Synthesis,characterization and MRI application of dextran-coated Fe3O4 magnetic nanoparticles

Biocompatible ferrofluid based on dextran-coated Fe₃O₄ magnetic nanoparticles (MNPs) was prepared through a one-step method. In contrast to the conventional co-precipitation method, hydrazine hydrate was added as reducing agent and precipitator in the present investigation. The effects of hydrazine hydrate, the weight ratio of dextran to MNPs and the molecular weight of dextran on the dispersibility of MNPs in water were investigated. Also, the particles size of modified MNP and coating efficiency of dextran on MNPs were measured. In addition, biocompatible ferrofluid was intravenously injected into rabbits, the iron content in blood and organs at different times were measured by atomic absorption spectrometer, and the bio-distribution and the bio-transportation of ferrofluid in organs was examined. Then, the magnetic resonance (MR) images of liver, marrow and lymph were acquired by MRI experiments before and after intravenous injection of ferrofluid. Image analysis revealed that the MR signal intensity of these organs notably decreased after intensified by ferrofluid. However, when there existed tumors in organs, the signal intensity of tumor did not change after injection. From that the tumor can easily be identified, which indicated a potential application of the as-prepared MNP in functional molecular imaging for biomedical research and clinical diagnosis.     

Evaluation of Fe(III)EDTA and Fe(II)EDTA-NO reduction in a NO x scrubber solution by magnetic Fe3O4-chitosan microspheres immobilized microorganisms

A two-stage bioreduction system containing magnetic-microsphere-immobilized denitrifying bacteria and iron-reducing bacteria was developed for the regeneration of scrubbing solutions for NO _x removal. In this process, a higher bioreduction rate and a better tolerance of inhibition of bacteria were achieved with immobilized bacteria than with free bacteria. This work focused on evaluation of the effects of the main components in the scrubbing solution on Fe(III)EDTA (EDTA: ethylenediaminetetraacetate) and Fe(II)EDTA-NO reduction, with an emphasis on mass transfer and the kinetic model of Fe(III)EDTA and Fe(II)EDTA-NO reduction by immobilized bacteria. It was found that Fe(II)EDTA-NO had a strong inhibiting effect, but Fe(II)EDTA had no effect, on Fe(III)EDTA reduction. Fe(II)EDTA accelerated Fe(II)EDTA-NO reduction, whereas Fe(III)EDTA had no effect. This showed that the use of the two stages of regeneration was necessary. Moreover, the effect of internal diffusion on Fe(III)EDTA and Fe(II)EDTANO reduction could be neglected, and the rate-limiting step was the bioreduction process. The reduction of Fe(III)EDTA and Fe(II)EDTA-NO using immobilized bacteria was described by a first-order kinetic model. Bioreduction can therefore be enhanced by increasing the cell density in the magnetic chitosan microspheres.     

High activity and selectivity immobilized lipase on Fe3O4 nanoparticles for banana flavour synthesis

Lipase (E.C.3.1.1.3) from Thermomyces lanuginosus (TL) was directly bonded, through multiple physical interactions, on citric acid functionalized monodispersed Fe₃O₄ nanoparticles (NPs) in presence of a small amount of hydrophobic functionalities. A very promising scalable synthetic approach ensuring high control and reproducibility of the results, and an easy and green immobilization procedure was chosen for NPs synthesis and lipase anchoring. The size and structure of magnetic nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The samples at different degree of functionalization were analysed through thermogravimetric measurements. Lipase immobilization was further confirmed by enzymatic assay and Fourier transform infrared (FT-IR) spectra. Immobilized lipase showed a very high activity recovery up to 144% at pH = 7 and 323% at pH = 7.5 (activity of the immobilized enzyme compared to that of its free form). The enzyme, anchored to the Fe₃O₄ nanoparticles, to be easy recovered and reused, resulted more stable than the native counterpart and useful to produce banana flavour. The immobilized lipase results less sensitive to the temperature and pH, with the optimum temperature higher of 5 °C and optimum pH up shifted to 7.5 (free lipase optimum pH = 7.0). After 120 days, free and immobilized lipases retained 64% and 51% of their initial activity, respectively. Ester yield at 40 °C for immobilized lipase reached 88% and 100% selectivity.     

