integrating molecular imprinting technology (MIT). In this study, superparamagnetic Fe3O4 cores were modified, and a monomer-mediated in situ growth strategy was used to synthesize uniform, multifunctional MCOFs nanoparticles. Subsequently, molecularly imprinted polymers (MIPs) were synthesized via a sol-gel method and deposited on MCOFs, forming MCOFs-supported molecularly imprinted fluorescent sensors (MCOFs@MIPs) for trace analysis of clofibric acid (CLF). This was the first application of molecularly imprinted fluorescence sensing technology for detecting CLF. MCOFs@MIPs combined the superparamagnetism of Fe3O4, the stability and signal amplification of COFs, and the selectivity of MIPs for CLF. Studies demonstrated that MCOFs@MIPs had a maximum fluorescence response in isopropanol, with an optimal dosage of 0.39 mg/mL, an imprinting factor (IF) of 2.73, a detection limit of 94 nM, and a range of 0 ∼ 300 µM. Characterizations revealed that the fluorescence quenching of MCOFs@MIPs was based on a photoinduced electron transfer (PET) mechanism, with MCOFs@MIPs as donors and CLF as acceptors. MCOFs@MIPs were used to detect CLF in actual samples from food, water, agricultural products, cosmetics, and human metabolites. The detection results were consistent with those from high-performance liquid chromatography (HPLC). Additionally, the recoveries of MCOFs@MIPs for actual samples ranged from 94.4 % to 100.7 %, demonstrating exceptional reliability, reusability, and accuracy.

Enhanced functionalization of superparamagnetic Fe3O4 nanoparticles for advanced drug enrichment and separation applications

Backgroundsuperparamagnetic ferroferric oxide (Fe3O4) nanoparticles can be extensively functionalized for applications in drug enrichment and separation. Their high magnetic responsiveness and controllable surface modification enable rapid drug enrichment and separation under external magnetic fields. This study aimed to enhance the application potential of superparamagnetic Fe3O4 nanoparticles in the field of drug enrichment and separation by functionalizing these nanoparticles to improve their biocompatibility and targeting capabilities.Methodssuperparamagnetic Fe3O4 nanoparticles functionalized with dopamine were synthesized using benzyl alcohol as the solvent and iron acetylacetonate as the precursor. The dopamine-functionalized superparamagnetic iron oxide nanoparticles were used to analyze protein enrichment and separation. Characterization of the nanoparticles was conducted, including analysis of particle size distribution, Zeta potential, and fluorescence spectra using a fluorescence spectrophotometer.Resultsthe Fe3O4 nanoparticles maintained high magnetism from the original material and exhibited uniform particle size distribution and stable Zeta potential. The saturation magnetization of dopamine-functionalized superparamagnetic Fe3O4 nanoparticles showed no significant difference compared to before coating, indicating minimal influence of dopamine on the internal magnetic core of the nanoparticles. The Fe3O4 nanoparticles demonstrated good biocompatibility and stability.Conclusionfunctionalization of superparamagnetic Fe3O4 nanoparticles significantly enhances their efficiency in drug enrichment and separation processes, suggesting broad applications in the pharmaceutical industry.

A DNA machine-based magnetic resonance imaging nanoprobe for in vivo microRNA detection

In situ monitoring microRNA (miRNA) expression in vivo holds immense potential for directly visualizing the occurrence and progression of tumors. However, the significant barrier to developing a probe that can overcome the low abundance of miRNAs while providing an output signal with unlimited tissue penetration depth remains formidable. In this study, we developed a DNA machine-based magnetic resonance imaging nanoprobe (MRINP) for amplified detection of miR-21 in vivo. The MRINP was constructed with superparamagnetic Fe3O4 nanoparticles (NPs), paramagnetic Gd-DOTA complexes, and miR-21-activated DNA machines; the DNA machine was composed of hairpin DNAzyme (HD) strands serving as the DNAzyme walker and hairpin substrate (HS) strands serving as the track. Once uptake into tumor cells, the intracellular miR-21 specifically recognized and hybridized with the HD strand, restoring the activity of DNAzyme. Subsequently, the DNAzyme walker autonomously traveled on the surface of MRINP, and each step movement of the DNAzyme walker resulted in the cleavage of its substrate strands and the ensued release of the Gd-DOTA complex-labeled oligonucleotides, turning on the T1 signal of Gd-DOTA complexes for in situ imaging of miR-21 in tumor-bearing mice. This strategy would offer a promising approach for mapping tumor-specific biomarkers in vivo with unlimited penetration depth.

