Adsorption of microcystin-Lr onto iron oxide nanoparticles

In this study, the adsorption of microcystin-LR onto iron oxide (maghemite) nanoparticles from water was examined. Factors influencing the sorption behavior included microcystin and maghemite concentration, pH, ionic strength, and the presence of natural organic matter. Adsorption of microcystin-LR was strongly affected by pH. The adsorption increased with decreasing pH, with a maximum adsorption around pH 3. Adsorption of microcystin-LR on maghemite was primarily attributed to electrostatic interactions, although hydrophobic interactions may also play a role. The extent of microcystin-LR adsorption onto maghemite increased with increasing ionic strength at pH 6.4, since salt ions screened the electrostatic repulsion between adsorbed microcystin molecules. Adsorption of microcystin-LR was not significantly affected by the presence of Suwannee River Fulvic acid (SRFA) below 2.5 mg/L. However, adsorption decreased at higher SRFA concentrations (2.5–25 mg/L) due to competitive adsorption between SRFA and microcystin-LR for limited sorption sites.     

Morphology- and phase-controlled iron oxide nanoparticles stabilized with maleic anhydride grafted polypropylene

About phase: Ferromagnetic γ-Fe(2) O(3) nanowires (left in the figure) with a saturation magnetization (M(s) ) of 54.0?emu?g(-1) and coercivity of 518?Oe at room temperature, and superparamagnetic hollow α-Fe(2) O(3) nanoparticles (right) with a room-temperature M(s) of 2.9?emu?g(-1) were synthesized by the thermal decomposition of [Fe(CO)(5) ] but with the stabilizing action of maleic anhydride grafted polypropylene.     

Synthesis and characterization of red-luminescent graphene oxide functionalized with silica-coated Eu3+ complex nanoparticles

Traditional dye-doped fluorescent graphene oxide (GO) reveals a low quantum yield and a short life expectancy. Herein, red-luminescent silica-coated Eu(3+) complex nanoparticles were synthesized and covalently coupled to GO nanosheets by means of a carbodiimide-mediated amidation process. SEM and TEM studies demonstrated successful attachment of the silica-coated Eu(3+) complex nanoparticles onto the GO surface. Spectroscopic studies showed that the GO-nanoparticle conjugates exhibit strong luminescence, long lifetimes, as well as good photostability, which suggests that this new type of luminescent nanomaterial has the potential for highly sensitive time-resolved fluorescence cyto- and histochemistry imaging.     

磁性铁氧化物纳米粒子制备及其体内应用研究

磁性铁氧化物纳米粒子由于其生物相容性和低毒性而广泛的应用于生物医学领域。本文总结了近年来制备各种磁性铁氧化物纳米粒子的方法,比较了它们在粒径、结晶度以及制备条件等方面的优缺点,概括了对其进行表面修饰改性材料的种类,阐述近年来磁性铁氧化物纳米粒子在体内应用中药物运输、磁共振成像、磁热疗方面的进展,并指出当前应用中的主要方向和亟待解决的问题。     

Spectroscopic investigation of the adsorption mechanisms of polyacrylamide polymers onto iron oxide particles

The mechanisms of high-molecular-weight polyacrylamide nonionic homopolymer and 25 mol% anionic acrylate-substituted copolymer adsorption onto iron oxide particles were investigated via DRIFT and UV-vis spectroscopies at three pH values (6, 8.5, and 11). While electrostatic interactions play an important role in charged polymer adsorption, this information is not spectroscopically available. At pH values above and below pH 8.5 (the isoelectric point for the anionic polymer), bidentate chelation and hydrogen bonding were the main adsorption mechanisms. At the isoelectric point, monodentate chelation was observed to be the main mode of adsorption, along with hydrogen bonding. For the nonionic polymer, in all cases, hydrogen bonding through the carbonyl group was the main mode of adsorption. The adsorption of both polymers conformed well to the Freundlich model, suggesting that the adsorbed polymer amount increases with increasing polymer concentration up to 7500 g/t solid, rather than approaching monolayer coverage. Spectroscopic evidence was found to suggest that hydrolysis of nonionic polyacrylamide occurs at high pH.     