Novel and efficient method for immobilization and stabilization of β-d-galactosidase by covalent attachment onto magnetic Fe3O4–chitosan nanoparticles

A novel and efficient immobilization of β-d-galactosidase from Aspergillus oryzae has been developed by using magnetic Fe₃O₄–chitosan (Fe₃O₄–CS) nanoparticles as support. The magnetic Fe₃O₄–CS nanoparticles were prepared by electrostatic adsorption of chitosan onto the surface of Fe₃O₄ nanoparticles made through co-precipitation of Fe²⁺ and Fe³⁺. The resultant material was characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. β-d-Galactosidase was covalently immobilized onto the nanocomposites using glutaraldehyde as activating agent. The immobilization process was optimized by examining immobilized time, cross-linking time, enzyme concentration, glutaraldehyde concentration, the initial pH values of glutaraldehyde and the enzyme solution. As a result, the immobilized enzyme presented a higher storage, pH and thermal stability than the soluble enzyme. Galactooligosaccharide was formed with lactose as substrate by using the immobilized enzyme as biocatalyst, and a maximum yield of 15.5% (w/v) was achieved when about 50% lactose was hydrolyzed. Hence, the magnetic Fe₃O₄–chitosan nanoparticles are proved to be an effective support for the immobilization of β-d-galactosidase.     

Activity of glucose oxidase functionalized onto magnetic nanoparticles

BACKGROUND: Magnetic nanoparticles have been significantly used for coupling with biomolecules, due to their unique properties. METHODS: Magnetic nanoparticles were synthesized by thermal co-precipitation of ferric and ferrous chloride using two different base solutions. Glucose oxidase was bound to the particles by direct attachment via carbodiimide activation or by thiophene acetylation of magnetic nanoparticles. Transmission electron microscopy was used to characterize the size and structure of the particles while the binding of glucose oxidase to the particles was confirmed using Fourier transform infrared spectroscopy. RESULTS: The direct binding of glucose oxidase via carbodiimide activity was found to be more effective, resulting in bound enzyme efficiencies between 94-100% while thiophene acetylation was 66-72% efficient. Kinetic and stability studies showed that the enzyme activity was more preserved upon binding onto the nanoparticles when subjected to thermal and various pH conditions. The overall activity of glucose oxidase was improved when bound to magnetic nanoparticles CONCLUSION: Binding of enzyme onto magnetic nanoparticles via carbodiimide activation is a very efficient method for developing bioconjugates for biological applications.     

3D in silico study of magnetic fluid hyperthermia of breast tumor using Fe3O4 magnetic nanoparticles

Modeling and simulation of the temperature distribution, the mass concentration, and the heat transfer in the breast tissue are hot issues in magnetic fluid hyperthermia treatment of cancer. The breast tissue can be visualized as a porous matrix with saturated blood. In this paper, 3D in silico study of breast cancer hyperthermia using magnetic nanoparticles (MNPs) is conducted. The 3D FEM models are incorporated to investigate the infusion and backflow of nanofluid in the breast tumor, the diffusion of nanofluid, temperature distribution during the treatment, and prediction of the fraction of tumor necrosis while dealing with the thermal therapy. All the hyperthermia procedures are simulated and analyzed on COMSOL Multiphysics. The sensitivity of frequency and amplitude of the applied magnetic field (AMF) is investigated on the heating effect of the tumor. The mesh dependent solution of Penne's bioheat model is also analyzed. The simulated results demonstrate successful breast cancer treatment using MNPs with minimum side effects. Validation of current simulations results with experimental studies existing in literature advocates the success of our therapy. The increase in the amplitude and frequency of the AMF increases of the temperature in the tumor. The variation of mesh from coarser to finer increased the temperature through small fractions. We have also simulated the magnetic induction problem where the magnetic field is generated by current-carrying coil conductors induce heat in nearby breast tumors due to excitation of MNPs by magnetic flux. This research will aid treatment protocols and real-time clinical breast cancer treatments.     