Synthesis of superparamagnetic Fe3O4–graphene oxide-based material for the photodegradation of clonazepam

The global concern over water pollution caused by contaminants of emerging concern has been the subject of several studies due to the complexity of treatment. Here, the synthesis of a graphene oxide-based magnetic material (GO@Fe3O4) produced according to a modified Hummers’ method followed by a hydrothermal reaction was proposed; then, its application as a photocatalyst in clonazepam photo-Fenton degradation was investigated. Several characterization analyses were performed to analyze the structure, functionalization and magnetic properties of the composite. A 23 factorial design was used for the optimization procedure to investigate the effect of [H2O2], GO@Fe3O4 dose and pH on clonazepam degradation. Adsorption experiments demonstrated that GO@Fe3O4 could not adsorb clonazepam. Photo-Fenton kinetics showed that total degradation of clonazepam was achieved within 5 min, and the experimental data were better fitted to the PFO model. A comparative study of clonazepam degradation by different processes highlighted that the heterogeneous photo-Fenton process was more efficient than homogeneous processes. The radical scavenging test showed that O2·-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${O}_{2}^{\\cdot -}$$\\end{document} was the main active free radical in the degradation reaction, followed by hydroxyl radicals (•OH) and holes (h+) in the valence layer; accordingly, a mechanism of degradation was proposed to describe the process.

Superparamagnetic Fe3O4 nanoparticles capped with silver induce apoptosis of colon cancer cells via damaging DNA@increasing ROS

A sol-gel approach was used to create magnetite nanoparticles (Fe3O4 NPs) as a core and silver (Ag) as a shell. Ag-Fe3O4 NPs were identified by x-ray diffraction (XRD) and energy dispersive x-ray (EDX), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, and vibrating sample magnetometer (VSM) techniques. The capabilities of Ag-Fe3O4 NPs to induce apoptosis were investigated utilizing the Acridine orange/Ethidium bromide stain. The activity of NPs against (HT-29) cancer cells was further evaluated in and out of the existence of near-infrared (NIR) laser beam and alternating magnetic field (AMF). The exposed laser enhanced the cytotoxicity effect against (HT-29) cells. However, greatly elevated cytotoxic activity was seen with using the AMF.

Green Synthesis of Pure Superparamagnetic Fe3O4 Nanoparticles Using Shewanella sp. in a Non-Growth Medium

Conventional wet chemical methods for the synthesis of superparamagnetic magnetite nanoparticles (MNPs) are energy-intensive and environmentally unsustainable. Green synthesis using bacteria is a less-explored approach to MNP production. Large-scale biosynthesis of MNPs has heretofore been conducted using extremophilic bacteria that exhibit low growth rates and/or require strict temperature control. However, a decrease in material and energy costs would make such bioprocesses more sustainable. In this study, Shewanella putrefaciens CN-32, an iron-reducing bacterium, was employed to reduce amorphous iron oxyhydroxide and synthesize MNPs in a non-growth medium at ambient temperature and pressure. The synthesis was conducted using plain saline solution (0.85% NaCl) to avoid impurities in the products. X-ray diffraction and transmission electron microscopy indicated that the reduction products were MNPs with a pseudo-spherical shape and 6 ± 2 nm average size. Magnetometry showed that the particles were superparamagnetic with maximum saturation magnetization of 73.8 emu/g, which is comparable to that obtained via chemical synthesis methods. Using less than a quarter of the raw materials employed in a typical chemical co-precipitation method, we obtained a maximum yield of 3.473 g/L (>5-fold increase). These findings demonstrate that our simple and ecofriendly process can help overcome the current barriers for large-scale synthesis of high-purity magnetic nanopowders.