Amplified fluorescence response of chemosensors grafted onto silica nanoparticles

In conventional fluorescent chemosensors, the recognition of the target by the receptor unit affects the fluorescence properties of a single covalently coupled fluorescent moiety. Here we show for the first time that when a suitable TSQ derivative is densely grafted onto the surface of preformed silica nanoparticles electronic interactions between the individual chemosensor units enable the free units to recognize the state of the surrounding complexed ones. As a result, the fluorescence transduction is not limited to the local site where binding occurs, but it involves a wider region of the fluorophore network that is able to transfer its excitation energy to the complexed units. Such behavior leads to an amplification of the fluorescence signal. What we report here is the first example of amplification in the case an off-on chemosensor due to its organization onto the surface of silica nanoparticles. We also describe a simple general model to approach amplification in multifluorophoric systems based on the localization of the excited states, which is valid for assemblies such as the supramolecular ones where molecular interactions are weak and do not significantly perturb the individual electronic states. The introduction of an amplification factor f in particular allows for a simple quantitative estimation of the amplification effects.     

Synthesis and characterization of thermosensitive interpenetrating polymer networks based on N-isopropylacrylamide/N-acryloxysuccinimide, crosslinked with polylysine, grafted onto polypropylene

Interpenetrating polymer networks (IPNs) based on poly (N-isopropylacrylamide), (PNIPAAm) and poly (N-acryloxysuccinimide) (PNAS), grafted onto polypropylene (PP), were synthesized in three consecutive steps using ionizing radiation in the first and second steps and chemical reaction in third one. In the first step a thermosensitive graft copolymer of NIPAAm onto PP film was obtained by gamma radiation with a ⁶⁰Co source. The grafted side chains of PNIPAAm were then crosslinked with gamma radiation to give net-[PP-g-NIPAAm]. The secondary network was obtained in situ by chemical crosslinking between PNAS and polylysine (pLys). The PP-g-IPNs exhibited the lower critical solution temperature (LCST) at around 32 °C. Based on its thermoreversible behavior, this system could be used for immobilization of biomolecules. The phase transition temperature (LCST) and network properties of the IPNs were measured by swelling behavior. Additional characterization by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and infrared (FTIR-ATR) determinations are reported.     

Electroanalytical detection of heavy metals using metallophthalocyanine and silica-coated iron oxide composites

The monitoring of heavy metal ions particularly in water is important in safeguarding the environment and humans from the toxic effects these metal ions pose. This work describes the synthesis, characterization and electrocatalytic properties of silica-coated iron oxide nanoparticles (Si-NP) in the presence of cobalt or iron phthalocyanines (MPc) for heavy metal (HM) detection. TEM, XRD, XPS and VSM confirmed the successful synthesis of Si-NP with an average diameter of 12.07 nm. The electrochemical sensing properties of MPc/Si-NP-modified glassy carbon electrodes (GCE) were assessed for HM detection. Differential pulse anodic stripping voltammetry (DPASV) studies indicated detection limits that compared positively with the literature. The FePc/Si-NP composite showed the lowest detection limits (S/N?=?3) of 3.66, 11.56, 2.28, 4.54 μg L^?1 for arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb), respectively. A linear working range of 10–100 μg L^?1 was obtained for As³⁺, Hg²⁺ and Pb²⁺ ions while it was between 20 and 100 μg L^?1 for Cd²⁺ ions. Both composites displayed reproducible signals for the simultaneous detection of the HMs for ten consecutive scans. These composites offer a cheap and simplistic sensing device for HM analysis.     

Preparation of thermosensitive polymer nanoparticles by protein-mimetic cross-linking

Thermosensitive nanoparticles were prepared by mimicking protein folding where polymer aggregates were formed by precipitation of thermosensitive polymer chains followed by disulfide formation of their thiol groups. N-Isopropylacrylamide (NIPAM) and methacryloxy succinimide (SuMA) were co-polymerized and then cysteamine was allowed to react with succinimide moieties of the polymer to render thiol moieties. A polymer aqueous solution precipitated to form nano-sized aggregates by increasing temperature above its lower critical solution temperature (LCST), and their sizes were monodispersed and tunable by the polymer concentration. The aggregates were cross-linked to produce nanoparticles by oxidation of thiol groups in a manner similar to formation of a disulfide bond of protein. As a result, the cross-linked nanoparticles exhibited swelling by decreasing temperature below the LCST of the copolymer. Fluorescein and bovine serum albumin (BSA) were chosen as a small and a large substance, respectively, and were encapsulated into the swollen nanoparticles at 25?°C. Fluorescein was rapidly released from both swollen and shrunken nanoparticles. Although BSA exhibited little release at any temperatures, it was released from nanoparticles by adding the reducing agent to dissociate the disulfide cross-linking and incubating below the LCST.     