水溶性有机溶剂对Fe3O4磁性纳米粒子过氧化物酶样活性的影响

采用化学共沉淀法合成10nm的Fe3O4磁性纳米粒子(MNPs)。以辣根过氧化物酶(HRP)为对照,研究了四氢呋喃、1,4-二氧六环、丙酮、N,N-二甲基酰胺、甲醇和二甲亚砜等6种水溶性有机溶剂对Fe3O4MNPs过氧化物酶样活性的影响。结果表明,在有机溶剂浓度(V/V)为30%～75%时,Fe3O4MNPs相对酶活力迅速下降至近于完全失活。在15%有机溶液中,Fe3O4MNPs的最适反应温度多为50oC,最适反应pH在3.6左右。经15%有机溶液处理后的水相反应酶活显示,Fe3O4MNPs表现出对有机溶剂较强的热稳定性和pH稳定性,且对75%有机溶液也具有良好的稳定性。以上多数性质均优于相同条件下的HRP组,表明Fe3O4MNPs是一种比HRP对水溶性有机溶剂更稳定的过氧化物酶。由于Fe3O4MNPs具有易制备、成本低、易于磁分离和可循环使用的特点,因此其具有替代HRP用于有机催化的应用潜力。     

Activity and storage stability of immobilized glucose oxidase onto magnesium silicate

Glucose oxidase (GOD) was covalently immobilized onto florisil (magnesium silicate) carrier via glutaraldehyde. Immobilization conditions were optimized: the amount of initial GOD per grams of carrier as 5 mg, pH as 5.5, immobilization time as 120 min and temperature as 10 °C. Under the optimized reaction conditions activities of free and immobilized GOD were measured. Free and immobilized GOD samples were characterized with their kinetic parameters, and thermal and storage stabilities. K_M and V_max values were 68.2 mM and 435 U mg GOD⁻¹ for free and 259 mM and 217 U mg GOD⁻¹ for immobilized enzymes, respectively. Operational stability of the immobilized enzyme was also determined by using a stirred batch type column reactor. Immobilized GOD was retained 40% of its initial activity after 50 reuses. Storage stabilities of the immobilized GOD samples stored in the mediums with different relative humidity in the range of 0–100% were investigated during 2 months. The highest storage stability was determined for the samples stored in the medium of 60% relative humidity. Increased relative humidity from 0% to 60% caused increased storage stability of immobilized GODs, however, further increase in relative humidity from 80% to 100% caused a significant decrease in storage stability of samples.     

Sequential enzymatic reactions and stability of biomolecules immobilized onto phospholipid polymer nanoparticles

Polymer nanoparticles for sequential enzymatic reactions were prepared by combining a phospholipid polymer shell with a polystyrene core. The active ester groups for the bioconjugation and phospholipid polar groups were incorporated into the phospholipid polymer backbone using a novel active ester monomer and 2-methacryloyloxyethyl phosphorylcholine. For the sequential enzymatic reactions, acetylcholinesterase, choline oxidase, and horseradish peroxidase-labeled IgG were immobilized onto the nanoparticles. As substrates, acetylcholine chloride, choline chloride, and tetramethylbenzidine were added to the nanoparticle suspension, the acetylcholine chloride was converted to choline chloride, the choline chloride was oxidized by choline oxidase, and hydrogen peroxide was then formed as an enzymatic degradation product. The hydrogen peroxide was used for the next enzymatic reaction (oxidized by peroxidase) with tetramethylbenzidine. The sequential enzymatic reactions on the nanoparticles via degradation products (hydrogen peroxide) were significantly higher than that of the enzyme mixture. This result indicated that the diffusion pathway of the enzymatic products and the localization of the immobilized enzyme were important for these reactions. These nanoparticles were capable of facilitating sequential enzymatic reactions.     

