Navegando por Autor "Freitas, Erico Tadeu Fraga"

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An efficient and simple procedure to prepare chemically stable and partially carbon-cleaned magnetite from solid-state synthesis for clinical practices in medical oncology.
(2020) Andrade, Ângela Leão; Almeida, Katia Júlia de; Freitas, Erico Tadeu Fraga; Mesquita, Aline M.; Pereira, Márcio César; Fabris, José Domingos; Fernandez Outon, Luis Eugenio; Ardisson, José Domingos; Domingues, Rosana Zacarias
As far as medical applications for clinical diagnosis and therapy in oncology are concerned, the use of stables magnetic nanoparticles relies on the magnetocaloric response of their ferrofluid suspensions to an applied alternating current magnetic field. To assure their effectiveness as an advanced material for such a medical technology, some critical properties, as any tendency of the nanoparticles to self-agglomerate and of the mag netic core component to somehow change their chemical nature, must be rigorously inhibited. A sample of chemically stable nanoparticles of magnetite ( Fe3+ 2 Fe2+O2− 4 ) was synthesized through the method consisting of burning a synthetic commercial maghemite (γFe3+ 2 O2− 3 ) with admixed sucrose, to partially reduce Fe3+ → Fe2+. The residual carbon, formed on burning the sucrose, tends to coat the nanoparticles and acts as a protective layer hindering the freshly synthesized hot magnetite from being promptly re-oxidized, on cooling the sample in the open-air atmosphere. As a drawback, this carbon layer tends to be a thermal insulator and must be removed, in order to make the magnetite nanoparticles able to be used as a magnetocaloric material and dissipate heat. A chemically gentle removal of the residual carbon was assayed by treating the sample with H2O2 under stirring or sonication either for 30 min or 60 min. The intrinsic atomic and crystalline structures and other essential properties of this core-shell system were assessed by gas adsorption analysis (BET), powder X-ray diffraction, Fourier-transform infrared spectrometry, Mossbauer ¨ spectroscopy and transmission electron microscopy. Theo retical analyses based on the density functional theory (DFT) were used to interpret the harmonic infrared spectra for the produced magnetite. The efficiency in removing the residual carbon layer formed on the magnetite grain surface was checked by saturation magnetization measurements and CHN elemental analysis. The heat releasing ability of the prepared magnetic sample was evaluated under an AC-induced magnetic field. These results evidenced that the treatment with H2O2 was efficient enough to remove, even though not completely, most of the residual carbon layer, which made the saturation magnetization and the heat released by the treated samples significantly greater than that of the untreated carbon-coated grains. The resulting nano magnetite was found to be a sufficiently clean material for being used for hyperthermia-based procedures, particularly for medical diagnosis and therapy, in oncology.
Equisetum hyemale‑derived unprecedented bioactive composite for hard and soft tissues engineering.
(2022) Silva, Rosangela Maria Ferreira da Costa e; Diniz, Ivana Márcia Alves; Gomes, Natália Aparecida; Silva, Guilherme Jorge Brigolini; Ferreira, José Maria da Fonte; Freitas Filho, Rubens Lucas de; Freitas, Erico Tadeu Fraga; Martins, Darliane Aparecida; Domingues, Rosana Zacarias; Andrade, Ângela Leão
Although Bioactive Glasses (BGs) have been progressively optimized, their preparation often still involves the use of toxic reagents and high calcination temperatures to remove organic solvents. In the present work, these synthesis related drawbacks were overcome by treating the ashes from the Equisetum hyemale plant in an ethanol/water solution to develop a bioactive composite [glass/ carbon (BG-Carb)]. The BG-Carb was characterized by scanning electron microscopy, and transmission electron microscopy; and its chemical composition was assessed by inductively coupled plasmaoptical emission spectroscopy. Brunauer–Emmett–Teller gas adsorption analysis showed a specifc surface area of 121 m2 g−1. The formation of hydroxyapatite (HA) surface layer in vitro was confrmed by Fourier-transform infrared spectroscopy analysis before and after immersion in simulated body fuid (SBF) solution. The Rietveld refnement of the XRD patterns and selected area electron difraction analyses confrmed HA in the sample even before immersing it in SBF solution. However, stronger evidences of the presence of HA were observed after immersion in SBF solution due to the surface mineralization. The BG-Carb samples showed no cytotoxicity on MC3T3-E1 cells and osteodiferentiation capacity similar to the positive control. Altogether, the BG-Carb material data reveals a promising plant waste-based candidate for hard and soft tissue engineering.