The immobilization of L-Valine on superparamagnetic Fe3O4 nanoparticles as a novel, recoverable and green nanocatalyst for the synthesis of new thiazole derivatives

The novel immobilization of L-Valine on superparamagnetic Fe3O4 nanoparticles was prepared using a simple protocol for the first time. This compound acts as a highly efficient and recyclable heterogeneous nanocatalyst for the synthesis of thiazole derivatives via a one-pot and multi-component condensation reaction of arylglyoxals monohydrate, cyclic 1,3-dicarbonyls, and thiobenzamides in a water solvent. The structure of the nanocatalyst was characterized and confirmed using various techniques, such as Fourier transform infrared spectroscopy (FT-IR), Energy Dispersive X-ray (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG/DTA), and vibrating sample magnetometry (VSM). This heterogeneous nanocatalyst can be easily recovered from the reaction mixture by an external magnetic field and reused for subsequent reactions at least five times without losing significant catalytic activity.

Purification, Characterization, and Assessment of Anticancer Activity of Iron Oxide Nanoparticles Biosynthesized by Novel Thermophilic Bacillus tequilensis ASFS1‏.

Magnetic nanoparticles (MNPs), particularly iron oxide nanoparticles (IONPs), are a fascinating group of nanoparticles that have been considerably investigated for biomedical applications because of their superparamagnetic properties, biodegradable nature, and biocompatibility. A novel Gram-positive moderately thermophilic bacterial strain, namely Bacillus tequilensis ASFS.1, was isolated and identified. This strain is capable of producing superparamagnetic Fe3O4 nanoparticles and exhibiting magnetotaxis behavior. This strain swimming behavior was investigated under static and dynamic environments, where it behaved very much similar to the magnetotaxis in magnetotactic bacteria. This study is the first report of a bacterium from the Bacillaceae family that has the potential to intracellular biosynthesis of IONPs. MNPs were separated by a magnetic and reproducible method which was designed for the first time for this study. In addition, UV-visible spectrophotometer, Fourier-transform infrared spectroscopy, vibrating sample magnetometer, field emission scanning electron microscopy (FESEM), X-ray diffraction, and thermal gravimetric analysis were utilized to characterize the bio-fabricated magnetite nanoparticles. Analysis of the particle size distribution pattern of the biogenic MNPs by FESEM imaging revealed the size range of 10-100 nm with the size range of 10-40 nm MNPs being the most frequent particles. VSM analysis demonstrated that biogenic MNPs displayed superparamagnetic properties with a high saturation magnetization value of 184 emu/g. After 24 h treatment of 3T3, U87, A549, MCF-7, and HT-29 cell lines with the biogenic MNPs, IC50 values were measured to be 339, 641, 582, 149, and 184 μg mL-1, respectively. This study presents the novel strain ASFS.1 capable of magnetotaxis by the aid of its magnetite nanoparticles and paving information on isolation, characterization, and in vitro cytotoxicity of its MNPs. The MNPs showed promising potential for biomedical applications, obviously subject to additional studies.

The synthesis of Fe3O4@SiO2 superparamagnetic materials and mechanism of catalysis

Abstract The superparamagnetic Fe3O4 was fabricated by the solvothermal synthesis, in which medium ferric chloride is the iron source and deoxidizer using as ethylene glycol. The core-shell material Fe3O4@SiO2 was fabricated by the scheme which was composed of Anhydrous ethanol, deionized water, ammonia water, and tetraethyl orthosilicate (TEOS). The structural and optical characteristics of the samples Fe3O4 and core-shell Fe3O4@SiO2 was detected by X-ray diffraction (XRD), transmission electron microscope (TEM), Vibrating sample magnetometer (VSM), and UV/VIS/IR spectrophotometer. The conclusions illustrate that the spherical core-shell structure of Fe3O4 and Fe3O4@SiO2 were fabricated with superparamagnetic. The Ostwald ripening effect on structure of sample Fe3O4 was concluded to form inverse spinel polycrystal structure by nanometer particles. The visual-driven photocatalytic properties of Fe3O4 and Fe3O4@SiO2 nanoparticles toward the deposition of methodology blue was studied. The obtained conclusions indicate that Fe3O4@SiO2 after irradiated by visible light, its degradation rate of methodology methylene mlue (MB) was enhanced than Fe3O4 in the presence of H2O2. The samples Fe3O4 and core-shell Fe3O4@SiO2 materials are recycled by external magnetic field and reused for special superparamagnetic property. The sample Fe3O4 and core-shell Fe3O4@SiO2 materials represent higher catalytic property and excellent fixity consistent with the decomposition rate of methodology methylene mlue (MB) after being recycling and reuse severe times. The photocatalytic mechanism was dismissed based on the determined active agent during the process of degraded wastewater.