DBT degradation enhancement by decorating Rhodococcus erythropolis IGST8 with magnetic Fe3O4 nanoparticles

Biodesulfurization (BDS) of dibenzothiophene (DBT) was carried out by Rhodococcus erythropolis IGST8 decorated with magnetic Fe₃O₄ nanoparticles, synthesized in‐house by a chemical method, with an average size of 45–50 nm, in order to facilitate the post‐reaction separation of the bacteria from the reaction mixture. Scanning electron microscopy (SEM) showed that the magnetic nanoparticles substantially coated the surfaces of the bacteria. It was found that the decorated cells had a 56% higher DBT desulfurization activity in basic salt medium (BSM) compared to the nondecorated cells. We propose that this is due to permeabilization of the bacterial membrane, facilitating the entry and exit of reactant and product, respectively. Model experiments with black lipid membranes (BLM) demonstrated that the nanoparticles indeed enhance membrane permeability. Biotechnol. Bioeng. 2009;102: 1505–1512. © 2008 Wiley Periodicals, Inc.     

Loss of myocardial capillary endothelial-cell alkaline phosphatase (ALP) activity in primary endothelial cell culture

Primary cultures of rat myocardial capillary endothelial cells were established and characterized. A range of typical endothelial cell-specific markers were retained in vitro. Cell kinetic studies in confluent endothelial-cell cultures in vitro revealed a roughly 50-fold increase in the proportion of cells in s-phase, indicating a very considerable shortening of cell turnover time, compared to in vivo conditions. Alkaline phosphatase enzyme activity and encoding mRNA are strongly expressed in myocardial capillary endothelial cells in vivo, but were not detectable in vitro. This was true in cell cultures from two strains of rat, which revealed significantly different enzyme expression levels in vivo. In co-cultures of pericytes and endothelial cells, positive ALP enzyme reaction was detected in pericytes, which in vivo show only very weak enzyme reactivity. Treatment of cell cultures with ≤10 M retinoic acid had no effect in pure endothelial cell cultures, but did increase ALP expression of pericytes in co-cultures. The observation of a loss of endothelial ALP expression in vitro supports other in vitro as well as our own in vivo observations, indicating a negative correlation of ALP expression and proliferative activity of endothelial cells.     

Synthesis and characterization of a pH-sensitive conjugate of isoniazid with Fe3O4@SiO2 magnetic nanoparticles

The Letter describes the preparation and characterization of a conjugate of isoniazid (INH) with magnetic nanoparticles Fe₃O₄@SiO₂ 115 ± 60 nm in size. The INH molecules were attached to the surface of nanoparticles by a covalent pH-sensitive amidine bond. The conjugate was characterized by X-ray diffraction, SEM, dynamic light scattering, IR spectroscopy and microanalysis. The conjugate released isoniazid under in vitro conditions (pH = 4; 37 °C; t_1/2 ≈ 115 s). In addition, the cytotoxicity of the Fe₃O₄@SiO₂–INH conjugate was evaluated in SK-BR-3 cells using the xCELLigence system.     

Ultrastructural demonstration of alkaline phosphatase (ALP) and K+-p-nitrophenyl phosphatase (K+-p-NPPase) in the epidermal ionocytes of Blennius sanguinolentus

Summary Cytochemical techniques were used for the light and electron microscopical localization of alkaline phosphatase and potassium-dependent nitrophenyl phosphatase in the epidermal ionocytes of the Teleost Blennius sanguinolentus.The heavier deposition of the reaction products obtained with the different media was shown in the cytoplasmic surface of the labyrinth tubules, the apical vesicles and in intimate association with plasmic membranes. Both plasma membranes and intracellular activities are affected by the addition of specific inhibitors l-p-bromotetramisole oxalate and ouabain) to both complete and control media.The significance of the cytoplasmic localization of both the two enzymes is discussed with reference to current models of transepithelial ion transportation.     

Ultrastructural demonstration of alkaline phosphatase (ALP) and K+-p-nitrophenyl phosphatase (K+-p-NPPase) in the epidermal ionocytes of Blennius sanguinolentus

Cytochemical techniques were used for the light and electron microscopical localization of alkaline phosphatase and potassium-dependent nitrophenyl phosphatase in the epidermal ionocytes of the Teleost Blennius sanguinolentus. The heavier deposition of the reaction products obtained with the different media was shown in the cytoplasmic surface of the labyrinth tubules, the apical vesicles and in intimate association with plasmic membranes. Both plasma membranes and intracellular activities are affected by the addition of specific inhibitors L-p-bromotetramisole oxalate and ouabain) to both complete and control media. The significance of the cytoplasmic localization of both the two enzymes is discussed with reference to current models of transepithelial ion transportation.     

