Controlling the transverse proton relaxivity of magnetic graphene oxide

The magnetic graphene oxide (MGO) composites were prepared by coprecipitation of FeCl3·6H2O and FeCl2·4H2O on graphene oxide (GO) nanosheets and characterized in detail. The Fe3O4 was uniformly deposited on the surface of GO. The synthesized MGO composites were used as a versatile adsorbent for As(V) removal from aqueous solutions. The results showed that the adsorption of As(V) on MGO is an endothermic process and the adsorption kinetic fitted the pseudo-second-order model well. The MGO composites had a good adsorption capability for As(V) removal and the adsorption isotherms were described by the Langmuir model better than by the Freundlich model. The adsorption of As(V) on MGO decreased with ascending pH due to the electrostatic interaction. In addition, the adsorption of As(V) on MGO was greatly affected by the nature and concentration of coexisting cations and anions. The presence of coexisting anions showed an inhibiting effect on As(V) adsorption, which was more efficient at low pH, whereas the presence of coexisting cations showed an enhancing effect on As(V) adsorption, which was more efficient at high pH. The results of this work indicated that the combination of the excellent adsorption capacity of GO and the magnetic properties of Fe3O4 nanoparticles is very important in drinking water treatment due to the easy magnetic separation of MGO from aqueous solutions.

Due to its remarkable properties, graphene has become a basis of many novel microelectronic devices. However its functional derivatives including graphene oxide (GO) can be mass-produced at lower costs and retain many properties of graphene in addition being water soluble. GO also exhibits fluorescence in the visible/near-IR suitable for applications in optoelectronics and biomedicine. The most novel biomedical applications of GO include, sensing, molecular imaging in visible/near-IR and drug delivery. In all these applications GO was mostly proposed as an agent for in-vitro or ex-vivo imaging due to its emission in visible or near-IR. In this work we combine GO with superparamagnetic iron oxide nanoparticles (Fe3O4 NPs) to provide the unique capacity of multimodal imaging and magnetic targeted drug delivery. Fe3O4 NPs are biocompatible and have been used as biosensing, magnetic assisted drug delivery system and also a magnetic resonance contrast agent for MRI. Additionally, these NPs can be attracted by a magnet allowing for targeting of the attached therapeutics via the magnetic field to specific organ and/or cancer tumor. In this work, we fabricate nanoconjugates of GO- Fe3O4 for combining GO fluorescence, sensing and drug delivery properties with magnetic targeting and a possibility of MRI imaging provided by Fe3O4. GO flakes were processed to have diameter mean size of 260 nm optimal for cellular internalization and conjugated to Fe3O4 NPs. For the specific application of magnetic resonance imaging, the quality of an MRI contrast agent is often evaluated by the relaxivity parameters r1 or r2, which describe the ability of a contrast agent to shorten the T1 or T2 relaxation time of water. GO-Fe3O4 showed suitable for MRI imaging relaxivity values (longitudinal r1 and transvers r2 in water at 37°C), of r1=6.6 mM-1s-1 and r2=71.1 mM-1s-1. In fact, these values are better than those for single Fe3O4 NPs: the conjugated samples showed relaxivity ratio r2/r1>2, placing them in the category of negative contrast agent. The cytotoxicity of GO-Fe3O4 established via MTT assay in HeLa cells showed over 80% viability at the imaging concentrations mimicking that of GO. Cellular uptake and imaging studies show stable internalization and localized emission inside the cells. Additionally this system provides an efficient route to pH sensing of cellular environment as spectra of in GO-Fe3O4 are highly dependent on the pH of the media. This allows to assed the presence of acidic cancerous environments for cancer therapy and detection. As a result, we propose that this new multifunctional GO-Fe3O4 composite can be used as a magnetic targeted drug delivery system, as well as biosensing and bimodal (MRI and fluorescence) imaging agent.