Preparation and Characterization of C@Fe3O4 Supported Pd Magnetic Nanoparticles for Degradation of Dye Wastewater

The core-shell structure Fe3O4@C magnetic nanoparticles were synthesized with superparamagnetic Fe3O4 nanosphere as a magnetic core, and soluble starch resin as a carbon source via a solvothermal method. Silica-iron oxide and Fe3O4@C carriers with a core-shell structure were prepared by carbonization of organic material on the surface of Fe3O4 nanoparticles, Fe3O4@C supported Pd were processed into magnetic nano-catalysts with core-shell structure, and their catalytic properties were investigated. The resulting environmentally friendly magnetic material can be used to degrade dye wastewater. The structure of magnetic nanoparticles was characterized using TEM, XRD and VSM. The effects of preparation conditions in the structure of the Fe3O4@C magnetic nanoparticles were taken out. The results indicate that from XRD, the magnetic nano particles Fe3O4@C synthesized of carbon sources have amorphous carbon diffraction peak except for all the characteristic peaks of Fe3O4. The saturation magnetization Fe3O4, Fe3O4@SiO2 and Fe3O4@C – 59.14 emu/g, 49.12 emu/g and 27.95 emu/g, respectively.

Synthesis of Controllable Superparamagnetic Nano Fe3O4 Based on Reduction Method for Colloidal Clusters of Magnetically Responsive Photonic Crystals.

In this paper, we designed and investigated a reduction-based method to synthesize controllably monodisperse superparamagnetic nano Fe3O4 colloidal clusters for magnetically responsive photonic crystals. It was shown that the addition of ascorbic acid (VC) to the system could synthesize monodisperse superparamagnetic nano Fe3O4 and avoided the generation of γ-Fe2O3 impurities, while the particle size and saturation magnetization intensity of nano Fe3O4 gradually decreased with the increase of VC dosage. Nano Fe3O4 could be rapidly assembled into photonic crystal dot matrix structures under a magnetic field, demonstrating tunability to various diffraction wavelengths. The nano Fe3O4 modified by polyvinylpyrrolidone (PVP) and silicon coated could be stably dispersed in a variety of organic solvents and thus diffracted different wavelengths under a magnetic field. This is expected to be applied in various scenarios in the field of optical color development.

Minimally Invasive Delivery of Percutaneous Ablation Agent via Magnetic Colloidal Hydrogel Injection for Treatment of Hepatocellular Carcinoma.

Percutaneous thermotherapy, a minimally invasive operational procedure, is employed in the ablation of deep tumor lesions by means of target-delivering heat. Conventional thermal ablation methods, such as radiofrequency or microwave ablation, to a certain extent, are subjected to extended ablation time as well as biosafety risks of unwanted overheating. Given its effectiveness and safety, percutaneous thermotherapy gains a fresh perspective, thanks to magnetic hyperthermia. In this respect, an injectable- and magnetic-hydrogel-construct-based thermal ablation agent is likely to be a candidate for the aforementioned clinical translation. Adopting a simple and environment-friendly strategy, a magnetic colloidal hydrogel injection is introduced by a binary system comprising super-paramagnetic Fe3O4 nanoparticles and gelatin nanoparticles. The colloidal hydrogel constructs, unlike conventional bulk hydrogel, can be easily extruded through a percutaneous needle and then self-heal in a reversible manner owing to the unique electrostatic cross-linking. The introduction of magnetic building blocks is exhibited with a rapid magnetothermal response to an alternating magnetic field. Such hydrogel injection is capable of generating heat without limitation of deep penetration. The materials achieve outstanding therapeutic results in mouse and rabbit models. These findings constitute a new class of locoregional interventional thermal therapies with minimal collateral damages.