Preparation of hybrid nanocomposite particles for medical practices.
(2021) Machado, Vagner de Oliveira; Andrade, Ângela Leão; Fabris, José Domingos; Freitas, Erico Tadeu Fraga; Ferreira, José Maria da Fonte; Simon, Alice; Domingues, Rosana Zacarias; Fernandez Outon, Luis Eugenio; Carmo, Flávia Almada do; Souza, Antônio Carlos dos Santos; Cardoso, Hugo Saba Pereira
This study addresses the preparation of hybrid nanoparticles comprised of magnetite (Fe3O4) cores and a surface functionalized with tetramethylammonium hydroxide (TMAOH). The stabilized core nanoparticles were subse quently coated with a polymer matrix consisting of poly(L-co-D,L lactic acid-co-trimethylene carbonate) and poly (ethylene oxide) − poly(propylene oxide) − poly(ethylene oxide) triblock copolymer. The novel core/shell hybrid nanoparticles combine the concepts of electromagnetic heating by the magnetite cores with the drug storage and release ability of the polymeric shell. These multifunctional hybrid nanoparticles are intended for hyperthermia clinical protocols in local drug delivery and medical practices in oncology. The essential physical features of these hybrid composite nanoparticles were assessed using an array of appropriate advanced char acterization techniques. The equivalent average diameters of the composite nanoparticles were relatively uni form and their core/shell mass ratio was estimated through thermogravimetric analysis. The weakening of the intermolecular interactions with decreasing thickness of the coating led to a concomitant decrease in the melting temperature of the shell. The polydispersity index data from dynamic light scattering analysis enabled the conclusion that polymeric species contained in 10 mL of the polymeric matrix solution could effectively coat a maximum of core particles contained in 0.5 mL of ferrofluid.
Ultrastructure of the gill ciliary epithelium of Limnoperna fortunei (Dunker 1857), the invasive golden mussel.
(2022) Freitas, Erico Tadeu Fraga; Moreira, Amanda Maria Siqueira; Paula, Rayan Silva de; Andrade, Gabriela Rabelo; Carvalho, Marcela David de; Assis, Paulo Santos; Jorge, Erika Cristina; Cardoso, Antônio Valadão
Background: Limnoperna fortunei is a freshwater bivalve mollusc originally from southern Asia that invaded South America in the 1990’s. Due to its highly efcient water pumping and fltering, and its capacity to form strong adhe- sions to a variety of substrates by byssus thread, this invasive species has been able to adapt to several environments across South America, causing signifcant ecological and economic damages. By gaining a deeper understanding of the biological and ecological aspects of L. fortunei we will be able to establish more efective strategies to manage its invasion. The gills of the mollusc are key structures responsible for several biological functions, including respiration and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using light microscopy, transmission and scanning electron microscopies. This is the frst report of the morphology of the epithe- lial cells and cilia of the gill of L. fortunei visualized in high resolution. Results: The analysis showed highly organized and abundant ciliary structures (lateral cilia, laterofrontal cirri and fron- tal cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen granules were abundantly found in the epithelial cells of the gills, demonstrating the energy-demanding function of these structures. Neutral mucopolysaccharides (low viscosity mucus) were observed on the frontal surface of the gill flaments and acid mucopolysaccharides (high viscosity mucus) were observed to be spread out, mainly on the lateral tract. Spherical vesicles, possibly containing mucus, could also be observed in these cells. These fndings demonstrate the importance of the mucociliary processes in particle capture and selection. Conclusions: Our data suggest that the mechanism used by this mollusc for particle capture and selection could contribute to a better understanding of key aspects of invasion and also in the establishment of more efcient and economically viable strategies of population control.