Synthesis of ethyl (R)-4-chloro-3-hydroxybutyrate by immobilized cells using amino acid-modified magnetic nanoparticles

Fe₃O₄-Arg was selected as the optimal carrier due to its high activity recovery of immobilized cells in the preparation of Fe₃O₄-Arg-Cells. The optimal immobilization conditions for the preparation of Fe₃O₄-Arg-Cells were 30 °C, 4 h, pH 7, and 3 g dry yeast. The activity recovery of immobilized cells reached 76.8 %. For a batch reduction in a shaker in an alternating magnetic field, Fe₃O₄-Arg-Cells were used as a catalyst to gain ethyl (R)-4-chloro-3-hydroxybutyrate ((R)-CHBE). For further improvement in reduction productivity, a continuous reduction in the magnetic fluidized bed reactor system (MFBRS) was completed. Under their optimal transformation conditions, it took 24 h for Fe₃O₄-Arg-Cells to complete the conversion of ethyl 4-chloro-3-oxobutanoate (COBE) (0.8553 mol/L) in the shaker and only 8 h for the batch reduction in an alternating magnetic field. Continuous reduction in MFBRS provided new ideas for the efficient production of (R)-CHBE; 1.5882 mol/L (10 mL) of COBE can be completely converted in 6 h. The conversion and enantiomeric excess (e.e.) of (R)-CHBE were 100 % and above 99.9 % respectively, in the three reaction systems mentioned above.     

Influence of Fe0 nanoparticles,magnetite Fe3O4 nanoparticles,and iron (II) sulfate (FeSO4) solutions on the content of photosynthetic pigments in Triticum vulgare

Seeds and seedlings of soft wheat (Triticum vulgare Vill.) were used to study seed germination, leaf elongation, and the content of photosynthetic pigments (chlorophylls a, b and carotenoids) as affected by five concentrations of iron-containing nanoparticles (NP): spherical Fe⁰ NP with the diameter of 80 ± 5 nm and the magnetite Fe₃O₄ NP measuring 50–80 nm in width and 4–10 nm in height. The effects of FeSO₄ solutions were also tested for comparison. The parameters examined varied as a function of the exogenous agent applied, the agent concentration, and the exposure duration. The highest sensitivity of seedlings was observed in the presence of increasing concentrations of iron (II) sulfate in the nutrient medium. This was evident from the decrease in seed germination percentage, inhibition of leaf growth, and the diminished content of photosynthetic pigments. The apparent toxicity of iron nanoforms varied depending on the parameter examined. (1) The strongest inhibition of germination was exerted by Fe⁰ NP (toxicity assessed from germination percentage was 3.3% higher with Fe⁰ NP than with magnetite NP); (2) the inhibition of leaf elongation on the 4th day after germination was most evident in the presence of Fe⁰ NP (a 12% stronger inhibition in the presence of Fe⁰ NP than in the presence of magnetite NP), whereas on the 7th day the inhibition was most pronounced with magnetite NP (a 9% stronger inhibition in the presence of Fe₃SO₄ NP than in the presence of Fe⁰ NP); (3) the lowest total content of photosynthetic pigments on the 4th day of seedling growth was noted in the presence of magnetite NP (8% lower in the presence of Fe₃SO₄ NP than in the presence of Fe⁰ NP), whereas on the 7th day the lowest pigment pool was observed in the presence Fe⁰ NP (a 3% reduction compared to that in the presence of magnetite NP). The highest content of photosynthetic pigments was recorded in the presence of 0.125 and 0.001 g/L of Fe⁰ NP, 0.5 g/L and 1 μg/L of Fe₃O₄ NP, and 1 mg/L FeSO₄.