The sequestration of Sr(II) and Cs(I) from aqueous solutions by magnetic graphene oxides

BackgroundIn recent days, solid-phase extraction methods are widely utilized for the extraction of drug molecules from plasma samples due to their easy operating procedures and low matrix effect. The trace-level solid-phase extraction of three structurally related antiepileptic drugs brivaracetam (BVC), eslicarbazepine acetate (ESL), and carbamazepine (CBZ) was investigated by using a magnetic porous material graphene oxide-β-cyclodextrin (MGO-CD). Morphology, magnetic properties, and structure of the synthesized MGO-CD were characterized by using FT-IR, SEM, XRD, and VSM.ResultsSolid-phase extraction (SPE) methods were used to extract the analytes from human plasma. Different extraction solvents such as acetonitrile (ACN), methanol (MeOH), acetone, chloroform (CHCl3), tertiary butyl diethyl ether (TBDE), and ethyl acetate (EtOAc) with variable polarities were used to extract drug molecules from MGO-CD. The linearity analysis showed good correlation coefficient values (R2) of 0.9989, 0.9995, and 0.9982 for BVC, ESL, and CBZ respectively. The LOD and LOQ ranges were found to be 6.14–28.32 ng mL−1 and 20.45–94.31 ng mL−1 respectively.ConclusionThe high accuracy and precision made the developed HPLC method with MGO-CD a suitable alternative for the bioequivalence study of BVC, ESL, and CBZ in human plasma. This developed HPLC-UV method has good efficiency for recoveries and good linearity and is simple to handle. And also, it gave low retention time for the three antiepileptic drugs within 8 min. It provides high efficiency for the extraction of trace-level substances from human plasma.

After injury of the central and peripheral nervous systems, functional recovery is impaired by axon regeneration failure. Various approaches for promoting axon growth have been attempted but their low efficacy has prevented them from being clinically applicable. It is possible that in spite of all the research that has been performed regarding axon growth, we are still missing key aspects of axon growth biology that are essential in order to design effective treatments for axon regeneration. Most of what we know about how an axon grows has been discovered by using tools that delete, add, block, or activate macromolecules in the whole cell and by looking at its corresponding effect on axon growth. Less is known about the spatiotemporal actions of macromolecules and organelles at the growth cone and its relation with axon growth. Macromolecules and organelles are heterogeneously distributed in the cell and their resulting function depends heavily on when and where they exert their actions. We need tools that allow us to manipulate these macromolecules and organelles in a temporal window during which axon growth events are taking place. The development of such tools will provide enhanced knowledge of how an axon grows and lead to design more effective therapies to promote axon growth.

The large-scale application of ionic surfactants in industrial and agricultural production has caused great harm to the environment due to by-products. In order to remove this pollutant from the environment, graphene oxide as an adsorption material has received extensive attention. However, practically, it is difficult to separate the GO from aqueous solutions, making water treatment on a large scale challenging. To allow the recycling of GO, as well as enhance its adsorption ability to remove surfactants from water, a composite of magnetic graphene oxide (MGO) and 1-dodecyl-3-methylimidazolium chloride ionic liquid (IL) was synthesized. The MGO was prepared by coprecipitation, and IL-MGO was prepared by ultrasonic impregnation. Nitrogen adsorption-desorption curves show that the specific surface area of the composite was increased by the addition of the IL, from 103.28 to 163.35 m2/g. Finally, the adsorption ability of MGO and IL-MGO for the nonionic surfactant NP10EO was investigated. The results showed that the adsorption of MGO on NP10EO fits the Langmuir isothermal model and the quasi-second-order kinetic model. In addition, the equilibrium adsorption capacity of NP10EO by MGO at 298K, 308K, and 318K can reach 87.03 mg/g, 156.25 mg/g, and 214.13 mg/g. The adsorption is an endothermic reaction that occurs spontaneously and is governed by physical adsorption. The adsorption of IL-MGO on NP10EO conforms to the Langmuir isotherm model and the quasi-second-order kinetic model. At 298K, 308K, and 318K, the equilibrium adsorption capacity of NP10EO by MGO reached 261.02 mg/g, 280.24 mg/g, and 295.03 mg/g, respectively. Compared with the two results, the incorporation of IL greatly improved the adsorption capacity of MGO to NP10EO.

This study aims at the functionalization of magnetic graphene oxide nanosheets and the binding of humic acid as a lead complex ligand. Graphene oxide nanosheets possess a large surface area and various carboxylic acid groups which can be activated easily by activating agents. Therefore, they are suitable to be used for the extraction of heavy metals. To have a better process of extracting lead ions, magnetic graphene oxide was used in this research. Humic acid, as a lead metal complex agent, has an amine functional group which can be bound to modified graphene oxide from one side. The process of constructing the nano-adsorbent proposed for the preconcentration of lead ions as well as its characterization was studied by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The designed nano-adsorbent was tested to measure lead ions in simulated and real samples of sea water, fish, and oysters. The detection limit obtained in the simulated samples was 0.07μg/L, and the linear range was 0.2-12μg/L. The apparatus used to measure the ions was a flame atomic absorption device. In the analysis of the real samples, the values obtained through flame atomic absorption were compared with those obtained through furnace atomic absorption. The proposed technique is advantageous due to being cheap, precise, and sensitive for the trace measurement of lead ions.

Graphene oxide (GO) is a nanomaterial with excellent physico‐chemical properties widely used in a high variety of technological applications. However, conventional protocols for GO preparation rely on wet synthesis, involving extreme chemical conditions. Recently, mechanochemical synthesis has been postulated as a rapid and sustainable dry alternative for the preparation of new materials. In this work, an optimization of the mechanochemical synthesis of GO from graphite is carried out. To characterize the materials, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐Ray photoelectron microscopy (XPS), elemental analysis, and nitrogen adsorption–desorption isotherms are employed. The GO synthesized via dry protocol (d‐GO) and GO prepared via wet synthesis (w‐GO) are coupled with magnetic nanoparticles (MNPs) to prepare magnetic graphene oxide sorbents (d‐M@GO and w‐M@GO). Subsequently, the adsorption properties of the prepared materials toward inorganic and organic pollutants are determined and compared. The results indicated excellent adsorption efficiency for d‐M@GO, demonstrating the successful application of the mechanochemical method in magnetic sorbents preparation. To the best of the available knowledge, this is the first work to investigate the applicability of dry mechanochemical GO for the synthesis of a magnetic sorbent (d‐M@GO) and its use toward emerging concern and priority pollutants (PFAS and metal ions).

Highly efficient recovery of heavy rare earth elements by using an amino-functionalized magnetic graphene oxide with acid and base resistance

Trace concentrations of graphene oxide and magnetic graphene oxide rescue anaerobic municipal sludge digesters under stress

Hematoporphyrin-conjugated magnetic graphene oxide nanocomposite was designed and prepared as a novel promising model. Fe3O4 nanoparticles were dispersed on the surface and edges of the graphene oxide in a uniform size, and hematoporphyrin was effectively conjugated onto graphene oxide via hydrophobic interactions and π-π stacking. With the photosensitivity of hematoporphyrin and the magnetic properties of Fe3O4 nanoparticles, it can be applied for photodynamic therapy to increase the accumulation of hematoporphyrin in tumor cells. The cytotoxicity in vitro showed that hematoporphyrin conjugated magnetic graphene oxide nanocomposite irradiated at 671 nm generated cytotoxic singlet oxygen and exhibited a good inhibition to the human tumor cell HeLa (IC50 = 10.12 µg/ml), which suggested that the nanocomposite is potential for targeting photodynamic therapy as a promising drug delivery system.

