Degradação de corantes reativos por processo foto-fenton envolvendo o uso de peneira molecular 4A modificada com Fe3+

In this work the preparation and characterization of a supported catalyst intended for degradation of reactive dyes by Fenton-like processes is described. The photocatalyst was prepared by immobilization of Fe3+ into the molecular sieve (4A type) surface and characterized by x-ray diffractometry and infrared, Mössbauer and EPR spectroscopy. The solid containing 0.94% (w/w) of ferric ions was used in degradation studies of aqueous reactive-dyes samples with really promissory results. Generally, Vis-assisted photochemical processes leads to almost total decolorization of all tested dyes at reaction times lower than 30 min. It was also observed that the iron-molecular sieve matrix can be reused

Doxorubicin-Loaded Iron Oxide Nanoparticles Induce Oxidative Stress and Cell Cycle Arrest in Breast Cancer Cells

Cancer is one of the most common diseases nowadays and derives from the uncontrollable growth of a single cell. Magnetic nanoparticles (NpMag) offer various possibilities for use in the biomedical area, including drug delivery mediated by magnetic fields. In the current study, we evaluated the in vitro effects of iron-oxide magnetic nanoparticles conjugated with the antitumor drug doxorubicin (Dox) on human breast cancer cells. Our results revealed that magnetic nanoparticles with Dox (NpMag+Dox) induce cellular redox imbalance in MCF-7 cells. We also demonstrate that iron-oxide nanoparticles functionalized with Dox induce oxidative stress evidenced by DNA damage, lipid peroxidation, cell membrane disruption, and loss of mitochondria potential. As a result, NpMag+Dox drives MCF-7 cells to stop the cell cycle and decrease cell migration. The association of NpMg+Dox induced a better delivery of Dox to MCF cells, mainly in the presence of a magnetic field, increasing the death of MCF cells which might reduce the toxicity for healthy cells providing a better efficacy for the treatment. Thus, iron-oxide nanoparticles and doxorubicin conjugated may be candidate for anticancer therapy

Caracterização e propriedades do material coloidal nanoestruturado β-FeOOH/bentonita

A new mixed material was obtained through the combination of the suspensions of iron oxy-hydroxide and bentonite clay, denoted BFe. Analysis of its structure (XRD, Mossbauer and TGA) and composition (AAS) suggests the maintenance of the layer structure of the clay and an increase in the thermal stability of the BFe. Electrochemical studies performed in different electrolytes show that only in an alkaline medium it is possible to observe the redox peaks relative to the processes involving Fe+2/Fe+3 pair. Tests that evaluated the potential use of the photo-Fenton process showed an efficient degradation process of the dyes in significantly reduced reaction times

Structural and Mössbauer characterization of the ball-milled Fe/sub x/(Al/sub 2/O/sub 3)/sub 100-x/ system

Metal-oxide composites were synthesized by high-energy ball milling of metallic iron (α-Fe) and alumina (α-Al2O3) powders, varying the starting relative concentration and the milling time. The samples were characterized by scanning electron microscopy, x-ray diffraction, and Mössbauer spectroscopy. The results revealed the formation of a FeAl2O3+W spinel phase (hercynite) and of iron (super)paramagnetic nanoprecipitates, in addition to residual magnetic iron and alumina. We also observed that the relative amounts of nanoprecipitates and hercynite for isochronally milled samples were correlated with the sample nominal concentration x, with the precursor iron being relatively more converted in those phases for low x values. Particularly for x=10 milled sample, the relative amounts of the (super)paramagnetic and spinel phases were observed to increase linearly with the milling time. An x=20/24 h milled sample was annealed in H2 atmosphere and revealed the reduction of hercynite, with iron phase separation

Mechanical milling of the (a-Fe2O3)x(a-Al2O3)1 x system : an x-ray diffraction and Mössbauer spectral study

The system (a-Fe2O3)x(a-Al2O3)1 x was subjected to 24 h of high-energy ball-milling in different milling media and velocities, with x varying in the 0.10 – 0.50 range. Stainless-steel vial with stainless-steel balls and alumina vial with zirconia rods were alternately used in a planetary mill apparatus, at velocities ranging from 100 to 600 rpm. The phases present in the milled samples were characterized by X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). For the stainless-steel milling medium, the results revealed that the final products are extremely dependent on the starting concentration of hematite and on the milling velocity. Iron contamination, originated from abrasion in the metallic medium (MM), was detected for low x and, also, for intermediate x at higher milling velocities. Solid solutions of the (Fe,Al)2O3 type, with different iron concentration ranges, were identified in both milling media. In the ceramic vial, a medium in which milling velocity is also found to be a decisive factor, the FeAlO3 phase, non-isostructural to the precursors, was also recognized in addition to solid solutions. Low-temperature Mössbauer measurements verified the occurrence of four magnetic iron sites in this compound

In situ synthesis of Fe 3 O 4 nanoparticles coated by chito-oligosaccharides: physico-chemical characterizations and cytotoxicity evaluation for biomedical applications

International audienceFe 3 O 4 nanoparticles coated with chito-oligosaccharides (COS) were prepared in situ by a simple co-precipitation method through a mixing of iron ions (Fe 3+ and Fe 2+) and COS aqueous solutions followed by precipitation with ammonia. The impact of COS with different degree of polymerization (DP 10, 24 and 45) and degree of Nacetylation (DA) ∼ 24 and 50 % (exhibiting high solubility) on the synthesis and physical properties of the coated magnetic nanoparticles was evaluated. Several advantages were found when the magnetic nanoparticles were prepared in the presence of the studied COSs, such as: preparation of functionalized magnetic nanoparticles with narrower size distributions and, consequently, higher saturation magnetization (an increase of up to 22%); and an expressive increasing in the concentration of COS-coated magnetic nanoparticles (up to twice) in the cell viability test in comparison with pure Fe 3 O 4 nanoparticles. Furthermore, among the analyzed samples, the magnetic nanoparticles coated by COS with DA ∼ 50 % present a higher cytocompatibility. Our results allow envisioning various biomedical applications, valorizing the use of coated-magnetic nanoparticles for magneticfield assisted drug delivery, enzyme or cell immobilization, or as a marker for specific cell tracking, among others