Induction heating of magnetic nanoparticles: role of thermo-physical properties of the coating moieties

Superparamagnetic nanoparticles (MNPs) are utilized for magnetic fluid hyperthermia (MFH)-based cancer therapeutics, where the MNPs are surface functionalized to impart desired stability and biological properties. In this study, the MFH properties of palmitic (PA) and stearic (SA) acid-coated superparamagnetic Fe3O4 MNPs, with similar sizes (∼ 10 ± 0.8 nm, and ∼ 11 ± 0.7 nm, respectively), and saturation magnetizations (∼ 40.8 emu/g, and ∼ 41 emu/g, respectively), are systematically probed to understand the role of the thermo-physical properties of the coating moieties on the MFH efficiency. PA and SA-coated MNPs are prepared using a one-step microwave-assisted co-precipitation technique, and the presence of the surface coatings is confirmed using Fourier transform infrared spectroscopy and thermogravimetric analyses. Magneto-calorimetric studies show a high induction heating efficiency, surpassing the threshold of MFH for a biologically relevant field-frequency range. The maximum heating efficiencies are found to be ∼ 164.5 ± 5.4 W/gFe and ∼ 223.9 ± 6.4 W/gFe for the PA and SA-coated MNPs, respectively. This indicates ∼ 36.1 % higher specific absorption rate (SAR) for the SA-coated MNPs under similar experimental conditions, even though the magneto-structural properties are identical for the PA and SA-coated MNPs. Further, finite element modelling is utilized to investigate the thermal transport from the magnetic core to the surrounding medium, where the thermo-physical properties of the coating moieties are considered. Finite element simulations indicate ∼ 32.6 % higher SAR for the SA-coated MNPs, which is consistent with the experimental findings. The higher SAR for the SA-coated MNPs is attributed to the ∼ 1.7 times higher thermal diffusivity of SA. The proposed model is experimentally validated using a third system consisting of lauric acid-coated Fe3O4 MNPs with comparable magneto-structural properties. Further, significant temperature rise in a tissue-equivalent agar medium and good bio-compatibility, as indicated by the in vitro cyto-toxicity studies, make the prepared MNPs potential candidates for MFH applications. The obtained results provide deeper insight into the role of the thermo-physical properties of the coating moieties on the induction heating efficiency of superparamagnetic MNPs.

Magnetic lanthanide sensor with self-ratiometric time-resolved luminescence for accurate detection of epithelial cancerous exosomes.

Fluorescence-based LB (liquid biopsy) offers a rapid means of detecting cancer non-invasively. However, the widespread issue of sample loss during purification steps will diminish the accuracy of detection results. Therefore, in this study, we introduce a magnetic lanthanide sensor (MLS) designed for sensitive detection of the characteristic protein, epithelial cell adhesion molecule (EpCAM), on epithelial tumor exosomes. By leveraging the inherent multi-peak emission and time-resolved properties of the sole-component lanthanide element, combined with the self-ratiometric strategy, MLS can overcome limitations imposed by manual operation and/or sample complexity, thereby providing more stable and reliable output results. Specifically, terbium-doped NaYF4 nanoparticles (NaYF4:Tb) and deformable aptamers terminated with BHQ1 were sequentially introduced onto superparamagnetic silica-decorated Fe3O4 nanoparticles. Prior to target binding, emission from NaYF4:Tb at 543 nm was partially quenched due to the fluorescence resonance energy transfer (FRET) from NaYF4:Tb to BHQ1. Upon target binding, changes in the secondary structure of aptamers led to the fluorescence intensity increasing since the deconfinement of distance-dependent FRET effect. The characteristic emission of NaYF4:Tb at 543 nm was then utilized as the detection signal (I1), while the less changed emission at 583 nm served as the reference signal (I2), further reporting the self-ratiometric values of I1 and I2 (I1/I2) to illustrate the epithelial cancerous features of exosomes while ignoring possible sample loss. Consequently, over a wide range of exosome concentrations (2.28 × 102-2.28 × 108 particles per mL), the I1/I2 ratio exhibited a linear increase with exosome concentration [Y(I1/I2) = 0.166 lg (Nexosomes) + 3.0269, R2 = 0.9915], achieving a theoretical detection limit as low as 24 particles per mL. Additionally, MLS effectively distinguished epithelial cancer samples from healthy samples, showcasing significant potential for clinical diagnosis.

Precise air oxidation for continuous production of superparamagnetic Fe3O4 nanoparticles at room temperature through a microfilm reactor.

Superparamagnetic iron oxide nanoparticles (SPIONs) find vast applications in biomedicine such as drug delivery, magnetic resonance imaging (MRI) contrast agents, cell separation, tissue repair, etc. The synthesis of pure and uniform SPIONs involves tedious processes, complex precursors, the assistance of organic solvents, capping agents and/or high temperature. Herein, we report a continuous mass production of pure and uniform SPIONs in aqueous microfilm at room temperature without using any surfactant. The air oxidation rate and nanocrystal formation kinetics were precisely controlled by process intensification in the continuously flowing microfilm. Precise oxidation of Fe(ii) is a synergy of disc spinning speed and feeding concentration. The production process was continuous and conducted at room temperature in an aqueous medium with a high yield of 55.4 g h-1. The obtained products were proved to be highly pure through XRD and a colorimetric method. The resulting SPIONs exhibited a narrow size distribution, ranging from 6.5 to 12.6 nm. All sizes of the produced nanoparticles showed characteristic superparamagnetism, with the 12.6 nm SPIONs exhibiting the highest magnetization saturation (M s) of 87 emu g-1.

Superparamagnetic Artificial Cells PLGA-Fe3O4 Micro/Nanocapsules for Cancer Targeted Delivery.

Artificial cells have been extensively used in many fields, such as nanomedicine, biotherapy, blood substitutes, drug delivery, enzyme/gene therapy, cancer therapy, and the COVID-19 vaccine. The unique properties of superparamagnetic Fe3O4 nanoparticles have contributed to increased interest in using superparamagnetic artificial cells (PLGA-Fe3O4 micro/nanocapsules) for targeted therapy. In this review, the preparation methods of Fe3O4 NPs and superparamagnetic artificial cell PLGA-drug-Fe3O4 micro/nanocapsules are discussed. This review also focuses on the recent progress of superparamagnetic PLGA-drug-Fe3O4 micro/nanocapsules as targeted therapeutics. We shall concentrate on the use of superparamagnetic artificial cells in the form of PLGA-drug-Fe3O4 nanocapsules for magnetic hyperthermia/photothermal therapy and cancer therapies, including lung breast cancer and glioblastoma.

The Effect of Superparamagnetic Fe3O4 Nanoparticles Combined with Quercetin on Breast Cancer Cell Line (MCF-7)

Background: Magnetic nanoparticles attract increasing interest due to their use in cancer therapy and as drug carriers for several other diseases. The present study investigates the physiochemical properties of quercetin-conjugated superparamagnetic Fe3O4 nanoparticles and their effects on breast cancer cell line MCF-7. Methods: A simple precipitation method was used to prepare the Poly Ethylene Imine (PEI)-coated Fe3O4 nanoparticles; they were then conjugated with flavonoid-compound quercetin on the surface via carboxylic/amine group using nanoprecipitation method. Then, the physical and chemical parameters were calculated using Zeta-sizer, scanning electron microscopy (SEM), and extract release patterns at 37 and 42 0C. Finally, the toxicity level of this quercetin- conjugated nanosystem on the MCF-7 cells was investigated by MTT assay. Results: The results showed that the prepared nanosystem attained about 74% of quercetin inclusion, 91.2 nm size, 65.1 mV zeta potential, spherical morphology and a controlled release. Compared to Fe3O4 nanoparticles and pure quercetin, MTT and microscopy analysis revealed that quercetin-conjugated Fe3O4 nanoparticles induced considerable cytotoxicity, and morphology changes against MCF7 cells. Conclusion: Quercetin-conjugated Fe3O4 nanoparticles have appropriate physiochemical properties; they can be a suitable carrier for drug delivery and a promising therapy for candidates.