Cu immobilized on chitosan-modified iron oxide magnetic nanoparticles: Preparation,characterization and investigation of its anti-lung cancer effects

Chitosan is a linear polysaccharide and non-toxic bioactive polymer with a wide variety of applications due to its functional properties such as ease of modification, and biodegradability. In this study, a green protocol for supporting of Cu(II) on chitosan-encapsulated magnetic Fe₃O₄ nanoparticles is described. The morphological and physicochemical features of the material were determined using several advanced techniques like fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The average diameter of the NPs was approximately 15–25 nm. In addition, the Fe₃O_/CS/Cu(II) nanocomposite was engaged in biological assays like study of anti-oxidant properties by DPPH mediated free radical scavenging test using BHT as a reference molecule. Thereafter, on having a significant IC₅₀ value in radical scavenging assay, we extended the bio-application of the desired nanocomposite in anticancer study of lung well-differentiated bronchogenic adenocarcinoma, lung moderately differentiated adenocarcinoma, and lung poorly differentiated adenocarcinoma of human lung in-vitro conditions. In the cytotoxicity and anti-human lung studies, the nanocomposite was treated to lung cancer lung well-differentiated bronchogenic adenocarcinoma (HLC-1), lung moderately differentiated adenocarcinoma (LC-2/ad), and lung poorly differentiated adenocarcinoma (PC-14) cell line following MTT assay. The cell viability of malignant lung cell line reduced dose-dependently in the presence of Fe₃O_/CS/Cu(II) nanocomposite. The recent results suggest that Fe₃O_/CS/Cu(II) nanocomposite have a suitable anticancer activity against lung cell lines.     

Preparation and conductivities of polyacrylic acid/polyvinylimidazole grafted and ungrafted iron oxide nanocomposite polymer electrolytes

Nanocomposites of Polyacrylic acid/polyvinylimidazole (PAA/PVI) with grafted and ungrafted iron oxide nanoparticles were prepared by a Reflux method. The Fe₃O₄ nanoparticles with 10 nm average diameter were synthesized by controlled co-precipitation and silanization of Si-PVI on Fe₃O₄ was used to obtain the grafted ones. Grafting becomes important at composites of less PVI that cause drastic decreases in AC conductivity. The content of PVI has important effects on the conductivity mechanism of these composites. The effect of grafting and Polyacrylic acid/polyvinylimidazole molar ratio on the conduction mechanism were studied. The conduction mechanism of iron oxide nanocomposites can be adjusted by changing molar ratio of Polyacrylic acid/polyvinylimidazole and grafting of Fe₃O₄ NPs.      

接枝物EVA-g-PBMA的合成及表征

本文合成了具有端羟基的聚甲基丙烯酸丁酯(PBMA-OH),并通过与MA反应,实现了端羟基转化,为接枝EVA水解产物起到了“搭桥”的作用。通过H^1 NMR对不同水解度的EVA皂化产物进行了序列结构剖析,并合成了新型接枝物EVA-g-PBMA。     

Synthesis and characterization of variable-architecture thermosensitive polymers for complexation with DNA

Copolymers of N-isopropylacrylamide with a fluorescent probe monomer were grafted to branched poly(ethyleneimine) to generate polycations that exhibited lower critical solution temperature (LCST) behavior. The structures of these polymers were confirmed by spectroscopy, and their phase transitions before and after complexation with DNA were followed using ultraviolet and fluorescence spectroscopy and light scattering. Interactions with DNA were investigated by ethidium bromide displacement assays, while temperature-induced changes in structure of both polymers and polymer-DNA complexes were evaluated by fluorescence spectroscopy, dynamic light scattering, laser Doppler anemometry, and atomic force microscopy (AFM) in water and buffer solutions. The results showed that changes in polymer architecture were mirrored by variations in the architectures of the complexes and that the overall effect of the temperature-mediated changes was dependent on the graft polymer architecture and content, as well as the solvent medium, concentrations, and stoichiometries of the complexes. Furthermore, AFM indicated subtle changes in polymer-DNA complexes at the microstructural level that could not be detected by light scattering techniques. Uniquely, variable-temperature aqueous-phase AFM was able to show that changes in the structures of these complexes were not uniform across a population of polymer-DNA condensates, with isolated complexes compacting above LCST even though the sample as a whole showed a tendency for aggregation of complexes above LCST over time. These results indicate that sample heterogeneities can be accentuated in responsive polymer--DNA complexes through LCST-mediated changes--a factor that is likely to be important in cellular uptake and nucleic acid transport.     