Utilizing office waste paper for environmental treatments has garnered significant interest from the research community, as it addresses both waste management and the development of low-cost sustainable adsorbents. In this study, a novel approach was developed by integrating office waste paper-derived fibrillated cellulose (PFC) with magnetic graphene oxide (M-GO) to develop a composite adsorbent for the removal of tetracycline (TC) from aqueous solutions. PFC was isolated via an alkali-acid treatment process; graphene oxide (GO) was synthesized using a modified Hummers' method and subsequently functionalized with magnetite nanoparticles to produce M-GO. The M-GO/PFC composite was then prepared using an ultrasound-assisted mixing technique, followed by lyophilization. Materials were characterized using Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, N2 adsorption–desorption isotherms, and vibrating sample magnetometry (VSM). The effects of solution pH, adsorbent dose, and ionic strength on TC removal by the composite adsorbent were systematically investigated. Adsorption kinetics was analyzed using the pseudo-first-order, pseudo-second-order, and Elovich models, suggested to fit well with the pseudo-second-order kinetic model with an initial rate of 18.09 mg g−1 min−1. Adsorption isotherms were evaluated using the Langmuir, Freundlich, Sips, and Temkin models, of which the Sips model best described the experimental data, yielding a maximum adsorption capacity of 130.11 mg g−1. Recyclability testing was carried out through five successive adsorption–desorption cycles, indicating a stable adsorption performance of the composite adsorbent with 12.9% decrease between the first and the fifth cycle. These findings suggest that the M-GO/PFC composite is a promising and effective adsorbent for the removal of TC and potentially other water-soluble antibiotics from aqueous environments.

Aedes-borne diseases are of worldwide concern due to the lack of effective medicine and vaccination. Frequent use of chemical intervention has developed insecticide resistance in mosquitoes and posed health risks to humans and the environment, necessitating an effective and safer intervention. Graphene Oxide (GO) is an efficient material that can absorb pesticide particles and release pesticide macromolecules in a controlled manner. With the proposition that magnetic graphene oxide (MGO)-based nanoformulations can be an eco-safe and effective material for pesticide conjugation, the present study synthesized these nanoformulations conjugated with a pyrethroid, deltamethrin (DL) through chemical co-precipitation method. The formulations were validated using biophysical techniques and investigated for their efficacy against Aedes aegypti. The X-ray diffraction (XRD) pattern of nanocomposites showed six intense diffraction peaks of Fe3O4 particles, X-ray photoelectron spectroscopy (XPS) displayed the C1s, O1s, and Fe2p photoelectron lines in the MGO nanocomposite's spectra, while Field Emission Scanning Electron Microscopy (FESEM) revealed the small size and uniformity of Fe3O4 nanoparticles on the GO surface. The individual MGO and DL, as well as MGO-DL binary combinations (1:1, 1:2, and 1:3) imparted significant larval toxicity, demonstrating 30%, 50%, and 85% CTC (Co-toxicity coefficient), respectively. High corresponding Synergistic factor (SF) values indicated significant synergism increasing with the rise in deltamethrin proportion. The MGO-DL combinations also increased irritancy and flight response in adults, the notable synergistic effects imparted by the 1:3 combination. The effective actions of MGO-DL nanoformulations against mosquitoes suggest their possible use for mosquito management as a safer and more operative intervention.

From signal amplification to restrained background: Magnetic graphene oxide assisted homogeneous electrochemiluminescence aptasensor for highly sensitive detection of okadaic acid

Nanoparticles have been widely applied to treat emulsion-containing wastewater in the form of chemical demulsifiers, such as SiO2, Fe3O4, and graphene oxide (GO). Owing to their asymmetric structures and selective adsorption, Janus nanoparticles show greater application potential in many fields. In the present work, the novel magnetic Janus graphene oxide (MJGO) nanoparticle was successfully prepared by grafting magnetic Fe3O4 to the surface of the JGO, and its demulsifying ability to treat a crude oil-in-water emulsion was evaluated. The MJGO structure and its magnetic intensity were verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and magnetization saturation (MS) tests. Compared with GO and JGO, MJGO displayed the superior efficiency (>96%) to demulsify the crude oil-in-water emulsion, which can be attributed to the reduced electrostatic repulsion between MJGO and the emulsion droplets. Furthermore, the effects of pH and temperature on the demulsification performance of MJGO were also studied. Lastly, the recyclability of MJGO largely reduced the cost of demulsifiers in separating crude oil and water. The current research presents an efficient and recyclable demulsifier, which provides a new perspective for the structural design of nanomaterials and their application in the field of demulsification.