Tailored synthesis of iron oxide nanoparticles for specific applications using a statistical experimental design

For this work, iron oxide nanoparticles are synthesized by the co-precipitation method with stoichiometric amounts of Fe2+ and Fe3+ salts in a 1:2 ratio in distilled water and the pH is raised by adding an aqueous ammonia solution by controlled dripping. Nanoparticles precipitating after the reaction time are magnetically filtered and stored in ethanol for further analysis. Superparamagnetic Fe3O4 nanoparticles with a slight deviation from the stoichiometry are obtained, with sizes between 7.4 and 12.8 nm and saturation magnetization between 40 and 78 emu/gr. At pH 6, rod-shaped nanoparticles are obtained in addition to spherical ones. With a statistical design, it is shown how the morphological, structural and magnetic properties of the resulting nanoparticles can be manipulated by the synthesis parameters, offering many possibilities to tailor the materials to a wide range of applications.

An LF-NMR homogeneous immunoassay for Vibrio parahaemolyticus based on superparamagnetic 2D nanomaterials

In this work, a sensitive low field nuclear magnetic resonance (LF-NMR) homogeneous immunoassay, also called magnetic resonance switch (MRSw) sensor, for Vibrio parahaemolyticus (VP) was developed. Superparamagnetic 2D nanomaterial was designed and used as the magnetic probe of MRSw sensor. It was GO@SPIONs&Ab, a composite nanomaterial with many superparamagnetic Fe3O4 nanoparticles (SPIONs) providing a magnetic signal and VP antibody (Ab) specifically recognizing the target VP evenly distributed on the surface of GO. The presence of VP controllably changed the aggregation state of the probe, eliminating the uncertainty of MRSw sensor type, and thus then achieving a regular variation of transverse relaxation time T2 and ensuing quantitative detection of VP. Triple signal enhancement of the MRSw sensor was obtained due to the application of the designed 2D probe, by increasing the number of SPIONs, improving the magnetic intensity and susceptibility, and forming a synergistic effect. Under optimized experimental conditions, VP could be detected with satisfied sensitivity, selectivity, precision, accuracy, and stability, even in turbid real samples. LOQ for VP was 10 CFU/mL. This detection principle is widely applicable, providing an idea for the construction of highly sensitive MRSw sensors.

Synthesis of Fluorous Ferrofluids and Effects of the Nanoparticle Coatings on Field- and Temperature-Dependent Magnetizations.

Ferrofluids have been extensively employed in industrial, environmental, and biomedical areas. Among them, fluorous ferrofluids are of particular interest because of the biorthogonal nature of perfluorocarbons (PFCs). However, the noninteracting nature of PFCs as well as challenges in functionalization of nanoparticle surfaces with fluorous ligands has limited their applications, especially in biomedicine. In particular, commercially available fluorous ferrofluids are stabilized using ionic surfactants with charged groups that physically interact with a wide range of charged biological molecules. In this paper, we developed a unique two-phase ligand attachment strategy to render stable fluorous ferrofluids using nonionic surfactants. The superparamagnetic Fe3O4 or MnFe2O4 core of the magnetic nanoparticles, the magnetic component of the ferrofluid, was coated with a silica shell containing abundant surface hydroxyl groups, thereby enabling the installation of fluorous ligands through stable covalent, neutral, siloxane bonds. We explored chemistry-material relationships between different ligands and PFC solvents and found that low-molecular-weight ligands can assist with the installation of high-molecular-weight ligands (4000-8000 g/mol), allowing us to systematically control the size and thickness of ligand functionalization on the nanoparticle surface. By zero-field-cooled magnetization measurements, we studied how the ligands affect magnetic dipole orientation forces and observed a curve flattening that is only associated with the ferrofluids. This work provided insight into ferrofluids' dependence on interparticle interactions and contributed a methodology to synthesize fluorous ferrofluids with nonionic surfactants that exhibit both magnetic and chemical stability. We believe that the doped MnFe2O4 fluorous ferrofluid has the highest combination of stability and magnetization reported to date.