Hamaker constants of iron oxide nanoparticles

The Hamaker constants for iron oxide nanoparticles in various media have been calculated using Lifshitz theory. Expressions for the dielectric responses of three iron oxide phases (magnetite, maghemite, and hematite) were derived from recently published optical data. The nonretarded Hamaker constants for the iron oxide nanoparticles interacting across water, A(1w1) = 33 - 39 zJ, correlate relatively well with previous reports, whereas the calculated values in nonpolar solvents (hexane and toluene), A(131) = 9 - 29 zJ, are much lower than the previous estimates, particularly for magnetite. The magnitude of van der Waals interactions varies significantly between the studied phases (magnetite < maghemite < hematite), which highlights the importance of a thorough characterization of the particles. The contribution of magnetic dispersion interactions for particle sizes in the superparamagnetic regime was found to be negligible. Previous conjectures related to colloidal stability and self-assembly have been revisited on the basis of the new Lifshitz values of the Hamaker constants.     

Synthesis and characterization of iron oxide/polymer composite nanoparticles with pendent functional groups

We describe in this paper an approach to synthesize superparamagnetic iron oxide nanoparticles in the presence of polymerized lactic acid. The resulted particles consisted of clusters of iron oxide monocrystals, embedded inside the polymer chains. The composite particles synthesized in situ were highly dispersible in aqueous solution with good stability. X-ray diffraction and magnetometer data all confirmed the crystalline structure and super-paramagnetic property of the particles. They exhibited narrow size distribution with hydrodynamic diameters close to 80 nm. In addition, the particles were shown to have abundant surface carboxyl groups, which can be used to conjugate various biomolecules. Such a preparation would be especially useful for developing target specific MRI contrast agents or drug delivery vehicles.     

Chemical grafting of a DNA intercalator probe onto functional iron oxide nanoparticles: a physicochemical study

Spherical magnetite nanoparticles (MNPs, ～ 24 nm in diameter) were sequentially functionalized with trimethoxysilylpropyldiethylenetriamine (TMSPDT) and a synthetic DNA intercalator, namely, 9-chloro-4H-pyrido[4,3,2-kl]acridin-4-one (PyAcr), in order to promote DNA interaction. The designed synthetic pathway allowed control of the chemical grafting efficiency to access MNPs either partially or fully functionalized with the intercalator moiety. The newly prepared nanomaterials were characterized by a range of physicochemical techniques: FTIR, TEM, PXRD, and TGA. The data were consistent with a full surface coverage by immobilized silylpropyldiethylenetriamine (SPDT) molecules, which corresponds to ～22,300 SPDT molecules per MNP and a subsequent (4740-2940) PyAcr after the chemical grafting step (i.e., ～ 2.4 PyAcr/nm(2)). A greater amount of PyAcr (30,600) was immobilized by the alternative strategy of binding a fully prefunctionalized shell to the MNPs with up to 16.1 PyAcr/nm(2). We found that the extent of PyAcr functionalization strongly affects the resulting properties and, particularly, the colloidal stability as well as the surface charge estimated by ζ-potential measurement. The intercalator grafting generates a negative charge contribution which counterbalances the positive charge of the single SPDT shell. The DNA binding capability was measured by titration assay and increases from 15 to 21.5 μg of DNA per mg of MNPs after PyAcr grafting (14-20% yield) but then drops to only ～2 μg for the fully functionalized MNPs. This highlights that even if the size of the MNPs is obviously a determining factor to promote surface DNA interaction, it is not the only limiting parameter, as the mode of binding and the interfacial charge density are essential to improve loading capability.     

Preparation, characterization, and catalytic activity of rare earth metal oxide nanoparticles

In present study, a series of rare earth metal oxide (CeO₂, Pr₂O₃, and Nd₂O₃) nanoparticles have been prepared by sol–gel route using Ce(NO₃)₃·6H₂O, Pr(NO₃)₃·6H₂O and Nd(NO₃)₃·6H₂O, and citric acid as precursor materials. Powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are employed to characterize the size and morphology of the nano oxide particles. The particles are spherical in shape and the average particle size is of the order of 11–30 nm. Their catalytic activity was measured on the thermal decomposition of ammonium perchlorate and composite solid propellants (CSPs) by thermogravimetry (TG), TG coupled with differential thermal analysis (TG–DTA), and ignition delay measurements. The ignition delays and activation energies are found to decrease when rare earth metal oxide nanoparticles were incorporated in the system. Addition of metal oxide nanoparticles to AP led to shifting of the high temperature decomposition peak toward lower temperature and the burning rate of CSPs was also found to enhance. However, E _a activation energy for decomposition was also found to decrease with each catalyst.     

Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles

The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant.